Vapour lock

Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines. It occurs when the liquid fuel changes state from liquid to vapor while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporize due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.


Causes and Incidence

Vapor lock was far more common in older petrol fuel systems incorporating a low-pressure mechanical fuel pump driven by the engine, located in the engine compartment and feeding a carburetor. Such pumps were typically located higher than the fuel tank, were directly heated by the engine and fed fuel directly to the float tank inside the carburetor. Fuel was drawn under negative pressure from the feed line, increasing the risk of a vapor lock developing between the tank and pump. A vapor lock being drawn into the fuel pump could disrupt the fuel pressure long enough for the float chamber in the carburetor to partially or completely drain, causing fuel starvation in the engine. Even temporary disruption of fuel supply into the float chamber is not ideal; most carburetors are designed to run at a fixed level of petrol in the float chamber and reducing the level will reduce the air:fuel mixture delivered.

Carburetor units may not effectively deal with fuel vapor being delivered to the float chamber. Most designs incorporate a pressure balance duct linking the top of the float chamber with either the intake to the carburetor or the outside air. Even if the pump can handle vapor locks effectively, fuel vapor entering the float chamber has to be vented. If this is done via the intake system, the mixture is, in-effect, enriched, creating a mixture control and pollution issue. If it is done by venting to the outside, the result is direct hydrocarbon pollution and an effective loss of fuel efficiency and possibly a petrol odor problem. For this reason, some fuel delivery systems allow fuel vapor to be returned to the fuel tank to be condensed back to the liquid phase. This is usually implemented by removing fuel vapor from the fuel line near the engine rather than from the float chamber. Such a system may also divert excess fuel pressure from the pump back to the tank.

Most modern engines are equipped with fuel injection, and have a high pressure electric fuel pump in the fuel tank. Moving the fuel pump to the interior of the tank helps prevent vapor lock, since the entire fuel delivery system is under high pressure and the fuel pump runs cooler than if it is located in the engine compartment. This is the primary reason that vapor lock is rare in modern fuel systems. For the same reason, some carbureted engines are retrofitted with an electric fuel pump near the fuel tank.

Other solutions to vapor lock are rerouting of the fuel lines away from heat generating components, installation of a fuel cooler or cool can, shielding of heat generating components near fuel lines, and insulation of fuel lines.

A vapor lock is more likely to develop when the vehicle is in traffic because the under-hood temperature tends to rise. A vapor lock can also develop when the engine is stopped while hot and the vehicle is parked for a short period. The fuel in the line near the engine does not move and can thus heat up sufficiently to form a vapor lock. The problem is more likely in hot weather or high altitude in either case.


Incidence with other fuels

The higher the volatility of the fuel, the more likely it is that vapor lock will occur. Historically, gasoline (petrol) was a more volatile distillate than today and was more prone to vapor lock. Conversely, fuel for diesel engines is far less volatile than petrol and thus these engines hardly ever suffer from vapor lock. However, diesel engine fuel systems are far more susceptible to air locks in their fuel lines as standard diesel fuel injection pumps rely on the fuel being non-compressible. Air locks are caused by air leaking into the fuel delivery line or from the tank rather than the fuel evaporating in them. Eliminating such air locks requires an extended period of turning over the engine using the starter motor or manually bleeding the system.

Warm air intake

A warm air intake, or WAI, is a system to decrease the amount of air going into a car for the purpose of increasing the fuel efficiency of the internal-combustion engine.

All warm air intakes operate on the principle of decreasing the air density and therefore the amount of oxygen available for combustion with fuel. Warm air from inside the engine bay is used opposed to air taken from the stock intake which may pull in colder (and more dense) air.

It is similar to a cold air intake (CAI), which significantly differs by collecting air from a colder source outside of the engine bay where the air has a higher density and therefore more oxygen.

BMW M1

The BMW M1 is a supercar produced by the German automaker BMW from 1978 to 1981. It was the first and only mid-engined BMW. It employed a twin-cam M88/1 3.5 L 6-cylinder gasoline engine, a version of which was later used in the E24 BMW M6/M635CSi and E28 BMW M5. The engine had six separate throttle butterflies, four valves per cylinder and produced 277 PS (204 kW) in the street version, giving a top speed of 260 km/h (162 mph). Turbocharged racing versions were capable of producing around 850 hp.

The M1 coupe was hand-built between 1978 and 1981 under the Motorsport division of BMW as a homologation special for sports car racing. The body was designed by Giugiaro, taking inspiration from the 1972 BMW Turbo show car. Originally, BMW commissioned Lamborghini to work out the details of the car's chassis, assemble prototypes and manufacture the vehicles, but Lamborghini's financial position meant that BMW reassumed control over the project in April 1978, after seven prototypes were built. Only 456 production M1s were built, making it one of BMW's rarest models. The spirit of the M1 lived on in the first-generation M5, as both models shared the same (though slightly modified) engines.

Though the car never saw a great deal of racing success, the M1 is remembered as a refined and civilized supercar in the true BMW tradition, with great handling and stellar build quality. In 2004, Sports Car International named the car number ten on the list of Top Sports Cars of the 1970s.

Coffman engine starter

The Coffman engine starter (also known as a "shotgun starter") was a starting system used on many radial piston engines in aircraft and armored vehicles of the 1930s and 1940s. Most American military aircraft and tanks which used radial engines were equipped with this system. A derivation of the Coffman starter was also used on a number of jet engines, including those used on the Canberra B-57 light bomber.

The device used a blank gunpowder cartridge that, when fired, would cause the propeller to turn over and hopefully start the engine. The other systems used during the period were electric motors (such as those used in automobiles today) inertia starters (cranked either by hand or an electric motor) and compressed-air starters, which operate much like Coffman starters but are powered by pressurized tanks.

Shotgun starters are composed of a breech and a motor, which are connected by a metal line. The cartridge fits into the breech, and is triggered either electrically or mechanically. The expanding gases from the cartridge pressurize the line and cause the motor to spin and engage the starter ring on the engine, which is attached to the crankshaft.

The advantage of the cartridge system over electric starters is that the batteries of the time were weak and trouble-prone. Aircraft with electric motors often required the use of a battery cart and jumper cables, or large, heavy batteries carried in the plane. Inertia starters use a heavy wheel, usually made of brass, which is spun by a hand crank or electric motor, then the spinning wheel is made to engage the starter ring. The Coffman system weighs less.

The primary disadvantages of the shotgun starter are the need to keep a stock of cartridges, one of which is used for each attempt to start, and the short time that the motor is spun by each cartridge. Compressed-air starters, which use the same type of motor, are usually recharged by an engine-driven compressor, negating the need to carry cartridges. Hybrid systems can be made simply by adding a cartridge breech or an air tank to an existing system.

The Coffman starter was the most common brand of cartridge starters during the mid-1930s, and the name was used as a generic description. The starter became famous as a plot device in the movie "Flight of the Phoenix," when pilot James Stewart had a limited number of cartridges with which to start the makeshift aircraft's engine.

Some modern military diesels still use this device, but advances in battery technology have made shotgun starters obsolete for most uses.

Engine test stand

An engine test stand is a facility used to develop, characterize and test engines. The facility, often offered as a product to automotive OEMs, allows engine operation in different operating regimes and offers measurement of several physical variables associated with the engine operation.

A sophisticated engine test stand houses several sensors (or transducers), data acquisition features and actuators to control the engine state. The sensors would measure several physical variables of interest which typically include:

* crankshaft torque

* angular velocity of crankshaft

* intake air and fuel consumption rates, often detected using volumetric and/or gravimetric measurement methods

* air-fuel ratio for the intake mixture, often detected using an exhaust gas oxygen sensor

* environment pollutant concentrations in the exhaust gas such as carbon monoxide, different configurations of hydrocarbons and nitric oxides, sulphur dioxide, and particulate matter

* temperatures and gas pressures at several locations on the engine body such as engine oil temperature, spark plug temperature, exhaust gas temperature, intake manifold pressure

* atmospheric conditions such as temperature, pressure, humidity

Information gathered through the sensors is often processed and logged through data acquisition systems. Actuators allow for attaining a desired engine state (often characterized as a unique combination of engine torque and speed). For gasoline engines, the actuators may include an intake throttle actuator, a loading device for the engine such as an induction motor. The engine test stands are often custom-packaged considering requirements of the OEM customer. They often include a microcontroller based feedback control system with following features:

* closed-loop desired speed operation (useful towards characterization of steady-state or transient engine performance)

* closed-loop desired torque operation (useful towards emulation of in-vehicle, on-road scenarios, thereby enabling an alternate way of characterization of steady-state or transient engine performance)



Engine test stand applications

* Research and Development of engines, typically at an OEM laboratory
* Tuning of in-use engines, typically at service centers or for racing applications
* End of production line at an OEM factory


Engine testing for R&D

Research and Development activities on engines at automobile OEMs have necessitated sophisticated engine test stands. Automobile OEMs are usually interested in developing engines that meet the following three-fold objectives:

* to provide high fuel efficiency
* to improve drivability and durability
* to be in compliance to relevant emission legislation

Consequently, an R&D engine test stands allow for a full-fledged engine development exercise through measurement, control and record of several relevant engine variables.

Typical tests include ones that:

* determine fuel efficiency and drivability: torque-speed performance test under steady-state and transient conditions

* determine durability: aging tests, oil and lubrication tests

* determine compliance to relevant emission legislations: volumetric and mass emission tests over stated emission test cycles

* gain further knowledge about the engine itself: engine mapping exercise or development of multidimensional input-output maps among different engine variables. e.g. a map from intake manifold pressure and engine speed to intake air flow rate.

Brake specific fuel consumption

Brake specific fuel consumption (BSFC) is a measure of an engine's efficiency. It is the rate of fuel consumption divided by the rate of power production. BSFC is specific for the piston engine known as the reciprocating engine. The general term is specific fuel consumption (SFC). There is also thrust specific fuel consumption (TSFC) for turbine and rocket engines.


The BSFC Calculation (in metric units)

To calculate BSFC, use the formula BSFC = Fuel_rate / Power
Where:

Fuel_rate is the fuel consumption in grams per hour (g/hr)
Power is the power produced in Kilowatts where kW = w * Tq / 9549.27

w is the engine speed in rpm
Tq is the engine torque in newton meters (N·m)

Note: The Power in the BSFC calculation is not weather corrected.


The resulting units of BSFC are g/(kW·h)
The conversion between metric and U.S. units is:

BSFC_US(Lbs/(HP*Hr)) * 608.277 = BSFC_METRIC(g/(kW·h))
BSFC_METRIC(g/(kW·h)) * .001644 = BSFC_US(Lbs/(HP*Hr))


To calculate the actual efficiency of an engine requires the energy density of the fuel being used.
Different fuels have different energy densities defined by the fuels lower heating value.

Some examples of lower heating values for vehicle fuels are:

Certification gasoline = 18640 BTU/lb = .01204 kW·h/g
Regular gasoline = 18917 BTU/lb = .0122225 kW·h/g
Diesel fuel = 18500 BTU/lb = .0119531 kW·h/g


Thus a diesel engine's efficiency = 1/(BSFC*.0119531)
and a gasoline engine's efficiency = 1/(BSFC*.0122225)

A typical cycle average value of BSFC for a gasoline engine is 322 g/(kW·h). This means the average efficiency of a gasoline engine is only 25%. A reciprocating engine achieves maximum efficiency when the intake air is unthrottled and the engine speed is at around 2000 rpm. For a gasoline engine, the most efficient BSFC is around 256 g/(kW·h) or an efficiency of 32%. Efficiency is worse at other operating conditions. As you can see above, lower values of BSFC mean higher engine efficiency. Diesel engines are more efficient than gasoline engines. A diesel engine can have a BSFC as low as 199 g/(kW·h) and around 42% efficiency.
See also Fuel economy in automobiles.

Diesel engine Glow Plug

Glow plugs are used to heat the combustion chambers of some diesel engines in cold conditions to help ignition at coldstart. In the tip of the glow plug is a coil of a resistive wire or a filament which heats up when electricity is connected.

Glow plugs are required because diesel engines produce the heat needed to ignite their fuel by the compression of air in the cylinder and combustion chamber. Gasoline engines use an electric spark plug. In cold weather, and when the engine block, engine oil and cooling water are cold, the heat generated during the first revolutions of the engine is conducted away by the cold surroundings, preventing ignition. The glow plugs are switched on prior to turning over the engine to provide heat to the combustion chamber, and remain on as the engine is turned over to ignite the first charges of fuel. Once the engine is running, the glow plugs are no longer needed, although some engines run the glow plugs for between 5 and 10 seconds after starting to ensure smooth and efficient running and sometimes to keep the engine within emissions regulations (combustion efficiency is greatly reduced when the engine is very cold). During this period, the power fed to the glow plugs is greatly reduced to prevent them burning out by overheating.

-injection diesel engines are less thermally efficient due to the greater surface area of their combustion chambers and so suffer more from cold-start problems. They require longer pre-heating times than direct-injection engines, which often do not need glow plugs at all in temperate or hot climates even for a cold start.

In a typical diesel engine, the glow plugs are switched on for between 10 and 20 seconds prior to starting. Older, less efficient or worn engines may need as much as a minute (60 seconds) of pre-heating.

Large diesel engines as used in heavy construction equipment, ships and locomotives do not need glow plugs. Their cylinders are large enough so that the air in the middle of the cylinder is not in contact with the cold walls of the cylinder, and retains enough heat to allow ignition.

automotive diesel engines with electronic injection systems use various methods of altering the timing and style of the injection process to ensure reliable cold-starting. Glow plugs are fitted, but are rarely used for more than a few seconds.

Glow plug filaments must be made of materials such as platinum and iridium that are resistant both to heat and to oxidation and reduction by the burning mixture. These particular materials also have the advantage of catalytic activity, due to the relative ease with which molecules absorbed on their surfaces can react with each other. This aids or even replaces electrical heating.


Model engines

In model aircraft, and similar applications , glow plugs are used for starting as well as continuing the power cycle. The glow plug consists of a durable, mostly platinum, helically wound wire filament, within a cylindrical pocket in the plug body, exposed to the combustion chamber. A small direct current voltage (around 1.5 volts) is applied to the glow plug, the engine is then started, and the voltage is removed. The burning of the fuel/air mixture in a glow-plug model engine, which requires methanol for the glow plug to work in the first place, and sometimes with the use of nitromethane for greater power output, occurs due to the catalytic reaction of the methanol vapor to the presence of the platinum in the filament, thus causing the ignition. This keeps the plug's filament glowing hot, and allows it to ignite the next charge. Since the ignition timing is not controlled electrically, as in a spark ignition engine or by fuel injection, as in an ordinary diesel, it must be adjusted by the richness of the mixture, the ratio of nitromethane to methanol, the compression ratio, the cooling of the cylinder head, the type of glow plug, etc. A richer mixture will tend to cool the filiment and so retard ignition, slowing the engine, and a rich mixture also eases starting. After starting the engine can easily be leaned (by adjusting a needle valve in the spraybar) to obtain maximum power.

Forced induction

Forced induction is a term used to describe internal combustion engines that are not naturally aspirated. Instead, a gas compressor is added to the air intake, thereby increasing the quantity of oxygen available for combustion. This compressed air is normally referred to as Boost or charge air.


Introduction

Forced induction can be used to increase the power of an engine or its efficiency, or both, without much extra weight. The ambient air that the engine is normally ingesting enters the compressor inlet of turbocharger or supercharger that is inline along the air intake tract. This effectively increases the pressure and density of the air, which allows for a much greater percentage of oxygen per volume of air intake to be added to the air/fuel mixture. The effects are an increase to the effective capacity of the engine without an increase in physical size. The forced induction approach has the advantage that the intake pressure may be regulated according to the engine speed, thus providing power from extra capacity at high speed, but without wasting fuel at lower speeds. A Nitrous Oxide system is also a form of forced induction. A simple oxidizer is injected either directly (direct port) or by a single fogger...with fuel(wet nitrous system) or without fuel(dry nitrous system).

Two of the commonly used forced induction technologies are turbochargers and superchargers. They differ mainly in the power source for the compressor. Turbochargers are driven by the exhaust gases of the engine, whereas superchargers are driven by a geartrain or belt connected to the crankshaft of the engine.


Comparison

Strengths and weaknesses vary according to the method of forcing induction largely based upon the inherent design functions of both. A turbocharger acts as an obstacle to exhaust gases due to its placement in the exhaust system tract. A supercharger uses torque generated from the rotational mass internal to the engine through the crank pulley. A turbo relies on the volume and velocity of exhaust gases to spool, or spin the turbine wheel. The turbine wheel is connected to the compressor wheel via a common shaft. The compressor wheel compresses the intake charge increasing the charge density by a large factor. The amount of time that it takes a turbocharger to reach the onset of boost is referred to as lag. A supercharger is 'on' all of the time, meaning that it is capable of producing a linear increase of boost up until redline. It is easier to target a desired boost with a turbocharger as there are many forms of boost controllers that allow a user to adjust to desired boost fairly easily. In order to achieve desired boost with a supercharger, a larger or smaller pulley must be installed.


Intercooling

A fundamental principle to forced induction is that compressing air raises its temperature. As a result, the charge density is reduced and the cylinders receive less fresh air than the system’s boost pressure prescribes. The risk of pre-ignition or "knock" in internal combustion engines greatly increases. These drawbacks are countered by charge-air cooling, which passes the air leaving the turbocharger or supercharger through a heat exchanger typically called an intercooler. This is done by cooling the charge air with an ambient flow of either air (air-air intercoolers) or liquid (liquid to air intercoolers), the charge air density is increased and the temperature is reduced.


Alcohol/Water Injection

Additionally, alcohol injection is an effective means of cooling the charge air. Methanol is the preferred alcohol due to its elemental properties, and is normally mixed with water to prevent evaporation. Methanol is typically injected pre throttle body. Methanol, unlike nitrous oxide or forced induction itself, doesn't add more oxygen to the charge, but by its low evaporation point changes from a liquid to a gas as its introduced into the air charge. The evaporation process uses the heat from the intake charge to complete the phase change. The alcohol is also a fuel in the charge which will cause a rich condition if used in excess. Due to the lower intake temperatures and denser air charge more power is exerted from the engine. Methanol is typically used in conjunction with poor quality fuel(pump gas) in order to run higher than normal boost pressures.

Like was stated above, adding forced induction increases the amount of air an engine can use for combustion, in effect allowing more fuel to be used with the available oxygen. Further, it increases an engine's dynamic compression ratio. As compression ratio increases, so does the threat of knock and therefore the need for higher octane fuel.

Motronic

Bosch Motronic was one of the first digital engine-management systems. The idea behind it was to fully integrate and regulate all major engine system parameters, thereby enabling fuel delivery and spark timing control functions to be controlled by the same unit, in an attempt to achieve optimum efficiency, driveability and power output potential.

The early Motronic systems integrated spark timing control with existing Jetronic fuel injection systems, such as L-Jetronic, LH-Jetronic, K-Jetronic, and in some cases Mono-Jetronic. It was originally developed and first used in the BMW 7 Series, before being implemented on several Volvo and Porsche engines throughout the 1980s.

The components of the Motronic 1.x systems for the most part remained unchanged during production, although there are some differences in certain situations. The electronic control unit (ECU) receives information regarding engine speed and position, crankshaft angle, coolant temperature and throttle position.

An air flow meter is used to measure the volume of air entering the induction system, and a charge air temperature sensor monitors the temperature of the inducted air after it has passed through the turbocharger and the intercooler, in order to accurately calculate the overall air mass.

A separate constant idle speed (CIS) system monitors and regulates base idle speed, depending if an interior electrical component is in operation. A cold start (5th) injector is used to provide extra fuel enrichment during different cold-start conditions.

1. ^ 25 years of Bosch Motronic: Think tank under the bonnet, Bosch, may 2004

Napier Nomad engine (aircraft engine)

The Nomad was a complex Diesel cycle aircraft engine from Napier & Son of the UK. The Nomad used a turbine to recover power from the exhaust of the otherwise conventional Diesel engine, resulting in a specific fuel consumption that remains unmatched by an aircraft engine 50 years later.


History

In 1945 the Air Ministry asked for proposals for a new 6,000 horsepower (4,500 kW) class engine with good economy. Curtiss-Wright was designing an engine of this sort of power known as the "turbo-compound", but Sir Harry Ricardo, one of Britain's great engine designers, suggested that the most economical combination would be a similar design using a diesel two-stroke in place of the Curtiss's petrol engine.

Prior to World War II Napier had licensed the Junkers Jumo 204 diesel design to set up production in the UK as the Napier Culverin, however the start of the war made the Sabre all-important and work on the Culverin was stopped. In response to the Air Ministry requirements they dusted off this work, combining two enlarged Culverins into an H-block similar to the Sabre, resulting in a massive 75 litre design. Markets for an engine of this size seem limited however, and instead they returned to the original Culverin-like horizontally opposed 12 cylinder design, resulting in the Nomad.

Design

The Nomad design was incredibly complex, essentially two engines in one. One was a supercharged Diesel similar to the Culverin. Below this was a complete turboprop engine, based on their Naiad design. The output of the turboprop was geared to a shaft running inside the Diesel's, driving the front propeller of a contra-rotating pair. As if that were not enough, during takeoff additional fuel was dumped into the rear turbine stage for additional power, and turned off once the plane was cruising.

The compressor and turbine assemblies of the Nomad 1 were tested during 1948, and the complete unit was run in October 1949. The prototype was installed in the nose of an Avro Lincoln bomber for testing, and first flew in 1950. In total the Nomad 1 ran for just over 1,000 hours, and proved to be rather temperamental, but when running properly it could produce 3000 hp (2,200 kW) and 320 lbf (1.4 kN) thrust. It had a specific fuel consumption (sfc) of 0.36 lb/(hp·h) (0.22 kg/(kW·h)).

Even before the Nomad 1 was running, its replacement, the Nomad 2, had already been designed. In this version an extra compressor stage was added, replacing the original supercharger. This stage was driven by an additional stage in the turbine, so the system was now more like a turbocharger and the compressed air for the Diesel was no longer "robbing" power. In addition the propeller shaft from the turbine was eliminated, and geared using a hydraulic clutch into the main shaft. The result was smaller and considerably simpler, a single engine driving a single propeller.

While the Nomad 2 was undergoing testing, a prototype Avro Shackleton was lent to Napier as a testbed. The engine proved bulky, like the Nomad 1 before it, and in the meantime several dummy engines were used on the Shackleton for various tests. By 1954 interest in the Nomad was dropping, and after the only other project based on it was cancelled, work on the engine was ended in April 1955.


Specifications (Nomad 2)

General characteristics

* Type: Twelve-cylinder liquid-cooled horizontally opposed Diesel combined with a turboprop aircraft engine
* Bore: 6 in (152 mm)
* Stroke: 7.375 in (187 mm)
* Displacement: 2,502 in³ (41 L)
* Dry weight: 3,580 lb (1,624 kg)

Components

* Cooling system: Liquid-cooled

Performance

* Power output: 3,135 ehp (2,338 kW) max take-off at 89 psia (614 kPa) including thrust power from the turbine
* Specific power: 1.25 ehp/in³ (57.0 kW/L)
* Compression ratio:
o Engine 8:1
o Turboprop compressor 8.25:1
* Specific fuel consumption: 0.345 lb/(ehp·h) (0.210 kg/(kW·h))
* Power-to-weight ratio: 0.88 ehp/lb (1.44 kW/kg)

Wright R-3350 engine

The R-3350 Duplex-Cyclone was one of the most powerful radial aircraft engines produced in the United States. It was a twin row, supercharged, air-cooled, radial engine with 18 cylinders. Power ranged from 2,200 to over 3,700 hp (1,640 to 2,760 kW), depending on the model. First developed prior to World War II, the R-3350's design required a long time to mature before finally being used to power the B-29 Superfortress. After the war, the engine had matured sufficiently to become a major civilian airliner design, notably in its Turbo-Compound forms.

In 1927 Wright Aeronautical introduced their famous Cyclone engine, which powered a number of designs in the 1930s. After merging with Curtiss to become Curtiss-Wright in 1929, an effort was started to redesign the engine to the 1,000 hp (750 kW) class. The new Wright R-1820 Cyclone 9 first ran successfully in 1935, and would become one of the most-used aircraft engines in the 1930s and WWII.

At about the same time Pratt & Whitney had started a development of their equally famous Wasp design into a larger and much more powerful two-row design that would easily compete with this larger Cyclone. In 1935 Wright decided to follow P&W's lead, and started to develop much larger engines based on the mechanicals of the Cyclone. The result were two designs with a somewhat shorter stroke, a 14 cylinder design that would evolve into the Wright R-2600, and a much larger 18 cylinder design that became the R-3350.

The first R-3350 was run in May 1937, but proved to be rather temperamental. Continued development was slow, both due to the complex nature of the engine, as well as the R-2600 receiving considerably more attention. The R-3350 didn't fly until 1941, after the prototype Douglas XB-19 had been re-designed from the Allison V-3420 to the R-3350.

Things changed dramatically in 1940 with the introduction of a new contract by the USAAC to develop a long-range bomber capable of flying from the US to Germany with a 2,000 lb (900 kg) bomb load. Although smaller than the Bomber D designs that led to the B-19, the new designs required roughly the same sort of power. When preliminary designs were returned in the summer of 1940, three of the four designs were based on the R-3350. Suddenly the engine was seen as the future of Army aviation, and serious efforts to get the design into production started.

By 1943 the ultimate development of the new bomber program, the B-29, was flying. However the engines remained temperamental, and showed an alarming tendency to overheat. A number of changes were introduced into the aircraft production line in order to provide more cooling at low speeds, and the planes were rushed to operate in the Pacific in 1944. This proved unwise, as the overheating problems were not completely solved, and the engines had a tendency to burst into flame after takeoff.

Early versions of the R-3350 were equipped with carburetors, which led to serious problems with inadequate fuel mixture distribution. Near the end of World War II, in late 1944, the system was changed to use direct fuel injection, where fuel was injected directly into the combustion chamber. This change improved engine reliability immediately. After the war the engine became a favourite of large aircraft of all designs, most notably the Lockheed Constellation and Douglas DC-7.

Following the war, in order to better serve the civilian market, the Turbo-Compound system was developed in order to deliver better "gas milage". In these versions of the engine, three separate power recovery turbines were attached to the exhaust piping of each group of 6 cylinders, using the power not to deliver additional boost as in a normal turbocharger, but geared directly to the engine crankshaft by fluid drives in order to deliver more power. This recovered about 20% of the heat of the exhaust, (something around 500 hp) which would otherwise be wasted. This is not without cost, however, for those devices are also nicknamed "Parts Recovery Turbines" (and worse), and were another source of failures.

By this point reliability had improved, with the mean time between overhauls at 3,500 hours, and specific fuel consumption on the order of 0.4 lb/hp.hour (243 g/kWh). Engines still in use are now limited to 52 inches of manifold pressure and 2,880 HP with 100 octane fuel (100LL) instead of the 59.5 inches and 3,400 HP possible with 115/145 fuels, which are no longer available.

Maserati Quattroporte

Vehicle Overview
Changes for Maserati's 2007 Quattroporte include suspension modifications intended to soften the car's ride, a stronger climate control system, stronger brakes and reduced emissions courtesy of an updated catalytic converter. Inside, the steering wheel and handbrake stitching no longer contrasts with the surrounding leather, and folding tables for backseat passengers are no longer available.

For the 2005 model year, Maserati introduced a full-size four-door luxury sedan called the Quattroporte. Designed by Pininfarina, the rear-wheel-drive Quattroporte competes against the Audi A8, BMW 7 Series and Mercedes-Benz S-Class.

The Quattroporte has Brembo all-disc brakes and a Skyhook automatic-damping suspension. A V-8 engine works with Maserati's DuoSelect sequential transmission, which can be shifted using paddles mounted on the steering column. Maserati says the Quattroporte can accelerate from zero to 60 mph in a swift 5.2 seconds. For optimum weight distribution, the engine sits aft of the front axle and drives a rear-mounted transmission.

Two versions of the Quattroporte arrived in late 2005: an Executive GT and a Sport GT. The Executive GT has polished 19-inch wheels and heated, ventilated and massaging rear seats. A wood and leather steering wheel also is installed.

The Sport GT features 20-inch wheels, carbon fiber trim, racing pedals, and a black grille and side air vents. Maserati's Skyhook suspension system has been modified for use in the Sport GT, and the car has a sport exhaust system.

Exterior
Recognizable Maserati styling cues include its long hood, prominent grille and headlights. Low-slung front fenders, short front overhangs, a swept-back profile, a high belt line and a steeply raked windshield also help establish what the company calls an "authoritative persona [and] predatory appearance."

A broad horizontal-bar grille contains Maserati's Trident badge. The headlights sit slightly back, and a wide air intake is installed below the grille. Three portholes adorn each front fender. Standard wheels measure 18 inches in diameter. Built on a relatively long 120.6-inch wheelbase, the Quattroporte is 198.9 inches long overall and 56.6 inches tall.

Interior
Five people can luxuriate inside the Quattroporte, where handcrafted leather complements the premium wood trim. Rosewood is standard, but buyers can specify mahogany, burl walnut, a titanium-style trim or piano black finish.

Standard features include power front and rear seats, a power rear sunshade and a cooled compartment in the front armrest. Touching a button in the center rear armrest moves the front passenger seat forward, supplying additional legroom. The Bosch-Blaupunkt Multi Media System includes a navigation system, Bose stereo and TV tuner.

Under the Hood
The Quattroporte's 4.2-liter V-8 engine generates close to 400 horsepower and 333 pounds-feet of torque. The six-speed sequential transmission can be shifted using paddles mounted on the steering column, but it also includes a fully automatic mode. A Low Grip mode is included for driving in poor weather.

Safety
All-disc antilock brakes, an electronic stability system, side-impact airbags for the front seats and side curtain airbags are standard.

Rear disc brakes are larger for 2007 — growing from 12.4 to 13 inches. Maserati says this reduces the Quattroporte's stopping distance from 62 mph by 5 percent.

Whats a Stationary engine

A stationary engine is an engine whose framework does not move. It is normally used not to propel a vehicle but to drive a piece of immobile equipment such as a pump or power tool.

This article concentrates on oil-burning or internal combustion engines;
steam-powered engines are described separately in stationary steam engine.


Overview

Stationary engines come in a wide variety of sizes and use a wide variety of technologies. These include:

* Power stations of all sizes.

* Beam engines used in mills and factories before the widespread use of electric power.

* Winding engines used at mine pitheads.


Railways

In Victorian era railway engineering, many attempts were made to replace locomotives by stationary engines, on the grounds that it was inefficient to move something as large and heavy as a steam engine around. These attempts only succeeded where short distances were to be covered, where various kinds of cable railway were successful, particularly for steep inclines (where the inefficiency of moving the engine up and down a hill is particularly significant). A heroic failure was Isambard Kingdom Brunel's attempt to construct an atmospheric railway from Exeter to Plymouth in Devon, England.

Cable haulage did prove viable where the gradients were exceptionally steep, such as the 1 in 8 gradients of the Cromford and High Peak Railway opened in 1830. Cable railways generally have two tracks with loaded wagons on one track partially balanced by empty wagons on the other, to minimise fuel costs for the stationary engine.


Farms

Small stationary engines were frequently used on a farm to drive various kinds of power tools and equipment such as circular saws, pumps, and hay elevators. The engine was fitted to a wooden trolley with steel wheels so that it could be moved to where required, and was then coupled to the equipment by means of a flat belt.

The engines were usually powered by gasoline, but in some cases for economy it was possible to switch over to run on paraffin after the engine had warmed up - to achieve this required a part of the inlet tract to be heated by exhaust gases in order to vaporise the less volatile fuel. Very large stationary engines ran on a heavier type of fuel oil, but this type of engine was usually too large to be moved; typical applications were electricity generation and large-scale pumping.

Initially, such engines mirrored steam engine design in having the piston move horizontally, with the crank and valve gear exposed and employed a drip-feed total loss lubrication system. Later for safety, cleanliness and longevity the design moved towards enclosing the working parts and using sump lubrication.

The four-stroke cycle design was by far the most common, but Petter, a British manufacturer, developed a successful two-stroke cycle design.

A centripetal governor system was usually incorporated to regulate the engine's speed under varying loads. This is a simple negative feedback control system. The engine speed is sensed by a pair of weights that rotate with the crankshaft. As the speed increases, centripetal force causes the weights to move outward against the pressure of a retaining spring. This outward movement is used to restrict the engine power to limit the speed. If the engine slows down, the centrifugal force reduces and the weights are pulled inward by spring pressure, and this movement is used to increase the engine power to maintain speed under increasing load.

The governor can use one of two techniques for controlling speed. Today, most governors open and close a butterfly valve to control the amount of fuel-air mixture entering the engine. However, in earlier engines, the governor would cut off the fuel air mixture completely. These engines are often called "hit and miss" (variously called "hit or miss") because they do not fire on every available power stroke. When the engine is running above a certain rpm, the exhaust valve is held open, and the magneto is prevented from generating a spark. Once the speed drops, the governor allows the exhaust valve to close and the magneto to fire. The engine fires and speeds back up, causing the governor to keep the exhaust valve open again.

On a medium size engine such as a 6hp, the engine can be adjusted so that it only fires every 10 seconds or so when it is not under load. These engines generally drove a wide flat belt to run a firewood cutoff saw, a pump, a reciprocating log saw, etc.

Eventually such engines were rendered obsolete by the development of electrically powered tools, and by newer gasoline engines that were small and economical enough to be permanently built in to each piece of equipment.

Live steam models of stationary engines are popular among collectors and hobbyists.

Harmonic balancer

A harmonic balancer (also called crank pulley damper, torsional damper or vibration damper) is a device connected to the crankshaft of an engine to reduce torsional vibration.

Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.

To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations.

Over time, the energy dissipating (rubber/clutch/fluid) element can deteriorate from age, heat, cold, or exposure to oil or chemicals. Unless rebuilt or replaced, this can cause the crankshaft to develop cracks, resulting in crankshaft failure.

There has been a trend at times by some "performance enthusiasts" to remove the harmonic balancers on their cars. The argument is that they aren't necessary and their mass reduces the performance of the engine. Others argue that this is not worth it, because the danger of damage to the engine from the vibrations the damper is intended to prevent is too high.

While net engine output can be increased without harmonic balancers, in professional race cars harmonic balancers are still commonly equipped, for reasons ranging from safety concerns to regulations. Almost all modern car manufacturers, even "performance" car makers and specialty tuners, include a harmonic balancer on their vehicles, and removal voids vehicle warranty.

Reverse-flow cylinder head

A reverse-flow cylinder head is a cylinder head that locates the intake and exhaust ports on the same side of the engine. The gasses can be thought to enter the cylinder-head and then change direction in order to exit the head. This is in contrast to the cross-flow cylinder-head design. This term is used for engines which have only one intake and one exhaust valve per cylinder.

The reverse-flow design is accepted to be inferior to a cross-flow design in terms of ultimate engineering potential, however, the reverse-flow design has been shown to be a more practical and economical manufacturing proposition and has similar potential in forced induction applications (where overly-large valves and "through flow" of gasses on cam overlap are not as desirable as under normally-aspirated conditions).

The real problem is that of temperature. With the exhaust ports on the same side as the intake ports, the intake air gets some of the heat, which reduces efficiency.

Why buy a Hybrid Car

1. - Gas Savings -
Hybrid cars can get up to 60 mpg (miles per gallon), due to their advanced aerodynamics, engine efficiency, tire technology (which is so different to the standard cars) just to mention some of its characteristics.

2. - Environmental Issues -
Reduced gas emissions equals less air pollution because a hybrid car has an electric motor and batteries to rely on when the gasoline engine is not in use. They can reduce smog up to 90%.

3. - Better engine efficiency -
Reducing the overall weight of the hybrid car is a way to increase its efficiency, smaller engines equals better efficiency. Another way is how the hybrid cars recharge they batteries, the hybrids battery pack never needs to be charged from an external source, every time you hit the brake, the brake system stores some of the energy to the batteries (this is known as regenerative braking). Also the batteries get recharged by the gasoline engine when necessary.

4. - Low Maintenance costs -
The electrical motor and the batteries dont require any maintenance; they have the same life span as the car itself. The gas engine doesnt require any more maintenance than any other normal car.

Autogas

Autogas is the common name for liquified petroleum gas when it is used as a fuel in internal combustion engines in vehicles. The same equipment is also used for similar engines in stationary applications such as generators.

Autogas is widely used as a "green" fuel as it decreases exhaust emissions (less 20 % CO2) . It has an octane rating (MON/RON) that is between 90 and 110 and an energy content (higher heating value—HHV) that is between 25.5 megajoules per litre (for pure propane) and 28.7 megajoules per litre (for pure butane.)

In countries where petrol is called petrol rather than gasoline, it is common for autogas to be simply referred to as gas. This can be confusing for people from countries where petrol is called gasoline, as they often use the abbreviation gas to refer to petrol. In the United States, autogas is more commonly known under the name of its primary constituent, propane.


Vehicle manufacturers

Toyota made a number of LPG engines in their 1970s M, R, and Y engine families.

Currently, a number of automobile manufacturers—Citroën, Fiat, Ford, Hyundai, General Motors (including Daewoo, Holden, Opel/Vauxhall, Saab), Peugeot, Renault, Toyota and Volvo—have OEM bi-fuel (dual fuel) models that will run equally well on both LPG and petrol. See list of LPG cars.

Vialli have OEM LPG powered scooters and LPG powered mopeds that run equally well on LPG. Ford Australia have offered an LPG-only variant of their Falcon model since 2000.

MAN AG produces LPG buses.

Countries

Autogas enjoys great popularity in Australia, The Netherlands, Italy, Serbia, Poland, Hong Kong and Korea. The former Soviet republic of Armenia may, however, be the world leader in autogas use. The Armenian transport ministry estimates as much as 20 to 30% of vehicles use autogas compared to traditional gasoline, once again due to the fact that it offers a very cheap alternative to both diesel and petrol, being less than half the price of petrol and some 40% cheaper than diesel. The recent rises in oil-derived fuels has sharply raised the difference.


Europe

The european standard is EN 589


Australia

LPG is popular in Australia, in part due to it being less than half the price of petrol in urban areas. The four major local manufacturers (Ford, Holden, Mitsubishi and Toyota) offer it in some models of their locally made large cars. All factory autogas vehicles are dual fuel vehicles, with the exception of the E-Gas Ford Falcon model, which runs on autogas only.

Autogas is especially popular with taxis, except in remote areas where transportation costs make autogas prices uncompetitive.

Whilst LPG is currently excise-free, an excise on LPG starting at 2.5 cents per litre in 2011 will be placed, which will increase incrementally to 12.5 cents per litre (as opposed to the 38 cpl excise on petrol) by 2015. This will be offset somewhat by a AU$2000 subsidy that was implemented in 2006 for private motorists to convert their cars to LPG.The subsidy does not presently apply to business vehicles or vehicles with a Gross Vehicle Mass of over 3500 kilograms but lobbyists are trying to get that changed. On top of the subsidy to be provided by the Australian federal government, the Western Australian government will also provide motorists with a AU$1000 subsidy under the long-running LPG subsidy scheme.


System types

The different autogas systems generally use the same type of filler, tanks, lines and fittings but use different components in the engine bay. Some injection systems use special tanks with circulation pumps and return lines similar to petrol fuel injection systems.

There are three basic types of autogas system. The oldest of these is the conventional converter-and-mixer system, which has existed since the 1940s and is still widely used today. The other two types are known as injection systems, but there are significant differences between the two.

A converter-mixer system uses a converter to change liquid fuel from the tank into vapour, then feeds that vapour to the mixer where it is mixed with the intake air.

Vapour phase injection systems use a converter in much the same way as with a mixer, but have a series of electrical shutoff solenoids and nozzles (collectively referred to as injectors) that are controlled by a computer. The computer works in much the same way as a petrol fuel injection computer. This allows much more accurate metering of fuel to the engine than is possible with mixers, improving economy and/or power while reducing emissions.

Liquid phase injection systems do not use a converter, but instead deliver the liquid fuel into a fuel rail in much the same manner as a petrol injection system. These systems are still very much in their infancy. Because the fuel vapourises in the intake, the air around it is cooled significantly. This increases the density of the intake air and can potentially lead to substantial increases in engine power output, to the extent that such systems are usually de-tuned to avoid damaging other parts of the engine. Liquid phase injection has the potential to achieve much better economy and power plus lower emission levels than are possible using mixers or vapour phase injectors.


System components

Filler

The fuel is transferred into a vehicle tank as liquid by connecting the bowser at the filling station to the filler fitting on the vehicle.

The type of filler used varies from country to country:

* The type used in Australia and the USA has an ACME threaded fitting onto which the bowser nozzle is screwed before the trigger is pulled to establish a seal then transfer fuel.
* The type used in other countries is the Bajonett.

The fill valve contains a check valve so that the liquid in the line between the filler and the tank(s) does not escape when the bowser nozzle is disconnected.

In installations where more than one tank is fitted, T-fittings may be used to connect the tanks to one filler so that the tanks are filled simultaneously. In some applications, more than one filler may be fitted, such as on opposite sides of the vehicle. These may be connected to separate tanks, or may be connected to the same tanks using T-fittings in the same manner as for connecting multiple tanks to one filler.


Hoses, pipes and fittings

The hose between the filler and tank(s) is called the fill hose or fill line. The hose or pipe between the tank(s) and the converter is called the service line. These both carry liquid under pressure.

The flexible hose between the converter and mixer is called the vapour hose or vapour line. This line carries vapour at low pressure and has a much larger diameter to suit.

Where the tank valves are located inside an enclosed space such as the boot of a sedan, a plastic containment hose is used to provide a gas-tight seal between the gas components and the inside of the vehicle.

Liquid hoses for LPG are specifically designed and rated for the pressures that exist in LPG systems, and are made from materials designed to be compatible with the fuel. Some hoses are made with crimped fittings, while others are made using re-usable fittings that are pressed or screwed onto the end of the hose.

Rigid sections of liquid line are usually made using copper tubing, although in some applications, steel pipes are used instead. The ends of the pipes are always double-flared and fitted with flare nuts to secure them to the fittings.

Liquid line fittings are mostly made from brass. The fittings typically adapt from a thread in a component, such as a BSP or NPT threaded hole on a tank, to an SAE flare fitting to suit the ends of pipes or hoses.


Tank

Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications.

The tanks have fittings for filling, liquid outlet, emergency relief of excess pressure, fuel level gauge and sometimes a vapour outlet. These may be separate valves mounted into a series of 3 to 5 holes in a plate welded into the tank shell, or may be assembled onto a multi-valve unit which is bolted into one large hole on a boss welded into the tank shell.

Modern fill valves are usually fitted with an automatic fill limiter (AFL) to prevent overfilling. The AFL has a float arm which restricts the flow significantly but does not shut it off entirely. This is intended to cause the pressure in the line to rise enough to tell the bowser to stop pumping but not cause dangerously high pressures. Before AFLs were introduced, it was common for the filler (with integral check valve) to be screwed directly into the tank, as the operator had to open an ullage valve at the tank while filling, allowing vapour out of the top of the tank and stopping filling when liquid started coming out of the ullage valve to indicate that the tank was full. Modern tanks are not fitted with ullage valves.

The liquid outlet is usually used to supply fuel to the engine, and is usually referred to as the service valve. Modern service valves incorporate an electric shutoff solenoid. In applications using very small engines such as small generators, vapour may be withdrawn from the top of the tank instead of liquid from the bottom of the tank.

The emergency pressure relief valve in the tank is called a hydrostatic pressure relief valve. It is designed to open if the pressure in the tank is dangerously high, thus releasing some vapour to the atmosphere to reduce the pressure in the tank. The release of a small quantity of vapour reduces the pressure in the tank, which causes some of the liquid in the tank to vapourise to re-establish equilibrium between liquid and vapour. The latent heat of vapourisation causes the tank to cool, which reduces pressure even further.

The gauge sender is usually a magnetically coupled arrangement, with a float arm inside the tank rotating a magnet, which rotates an external gauge. The external gauge is usually readable directly, and most also incorporate an electronic sender to operate a fuel gauge on the dashboard.



Valves

There are a number of types of valve used in autogas systems. The most common ones are shutoff or filterlock valves, which are used to stop flow in the service line. These may be operated by vacuum or electricity. On dual-fuel systems with a petrol carburettor, a similar shutoff valve is usually fitted in the petrol line between the pump and carburettor.

Check valves are fitted in the filler and on the fill input to the fuel tank to prevent fuel flowing back the wrong way.

Service valves are fitted to the outlet from the tank to the service line. These have a tap to turn the fuel on and off. The tap is usually only closed when the tank is being worked on. In some countries, an electrical shutoff valve is built into the service valve.

Where multiple tanks are fitted, a combination of check valves and a hydrostatic relief valve are usually installed to prevent fuel from flowing from one tank to another. In Australia, there is a common assembly designed for this purpose. It is a combined twin check valve and hydrostatic relief valve assembly built in the form of a T-fitting, such that the lines from the tanks come into the sides of the valve and the outlet to the converter comes out the end. Because there is only one common brand of these valves, they are known colloquially as a Sherwood valve.


Converter

The converter (also known as vapouriser) is a device designed to change the fuel from a pressurised liquid to a vapour at around atmospheric pressure for delivery to the mixer or vapour phase injectors. Because of the refrigerant characteristic of the fuel, heat must be put into the fuel by the converter. This is usually achieved by having engine coolant circulated through a heat exchanger that transfers heat from that coolant to the LPG.

There are two distinctly different basic types of converter for use with mixer type systems. The European style of converter is a more complex device that incorporates an idle circuit and is designed to be used with a simple fixed venturi mixer. The American style of converter is a simpler design which is intended to be used with a variable venturi mixer that incorporates an idle circuit.

Engines with a low power output such as; scooters, quad bikes and generators can use a simpler type of convertor (also known as governor or regulator). These convertors are fed with fuel in vapour form. Evaporation takes place in the tank where refrigeration occours as the liquid fuel boils. The tanks large surface area exposed to the ambient air temperature combined with the low power output (fuel requirment) of the engine make this type of system viable. The refrigeration of the fuel tank is proportional to fuel demand hence this setup is only used on smaller engines. This type of convertor can either fed with vapour at tank pressure (called a 2 stage regulator) or be fed via a tank mounted reguator at a fixed reduced pressure(called a single stage regulator).


Mixer

The mixer is the device that mixes the fuel into the air flowing to the engine. The mixer incorporates a venturi designed to draw the fuel into the airflow due to the movement of the air.

Mixer type systems have existed since the 1940s and some designs have changed little over that time. Mixers are now being increasingly superceeded by injectors.


Vapour phase injectors

Most vapour phase injection systems mount the solenoids in a manifold block or injector rail, then run hoses to the nozzles, which are screwed into holes drilled and tapped into the runners of the intake manifold. There is usually one nozzle for each cylinder. Some vapour injection systems resemble petrol injection, having separate injectors that fit into the manifold or head in the same manner as petrol injectors, and are fed fuel through a fuel rail.


Liquid phase injectors

Liquid phase injectors are mounted onto the engine in a manner similar to petrol injectors, being mounted directly at the inlet manifold and fed liquid fuel from a fuel rail.


Electrical and electronic controls

The are four distinct electrical systems that may be used in autogas systems - fuel gauge sender, fuel shutoff, closed loop feedback mixture control and injection control.

In some installations, the fuel gauge sender fitted to the autogas tank is matched to the original fuel gauge in the vehicle. In others, an additional gauge is added to display the level of fuel in the autogas tank separately from the existing petrol gauge.

In most modern installations, an electronic device called a tachometric relay or safety switch is used to operate electrical shutoff solenoids. These work by sensing that the engine is running by detecting ignition pulses. Some systems use an engine oil pressure sensor instead. In all installations, there is a filterlock (consisting of a filter assembly and a vacuum or electric solenoid operated shutoff valve) located at the input to the converter. In European converters, there is also a solenoid in the converter to shut off the idle circuit. These valves are usually both connected to the output of the tachometric relay or oil pressure switch. Where solenoids are fitted to the outputs of fuel tanks, these are also connected to the output of the tachometric relay or oil pressure switch. In installations with multiple tanks, a switch or changeover relay may be fitted to allow the driver to select which tank to use fuel from. On dual-fuel systems, the switch used to change between fuels is used to turn off the tachometric relay.

Closed loop feedback systems use an electronic controller that operates in much the same way as in a petrol fuel injection systems, using an oxygen sensor to effectively measure the air/fuel mixture by measuring the oxygen content of the exhaust and control valve on the converter or in the vapour line to adjust the mixture. Mixer type systems that do not have a closed loop feedback fitted are sometimes referred to as open loop systems.

Injection systems use a computerised control system which is very similar to that used in petrol injection systems. In virtually all systems, the injection control system integrates the tachometric relay and closed loop feedback functions.


Converter-and-mixer system operation

The designs of converters and mixers are matched to each other by matching sizes and shapes of components within the two.

In European style systems, the size and shape of the venturi is designed to match the converter. In American style systems, the air valve and metering pins in the mixer are sized to match the diaphragm sizes and spring stiffnesses in the converter. In both cases, the components are matched by the manufacturers and only basic adjustments are needed during installation and tuning.

An autogas carburettor simply consists of a throttlebody and a mixer, sometimes fitted together using an adapter.

Cold start enrichment is achieved by the fact that the engine coolant is cold when the engine is cold. This causes denser vapour to be delivered to the mixer. As the engine warms up, the coolant temperature rises until the engine is at operating temperature and the mixture has leaned off to the normal running mixture. Depending on the system, the throttle may need to be held open further when the engine is cold in the same manner as with a petrol carburetor. On others, the normal mixture is intended to be somewhat lean and no cold-start throttle increase is needed. Because of the way enrichment is achieved, no additional choke butterfly is required for cold starting with LPG.

The temperature of the engine is critical to the tuning of an autogas system. The engine thermostat effectively controls the temperature of the converter, thus directly affecting the mixture. A faulty thermostat, or a thermostat of the wrong temperature range for the design of the system may not operate correctly.

The power output capacity of a system is limited by the ability of the converter to deliver a stable flow of vapour. A coolant temperature lower than intended will reduce the maximum power output possible, as will an air bubble trapped in the cooling circuit or complete loss of coolant. All converters have a limit, beyond which mixtures become unstable. Unstable mixtures typically contain tiny droplets of liquid fuel that were not heated enough in the converter and will vapourise in the mixer or intake to form an excessively rich mixture. When this occurs, the mixture will become so rich that the engine will flood and stall. Because the outside of the converter will be at or below zero degrees Celsius when this happens, water vapour from the air will freeze onto the outside of the converter, forming an icy white layer. Some converters are very suceptible to cracking when this happens.


Performance

The Yellow-Checker-Star taxi fleet of Las Vegas, NV is a well known propane user. These taxis are mostly production gasoline Crown Victoria conversions. When the larger propane fuel tank replaces the smaller gasoline tank, about 1/8 of the trunk space is lost. Maximum distance varies between 250 to 320 miles on one full tank. Fuel capacity varies a great deal with ambient temperature. In the coldest desert winter nights taxis might travel up to 400 miles or more. But in the hotest summer days taxis might achieve only 180 miles. When it is very hot, refueling requires extra time. This can cause long lines to form at refueling stations, particularly during shift changes.

It's a common rule of thumb in Australia that a dual fuel car will use about 20-30% more fuel than an equivalent petrol car, and has about 20-30% less power. Modern injection systems are making the gap smaller, however, as do dedicated LPG systems, since they don't have to be able to run both LPG and petrol.


LPG injection for diesel vehicles

The performance, economy and emission profile of diesel engines can be improved by injecting a small quantity of LPG into the inlet manifold. It is claimed that the LPG increases the burning efficiency of the diesel fuel from typically 75-85%, to 95-98%.

The systems typically operate by metering a small quantity of LPG, at a pressure slightly above atmospheric, into the intake manifold, where it enters the combustion chamber and is ignited with the diesel. LPG flow is regulated to ensure smooth operation, and will typically only deliver LPG under power.

Some companies claim a 10% to 20% increase in power and torque, and a reduction in overall fuel costs. Any actual savings are dependent on the relative cost of diesel versus LPG. In Australia, where diesel costs substantially more then LPG, savings of 10 to 20% are claimed.

Automotive Accessories : Spark Plug Voltage Stabilizer

* for Petrol/Gasoline vehicles

The spark [at the spark plug] is fundamental to cause ignition and thus combustion of the Air/Fuel mixture.

Spark at the spark plug is created by a high voltage that comes from the ignition coil.

The +12 Volt car battery is the main power source to many users of a vehicle; i.e.

* air conditioner
* head-lights
* wipers
* hi-fi and radio
* other electrical items, etc

As such, consistent supply cannot be guaranteed to the ignition coil via the +12 Volt Car Battery. When this happens, the spark may be too small to cause burning of the Air/Fuel mixture, or mis-firing, causing 100% unburn fuel to be released to the environment through the exhaust system.

This is also true when the vehicle is running at high rpm, and sparkings has to take place in shorter interval. So, when the car battery is not able to consistently supply the same power to the ignition coil, smaller or no sparking will occur.


Concept of Work

The Spark Plug Voltage Stabilizer is installed at the front of the ignition coil(s).

The Spark Plug Voltage Stabilizer concept of work is to take residual energy from the car and make it into good use. It relies less of the car battery in supplying the require power to the ignition coil. Revolutionary circuit design allows more Sparks.And this is achieved through a much higher Voltage delivery to the spark plugs.

* Impact of Optimized sparks
o Reducing unburn fuel will improve Fuel Consumption; because of less wastage [unburn fuel].
o The result of better burning improves car response, increasing power to the vehicle.


Types of Ignition Coils

The Spark Plug Voltage Stabilizer works on all different types of Ignition Coil Designs.

Earlier car design has the ignition coil as a separate unit. It is then connected to a 'distributor unit' which will sequence the high voltage generated to the respective spark plug.

Current design for single ignition coil system is called the 'Built-In Coil'. This houses both the Ignition Coil and Distributor as one unit.

* Single Coil - works with a separate Distributor unit
* Built-In Coil - Ignition Coil and Distributor unit in one
* Multi Coil; may be
o 2 Ignition coils
+ 1 Ignition coil to 2 spark plugs, or
+ 1 Ignition coil to 3 spark plugs [V6 engine]
o 3 coils
+ 1 Ignition coil to 1 spark plug, [3 cylinders engine eg. Perodua [Malaysia] or
+ 1 Ignition coil to 2 spark plugs [V6 engine]
o 4 coils
+ 1 Ignition coil to 1 spark plug [DIS - Direct Ignition Coil System, or Distributorles Ignition Coil System]
o More than 4 Coils, such as 6 coils (V6 engine), etc


Factors to better Fuel Consumption

There are many websites giving advice to improve fuel economy. Beside ensuring the vehicles at tip top conditions, the right foot is key! However, to attack the problem at the source; the Spark Plug Voltage Stabilizer has its merit.

Other products are available in the car accessories market to help in this area. Some of them, notably are :

*
o Voltage Stabilizer
o Magnet systems on the fuel line
o Fuel additives
o Cold Air Intake
o Special Air Filters
o Special Engine Oils
o Special Spark Plugs
o Highly Conductive Spark Plug Cables
o Your Right Foot, artificial or otherwise

*
o Latest product in the market : Patented composite material 'Titanium Ceramic' that influence the breaking up of clustered Air Molecules that allow easier combustion in the cylinder.

Cleaning a car engine

start the engine, let it warm up for a few minutes then shut it off, in order to soften up collected grease and grit in your engine compartment.

correct cleaning temperature for the engine to be is warm but not hot- you should be able to hold your hand to the engine without burning it.

Before cleaning the engine with water, it's imperative to cover electrical and mechanical components beneath the hood to protect them from water damage.

The air intake/air filter, the distributor, the coil and the oil dipstick/breather should be covered using plastic baggies sealed with rubber bands.

It's a good idea to also check the tightness of the
1) oil filler cap
2) power steering filler cap
3) windshield washer fluid cap
4) oil dip stick
5) battery filler caps


Spray all over the engine and engine compartment with non-petroleum based degreaser,

starting from
the bottom and working up.

Citrus degreasing products will not harm the paint or finish on aluminum components and are biodegradable.

After 3-5 minutes use a soft cotton towel or brush to carefully scrub the heavy dirt. Re-spray and re-scrub any areas that need additional cleaning.

Once the whole engine and engine compartment has been cleaned, rinse thoroughly with water.

Try to avoid getting the degreaser on any exterior painted areas as it will strip the wax from your finish. If this happens, it's okay, but you'll have to give those areas a good wax job when you're through.

Once clean, right away take off all the plastic baggies.

Dry any collected water, especially on aluminum parts, with a soft cotton towel.

Using paper towels, dry the battery.

Start the engine and let it warm up, in order to dry the remainder of the engine and evaporate any moisture in sensitive components. Once everything is dry and cooled off is a good chance to put a coating of rubber protectant on your rubber hoses, plastic shields and rubber gaskets.

If the battery terminals are dirty, disconnect the cables and clean both the cable terminals and battery posts with a wire brush.

Reconnect the terminals and retighten. Get some battery terminal spray and spray on the connected terminals to protect them from corrosion.

A thin coating of non-silicone lubricant should be applied to any hinges, throttle cables, cruise control cables and similar moving parts. Now check and top off fluid levels.

Key Engine Parts

key components inside an engine

Spark plug
The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.

Valves
The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.

Piston
A piston is a cylindrical piece of metal that moves up and down inside the cylinder.

Piston rings
Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

* They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.
* They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly.

Connecting rod
The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

Crankshaft
The crankshaft turns the piston's up and down motion into circular motion just like a crank on a jack-in-the-box does.

Sump
The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).

Operation and working cycle for Hot bulb engine

The hot-bulb engine shares its basic layout with nearly all other internal combustion engines, in that it has a piston inside a cylinder connected to a flywheel via a connecting rod and crankshaft. The flow of gases through the engine is controlled by valves. The majority operate on the standard 4-stroke cycle of an Induction Stroke, a Compression Stroke, a Power Stroke and an Exhaust Stroke.

The main feature of the hot-bulb engine is the vaporiser or hot-bulb, a chamber usually cast into the engine block and attached to the main cylinder by a narrow opening. Prior to starting the engine from cold, this vaporiser is heated externally by a blow-lamp or slow-burning wick (on later models sometimes electric heating or pyrotechnics was used) for as much as half an hour. The engine is then turned over, usually by hand but sometimes by compressed air or an electric motor.

Air is drawn into the cylinder through the intake valve as the piston descends (The Induction Stroke). During the same stroke, fuel is injected into the hot-bulb by a mechanical jerk-pump through a nozzle. Through the action of the injector and the heat of the hot-bulb, the fuel instantly vapourises. The air in the cylinder then forced through the top of the cylinder as the piston rises (The Compression Stroke), through the opening into the hot-bulb, where it is compressed and therefore its temperature rises. The vaporised fuel mixes with the compressed air and ignites due to the heat of the compressed air and the heat applied to the hot-bulb prior to starting. The fuel ignites, driving the piston down (The Power Stroke). The piston's action is converted to a rotary motion by the crankshaft which drives the flywheel, to which equipment can be attached for work to be performed. The flywheel also conserves momentum to turn the engine over the three strokes when power is not being produced. The piston rises again and the exhaust gases are expelled through the exhaust valve (The Exhaust Stroke). The cycle then starts again.

Once the engine is running, the heat of compression and ignition maintains the hot-bulb at the necessary temperature and the blow-lamp or other heat source can be removed. From this point the engine requires no external heat and requires only a supply of air, fuel oil and lubricating oil to run. The fact that the engine could be left unattended for long periods whilst running made hot bulb engines popular choices for powering generators and pumps.

Hot bulb engine Differences from the Diesel Engine

The hot-bulb engine is often confused with the diesel engine, and it is true that the two engines are very similar. Aside from the obvious lack of a hot-bulb vaporiser in the diesel engine, the main differences are that:

* The hot-bulb engine uses both compression-ignition and the heat retained in the vaporiser to ignite the fuel.

* The diesel engine uses just compression-ignition to ignite the fuel, and it operates at pressures many times higher than the hot-bulb engine.

Due to the much greater and longer-term success of the diesel engine, today hot-bulb engines are sometimes called 'semi-diesels' or 'semi diesel' because they partly use compression-ignition in their cycle.

There is also a detail difference in the timing of the fuel injection process:

* In the hot-bulb engine, fuel is injected into the vapouriser during the Induction Stroke as air is drawn into the cylinder.

* In the diesel engine, fuel is injected into the cylinder in the final stages of the Compression Stroke.

However, Diesel's original engine design used compressed air to blast the fuel into the cylinder. This complex and heavy system limited the speed the engine could run at and the minimum size a diesel engine could be built to. This was needed to inject fuel under sufficient pressure for it to enter the highly compressed air in the cylinder. In hot-bulb engines fuel is injected before compression takes place, allowing a lighter, more accurate injection system to be used. Only when Akroyd-Stuart's mechanical pump-and-injector system that he developed for his hot-bulb engine was adapted by Robert Bosch for use in diesel engines (by making the system run at a much higher pressure) were high-speed diesel engines practical.

Swashplate engine

The swashplate engine is a type of reciprocating engine that replaces the common crankshaft with a circular plate (the swashplate). Pistons press down on a circular plate in a circular sequence, forcing it to nutate around its center. This motion can be simulated by placing a CD on a ball bearing at its centre and pressing down at progressive places around its circumference. The plate, also known as a wobble plate, is typically geared to produce rotary motion. An alternate design replaces the plate with a sine-shaped cam, and is thus known as a cam engine.

The key advantage of the design is that the cylinders are arranged in parallel around the edge of the plate, and possibly on either side of it as well, and are aligned with the output shaft rather than at 90 degrees as in crankshaft engines. This results in a very compact, cylindrical engine. For this reason the design is also known as a barrel engine.

The arrangement also allows the compression ratio of the engine to be changed whilst running by adjusting the distance of the plate from the cylinders.


Applications

Swashplate engines are particularly interesting in the aircraft engine role, where their compact size is valuable. However, it appears no swashplate engine has ever been widely used in this role, although there have been numerous attempts to introduce one. This may not be any fault of the design, but the designers themselves. It appears that anyone working on these "oddball" engine designs seems to try to include every advanced feature known at the time, instead of using known technology where possible. The result are designs that never seem to mature.

A more successful application is in torpedoes, where the cylindrical shape is desirable. For example, the modern Mark 48 torpedo is powered by a swashplate engine.

Other applications include pneumatic and hydraulic motors and hydrostatic transmissions. Also some Stirling engines use swashplate arrangement.


History

The first known swashplate engine design was introduced by Statax-Motor of Zurich, Switzerland in 1913. Only a single prototype was produced, which is currently held in the Kensington Museum in London. In 1914 the company moved to London to become the Statax Engine Company and planned on introducting a series of rotary engines; a 3 cylinder of 10 hp, a 5 cyl of 40 hp, a 7 cyl of 80 hp, and a 10 cyl of 100 hp. It appears only the 40 hp design was ever produced, and installed in a Caudron G.II for the British 1914 Aerial Derby but was withdrawn before the flight. Hansen introduced an all-aluminum version of this design in 1922, but it is not clear if it was produced in any quantity. Much improved versions were introduced by Statax's German division in 1929, producing 42 hp in a new sleeve valve version known as the 29B. Greenwood and Raymond of San Francisco acquired the patent rights for the US, Canada, and Japan, and planned a 5 cylinder of 100 hp and a 9 cylinder of 350 hp.

Experimental barrel engines for aircraft use were built and tested by Mr J.O. Almen of Seattle, WA in the early 1920s, and by the mid-1920s the water-cooled Almen A-4 (18 cylinders, two groups of nine each horizontally opposed) had passed its United States Air Corps acceptance tests. It however never entered production, reportedly due to limited funds and the Air Corps' growing emphasis on air-cooled radial engines. The A-4 had much smaller frontal area than water-cooled engines of comparable power output, and thereby offered better streamlining possibilities. It was rated at 425 horsepower (317 kW), and weighed only 749 pounds (340 kg), thus giving a power/weight ratio of better than 1:2, a considerable design achievement at the time.

Indian motorcycle also introduced a swashplate engine, the Alfaro, in 1938. The Alfaro is a perfect example of the "put in everything" design, as it included a sleeve valve system based on a rotating cylinder head, a design that never entered production on any engine.

Stephen DuPont in 2006 wrote a small book, A 1911 Spanish Pilot and MIT Aeroengineer and his 1938 Aeroengine Upgraded for Today, ISBN 0-9777134-0-7, which details the development of a barrel engine for aircraft and contains a brief biography of its inventor, Heraclio Alfaro. DuPont was the son of the founder of the Indian motorcycle company; Alfaro was one of his professors at MIT. DuPont later worked further on developing the barrel engine, particlarly for a helicopter, the Doman.

Some small barrel engines were produced by the H.L.F. Trebert Engine Works of Rochester, New York for marine usage.

Perhaps the most refined of the designs was the British Wooler motorcycle engine of 1937. This design used two pistons per cylinder, moving in opposite directions (see the Junkers Jumo 205 for details). The connecting rods attached to a tilting plate through ball joints, and the plate in turn drove a swashplate for power.

More recently, Axial Vector Engine Company has been attempting to re-introduce the concept, although with limited success to date. Their engine, like many of the others on this list, also suffers from the "put in everything" problem, including piezoelectric valves and ignition, ceramic cylinder liners with no piston rings, and a variety of other advanced features.

Axial piston pump

An axial piston pump is a positive displacement pump that has a number of pistons in a circular array within a cylinder block. It can be used as a stand-alone pump or as a hydraulic motor.


Description

An axial piston pump has a number of pistons (usually an odd number) arranged in a circular array within a housing which is commonly referred to as a cylinder block, rotor or barrel. This cylinder block is driven to rotate about its axis of symmetry by an integral shaft that is, more or less, aligned with the pumping pistons (usually parallel but not necessarily).

* Mating surfaces. One end of the cylinder block is flat and wears against a mating surface on a stationary valve plate. The inlet and outlet fluid of the pump pass through different parts of the sliding interface between the cylinder block and valve plate. The valve plate has two semi-circular ports that allow inlet of the operating fluid and exhaust of the outlet fluid respectively.

* Protruding pistons. The pumping pistons protrude from the opposite end of the cylinder block. There are numerous configurations used for the exposed ends of the pistons but in all cases they bear against a cam. In variable displacement units, the cam is movable and commonly referred to as a swash plate, yoke or hanger. For conceptual purposes, the cam can be represented by a plane, the orientation of which, in combination with shaft rotation, provides the cam action that leads to piston reciprocation and thus pumping. The angle between a vector normal to the cam plane and the cylinder block axis of rotation, called the cam angle, is one variable that determines the displacement of the pump or the amount of fluid pumped per shaft revolution. Variable displacement units have the ability to vary the cam angle during operation whereas fixed displacement units do not.

* Reciprocating pistons. As the cylinder block rotates, the exposed ends of the pistons are constrained to follow the surface of the cam plane. Since the cam plane is at an angle to the axis of rotation, the pistons must reciprocate axially as they precess about the cylinder block axis. The axial motion of the pistons is sinusoidal. During the rising portion of the piston's reciprocation cycle, the piston moves toward the valve plate. Also, during this time, the fluid trapped between the buried end of the piston and the valve plate is vented to the pump's discharge port through one of the valve plate's semi-circular ports - the discharge port. As the piston moves toward the valve plate, fluid is pushed or displaced through the discharge port of the valve plate.

* Effect of precession. When the piston is at the top of the reciprocation cycle (commonly referred to as top-dead-center or just TDC), the connection between the trapped fluid chamber and the pump's discharge port is closed. Shortly thereafter, that same chamber becomes open to the pump's inlet port. As the piston continues to precess about the cylinder block axis, it moves away from the valve plate thereby increasing the volume of the trapped chamber. As this occurs, fluid enters the chamber from the pump's inlet to fill the void. This process continues until the piston reaches the bottom of the reciprocation cycle - commonly referred to as bottom-dead-center or BDC. At BDC, the connection between the pumping chamber and inlet port is closed. Shortly thereafter, the chamber becomes open to the discharge port again and the pumping cycle starts over.

* Variable displacement. In a variable displacement unit, if the vector normal to the cam plane (swash plate) is set parallel to the axis of rotation, there is no movement of the pistons in their cylinders. Thus there is no output. Movement of the swash plate controls pump output from zero to maximum.

* Pressure. In a typical pressure-compensated pump, the swash plate angle is adjusted through the action of a valve which uses pressure feedback so that the instantaneous pump output flow is exactly enough to maintain a designated pressure. If the load flow increases, pressure will momentarily decrease but the pressure-compensation valve will sense the decrease and then increase the swash plate angle to increase pump output flow so that the desired pressure is restored. In reality most systems use pressure as a control for this type of pump. The operating pressure reaches, say, 200 bar (2 MPa or 3000 psi) and the swash plate is driven towards zero angle (piston stroke nearly zero) and with the inherent leaks in the system allows the pump to stabilise at the delivery volume that maintains the set pressure. As demand increases the swash plate is moved to a greater angle, piston stroke increases and the volume of fluid increases, if the demand slackens the pressure will rise and the pumped volume diminishes as the pressure rises. At maximum system pressure the output is almost zero again. If the fluid demand increases, beyond the capacity of the pump's delivery, the system pressure will drop near to zero. The swash plate angle will remain at the maximum allowed and the pistons will operate at full stroke. This continues until system flow-demand eases and the pump's capacity is greater than demand. As the pressure rises the swash-plate angle modulates to try to not exceed the maximum pressure while meeting the flow demand.


Design difficulties

Designers have a number of problems to overcome in designing axial piston pumps. One is managing to be able to manufacture a pump with the fine tolerances necessary for efficient operation. The mating faces between the rotary piston-cylinder assembly and the stationary pump body have to be almost a perfect seal while the rotary part turns at, maybe, 3000 rpm. The pistons are usually less than half an inch (13 mm) in diameter with similar stroke lengths. Keeping the wall to piston seal tight means that very small clearances are involved and that materials have to be closely matched for similar coefficient of expansion.

The pistons have to be drawn outwards in their cylinder by some means. On small pumps this can be done by means of a spring inside the cylinder that forces the piston up the cylinder. Inlet fluid pressure can also be arranged so that the fluid pushes the pistons up the cylinder. Often a vane pump is located on the same drive shaft to provide this pressure and it also allows the pump assembly to draw fluid against some suction head from the reservoir, which is not an attribute of the unaided axial piston pump.

Another method of drawing pistons up the cylinder is to attach the cylinder heads to the surface of the swash plate. In that way the piston stroke is totally mechanical. However, the designer's problem of lubricating the swash plate face (a sliding contact) is made even more difficult.

Internal lubrication of the pump is achieved by use of the operating fluid—normally called hydraulic fluid. Most hydraulic systems have a maximum operating temperature, limited by the fluid, of about 120 °C (250 °F) so that using that fluid as a lubricant brings its own problems. In this type of pump the leakage from the face between the cylinder housing and the body block is used to cool and lubricate the exterior of the rotating parts. The leakage is then carried off to the reservoir or to the inlet side of the pump again. Hydraulic fluid that has been used is always cooled and passed through micrometre-sized filters before recirculating through the pump.


Uses

Despite the problems indicated above this type of pump can contain most of the necessary circuit controls integrally (the swash-plate angle control) to regulate flow and pressure, be very reliable and allow the rest of the hydraulic system to be very simple and inexpensive.

Axial reciprocating motors are also used to power many machines. They operate on the same principle as described above, except that the circulating fluid is provided under considerable pressure and the piston housing is made to rotate and provide shaft power to another machine. A common use of an axial reciprocating motor is to power small earthmoving plant such as skid loader machines. Another use is to drive the screws of torpedoes.

Land Rover 2008 LR2

Type:
Five-door,
all-wheel drive luxury small SUV

Retail price:
$34,700 to $40,350

Engine:
3.2-liter inline six-cylinder, 230-hp; 234-pound-feet torque

Transmission:
Six-speed automatic, with clutchless shifting

EPA mileage:
16 mpg city / 23 mpg highway

Notes:
Hits showrooms in April.


Exterior:
Excellent. A distinctive, boxy Land Rover.

Interior:
Good. Luxurious and comfortable, even in the back. Only the cluttered center console kept the rating from being excellent.

Safety:
Excellent. Stability control and roll over control standard. Full set of front, side, and side curtain airbags are standard.

Performance:
Excellent. Performs well on the highway and trails. Engine is powerful and handling is crisp when taking tight mountain turns or making sandy donuts.

Notes:
The LR2 is an excellent vehicle and the price is very competitive when comparing it to other high-end compact SUVs such as the Acura MDX and BMW X3.

2007 Chevrolet Matiz 0.8 SE

Cute, bug-like. Impractical for egoists.

Engine/transmission:
The 2007 Chevrolet Matiz 0.8 SE comes with an 800 cubic centimeter, three-cylinder engine that develops 51 horsepower at 6,000 revolutions per minute and 53 pound-feet of torque at 4,400 rpm. The engine is linked to a four-speed automatic transmission. A five-speed manual gearbox is available.

Body style/layout:
The Matiz, the second generation of a GM Daewoo platform, is a front-engine, front-wheel-drive economy car with four side doors and a rear hatch. It weighs 1,885 pounds.

Ride, acceleration, handling:
City ride, handling and acceleration are good, meaning that the little car holds its own in that driving environment. Lowland highway acceleration is competent, meaning that it can change lanes safely. (The car has a top speed of 83 mph, an illegal speed on most highways worldwide.) Highland driving is both a chore and bore in this one.


Capacities:
There is seating for four. There is enough cargo space for a week's worth of groceries for an American family of four. The fuel tank holds 7.7 gallons of regular unleaded gasoline.

Mileage:
averaged a bit more than 48 miles per gallon in city-highway driving, including a few runs along mountain roads.

Safety:
It has the basics--antilock brakes and dual-front air bags. But no side or head air bags are available at this writing.

Price:
The tested 2007 Chevrolet Matiz 0.8 SE with automatic transmission has a U.S. equivalent price of $13,759. Matiz prices range from $11,861 to $15,925, depending on the model chosen. Chevrolet, at the moment, has no plans to bring this micro car to the United States.

Purse-strings note:
This is a high-value city runner that compares with the Smart Fortwo, sponsored by Mercedes-Benz, which is scheduled to enter the U.S. market in early 2008.

Complaints:
The Matiz is not a mountain car. It crawls about in that milieu. It is competent on lowland highways. But the bottom line is that it is a city automobile that should be kept in the city.

On April 2, 2006 in a 60 Minutes interview with Bob Lutz, part of a prototype Cadillac was revealed to audiences. The car appeared to take design influences both inside and out from the Cadillac Sixteen concept from 2003. Prototype models caught testing at the Nürburgring in Germany also carry many of the design features from the car showcased in April nearly unmasked. Spyshots from the Nürburgring prototypes also show that the car will still have a manual transmission. The CTS will also have an all-wheel drive option.

At the North American International Auto Show in January 2007, GM introduced the all-new CTS that will go on sale as a 2008 model. The base model will feature a 3.6-liter variable valve timing V6 with 258 hp and 252 lb-ft of torque. A second version will be offered, a new 3.6-liter direct-injection V6 VVT engine with an estimated 300 horsepower and 270 pound-feet of torque using regular unleaded gas. A six-speed manual transmission will be standard on all models. The six-speed Hydra-matic 6L50 automatic transmission will be opitional. Also on-demand all-wheel drive will be offered with the 258-hp engine and automatic transmission combo.

The new model is wider and longer with it measuring 191.6 inches (4766 mm) long, 72.5 inches (1841 mm) wide and 58 inches (1472 mm) in height. Wheelbase is 113.4 inches (2880 mm) with a front/rear track of 61.8 / 62.0 inches (1575 / 1585 mm).

Like its predecessor, the 2008 CTS is offered with rear- or, new for 2008, all-wheel-drive. Some suspension, braking, and steering improvements from last year's CTS-V have been added to the standard CTS.

Nine-spoke, 18-inch wheels surround larger high-performance brake calipers and rotors.

Side air extractors are located forward of the front doors.

Optional features include iPod integration, swiveling headlights, Bose premium audio, and remote start.

According to the current issue of Motor Trend, a coupe and station wagon version of the CTS may be produced and sold in the USA, although GM feels that they may be more successful in Europe. Also, an American model of a Cadillac based on the soon to be Saturn Astra may be in the USA as well in Sedan or 4-door hatch form.



2008 Cadillac CTS

TYPE:
Rear-drive or all-wheel-drive, mid-size, five-passenger, luxury sedan.

POWER:
3.6-liter, 300-horsepower, direct-injection VVT V6; six-speed auto transmission.

CHASSIS:
Independent suspension with short/long arm front and multi-link coil springs in rear with load-leveling shocks, stabilizer bar; performance-tuned, speed-sensitive power rack-and-pinion steering; traction control with Stabilitrak; power disc brakes with ABS; dual exhaust.

LENGTH X WIDTH X HEIGHT: 191.6 x 72.5 x 58 inches.

WHEELBASE X TRACK: 113.4 x 61.8/62 inches.

CURB WEIGHT: 3,872 pounds.

STANDARD:
Front/side/head-protection air bags; automatic climate control; power accessories; remote keyless entry; cruise control; AM/FM/CD/MP3 audio system; power-adjustable front seats; leather upholstery; split-folding rear seat; driver info centers, power/heated outside mirrors; fog lamps; twilight sentinel lamps; alarm system.

Porsche Cayenne

The Porsche Cayenne is a mid-size luxury SUV produced by the German automaker Porsche since 2002. It is the first V8 engined vehicle built by Porsche since 1995, when the Porsche 928 was discontinued. Sales of the Cayenne have been strong, with 100,000 sold as of June 2005, becoming Porsche's best-selling vehicle in North America. 40% of Cayenne sales are in North America. Sales slowed by 2006. The Cayenne was skipped for the 2007 model year, but has been redesigned for 2008.



Design

The Cayenne was co-developed with Volkswagen, who were also looking to add a sports utility vehicle to their lineup, as a cost-sharing initiative. Volkswagen share this chassis (the E chassis) to underpin their Touareg sports utility vehicle, and Audi use an extended version for their Q7, although there are numerous styling, equipment and technical differences between the three vehicles. The Cayenne shares only its base engine with the Touareg, and Porsche's version is substantially modified. There are currently 4 engines available in the Cayenne:

* 3.2 L 240 PS (237 hp/177 kW) VR6 from Volkswagen (Based on the unit offered in the VW but with modifications made to the intake, exhaust, timing systems and head)
* 4.5 L 340 PS (335 hp/250 kW) V8 (S)
* 4.5 L 450 hp (340 kW) 460 ft·lbf (624 N·m) twin-turbocharged V8 (Turbo)
* 4.5 L 500 hp (370 kW) 515 ft·lbf (698 N·m) Tequipment twin-turbocharged V8
* 4.5 L 521 hp (389 kW) 531 ft·lbf (720 N·m) twin-turbocharged V8 (Turbo S)


Performance

The turbocharged model has extremely high performance for a sport utility vehicle. It is roughly as quick to 60 miles per hour as the company's Boxster S (about 5.2 seconds), and the new Tequipment special version will be faster still. Reviews indicate that the Cayenne handles remarkably well for a heavy SUV — much better than the BMW X5, which is saying something — whilst having a comfortable ride, and, by some sources, better off-road ability than BMW, Mercedes, and Infiniti. Those cars are, unlike native off-road vehicles, not meant to climb rock mountains and pass deep rivers (due to the price and comfort they offer) but are fully capable to drive "where man need". Many users of SUVs report that car's ability to reach any skiing or recreational center and being comfortable during general winter drive is all they need. Other reasons for buying such cars are increased safety, street overview, and independence on "planned route" - which is why many US-based SUVs and pickups lack even 4-wheel drive or self-locking differentials. The Cayenne does not therefore offer the level of off-road capability of Land Rover products.

The competence, however, comes at a cost, with the "S" V8 model being more expensive than a comparably-specified BMW X5, and the turbocharged model costing nearly US$90,200 before adding options, about as much as a fully equipped, V8 powered Mercedes-Benz S-Class. The Cayenne's rival in terms of cost and prestige is the Land Rover Range Rover, and to a lesser extent the BMW X5. The Mercedes-Benz M-Class and Audi Q7 regrettably fall short of this distinction. The success of the Cayenne has prompted Land Rover to develop the smaller, sportier, and but fully off-road capable Range Rover Sport as well as to offer a supercharged version of their top-range model.

The Cayenne comes standard with alloy rims from 17"-20" sizes and a variety of styles. The least-expensive Cayenne model comes standard with the 17" rims, but has the cability to upgrade to any of the four 18"-20" rims. An all-season tire is standard on the 17" rim, and available as a no-cost option for 18" rims. These are the wheels that are most suitable for off-road/snow use. Lower-profile, high performance tires are standard for wheels above 19". These tires would not be suitable for off-road/snow use. Porsche/Volkswagen jointly did extensive off-road testing with the Cayenne and Touareg and actually both are not so capable off-road even though. Both vehicles come standard with 4-wheel drive, a manually lockable center differential and a "low range" setting. Options to make the vehicles more capable off-road include an available air suspension system which can raise the car's ride height on command and an interior switch allowing the rear differential to be manually locked along with the center unit. At maximum ride height, the air suspension system gives the Cayenne 10.7 inches (272 mm) of ground clearance.


Cayenne Turbo S

Porsche introduced a higher-output Turbo S version at the 2006 Los Angeles Auto Show to compete with the Mercedes-Benz ML63 AMG, which produces 510 hp (375 kW) and accelerates from 0-100 km/h (62 mph) in 4.8 seconds. The Turbo S produces 520 hp (389 kW) and 531 ft·lbf (720 N·m), making it the second most powerful vehicle Porsche has ever built for the road, after the Carrera GT. It is able to accelerate to 60 mph quicker than the Cayman S at 5.1 seconds (mfg. claim). It releases 378 gCO2/km.

The Turbo S also has a recalibrated suspension, 20 inch wheels, and larger brake discs. It lowers 27 mm above 125 km/h and 11 mm more above 210 km/h.


Hybrid

At the IAA 2005, Porsche announced it will produce a hybrid version of the Cayenne before 2010.

Recently, Michael Winkler, managing director of Porsche Australia, revealed that a hybrid Cayenne would be available in Australia in 2009.[1]. Winkler also said that the system is designed to work with all of the engines in the Cayenne lineup. This means a hybrid Cayenne Turbo could be possible. The hybrid will only be mated to the all wheel drive system and won't be offered in any other models.


Controversy

Many Porsche enthusiasts are unhappy with the company for producing an SUV, seeing it as diluting the meaning of the brand. According to Wheels, a well-regarded Australian car magazine, the decision to develop the Cayenne was a contentious one for the company for this reason. Management reportedly felt, however, that the company needed a more dependable source of revenue than the fickle sports car market. Much of the disapproval from Porsche owners come from the joint development of the car with Volkswagen. Although both the Cayenne and Touareg are solid SUVs in the market today, many believe the Cayenne would be superior in many departments if developed solely by Porsche. Some believe the Touareg is a better executed car available for significantly less money. British motoring journalist Jeremy Clarkson put it: "It's not a bad car and in many respects it's a very good one, but just as no-alcohol lager defeats the objective, so does a Porsche off-roader. Can you imagine Land Rover producing a rear engined sports car? Exactly".

In May 2004, Porsche issued a recall on the Cayennes for seatbelts that do not function properly during a collision.

It is also rumored that Porsche could produce a second SUV, smaller, shorter, less powerful and based on the Audi Q5.


Engines:
3.6-liter V-6, 290-hp, 273-lb-ft
4.8-liter V-8, 385-hp, 369-lb-ft
4.8-liter turbo V-8, 500-hp, 516-lb-ft
All engines require premium fuel

Transmission:
Six-speed manual, six-speed automatic with clutch less shifting available.

EPA mileage:
3.6-liter: 14 mph city / 20 mpg highway
4.8-liter : 13mpg / 19 mpg
4.8-liter turbo: 12 mpg / 19 mpg

Notes:
An exceptional SUV with excellent performance but price rises sharply for fully loaded models.

Integrated Motor Assist

Integrated Motor Assist (commonly abbreviated as IMA) is Honda's hybrid car technology, introduced in 1999 on the Insight. It uses an electric motor mounted between the engine and transmission to act as a starter motor, engine balancer, and assist traction motor. In its first generation, IMA could not power the car on electricity alone, and could only use the motor to assist or start the engine. The 2006 Civic Hybrid, however, can activate the electric motor while the vehicle is coasting without turning the ICE on, though in contrast to Toyota's Hybrid Synergy Drive (HSD) or General Motors and DaimlerChrysler's Global Hybrid Cooperation, the IMA has a less powerful motor/generator which allows the car to slow or stop its rate of deceleration to a lesser extent; it cannot operate without turning over the ICE which is directly coupled to its electric motor.

The theory behind IMA is to use regenerative braking to recapture some of the energy lost through deceleration, and reuse that energy later on to help accelerate the vehicle. This has two effects: it increases the rate of acceleration, and it reduces the work required of the gasoline engine. The acceleration boost is important as it allows the engine to be scaled down to a smaller but more fuel-efficient variant without rendering the vehicle overly slow or weak. This smaller engine is the primary reason cars equipped with IMA get better highway mileage than their more conventional counterparts.

Additionally, vehicles equipped with IMA can shut off their engine when the vehicle stops and use the electric motor to rapidly spin it back up when the driver releases the brake pedal. They also have a conventional starter as a backup, making it the only production hybrid system which can operate with its high voltage electric system disabled, using only its ICE like a traditional vehicle. However, since the IMA also acts as the vehicle's alternator, eventually the 12 V accessory battery would require an external charge.

Honda produced a high-performance IMA motor for the Dualnote concept car. The engine was a 3.5 liter DOHC i-VTEC V6 motor featuring "new-generation" IMA. It was estimated to produce 400 horsepower while still being capable of fuel efficiency of approximately 18 km/liter (42 mpg).

DaimlerChrysler BlueTec

BlueTec is DaimlerChrysler's name for its two nitrogen oxide (NOx) reducing systems, for use in their Diesel automobile engines. One is a urea based reductant called AdBlue, the other is called DeNOx and uses an oxidising catalytic converter and particulate filter combined with other NOx reducing systems. Both systems are designed to reduce pollutant emissions.

The BlueTec was on the Ward's 10 Best Engines list for 2007.



Uses

Mercedes-Benz introduced the systems in the E-Class (using the 'DeNOx' system) and GL-Class (using 'AdBlue') at the 2006 North American International Auto Show as the E320 and GL320 Bluetec vehicles. This system makes these vehicles 45-state and 50-state legal, respectively in the United States, and is expected to meet all emissions regulations through 2009.

A Jeep Grand Cherokee with the same Bluetec engine is also expected, and Mercedes announced tentative plans for a BLUETEC/electric hybrid S-Class.

Volkswagen has introduced the Jetta Clean TDI, the Tiguan concept and the VW Touareg BlueTDI as part of the BlueTec program. All are expected to be introduced in the American market in 2008. The Jetta and the Tiguan use NOx Adsorbers, while the Toureg uses a Selective Catalytic Reduction catalystic converter.

DaimlerChrysler has entered an into agreement with Volkswagen and Audi to share BlueTec technology with them in order to increase the Diesel passenger-vehicle market in the US.


Rationale

The BlueTec system was created because the processes that give diesel engines efficient fuel economy also creates extra emissions of certain pollutants. High compression ratios and lean air-fuel mixtures make high combustion temperatures, which results in more nitrogen oxides and Diesel Particulate Matter (also known as smoke) being released into the atmosphere. While the particulate matter can be controlled with higher injection pressures and particulate filters, the big challenge is limiting NOx (Tier 2 regulations in the US are 0.05 gram per mile of NOx, which is ⅛ of the 0.40 limit in the European Union).


Process

The Bluetec system will use two catalytic converters specifically targeting NOx. The first converter traps the NOx, and later releases it to the second converter which then converts it to nitrogen (N2) and water (H2O). This will make a diesel car legal in 45 states. But to make it pass the more stringent regulations of California, Maine, Massachusetts, New York and Vermont, AdBlue (NH4) will have to be introduced into the system, making the conversion more complete.



The whole exhaust system would work like so:

1. A Diesel oxidation catalyst reduces carbon monoxide (CO) and hydrocarbons (HC) released from the exhaust.

2. A DeNOx catalytic converter begins a preliminary removal of oxides of nitrogen.

3. A particulate filter will trap and store smoke particles, burning them off when the filter gets full.

4. If the above are not sufficient to meet the exhaust specifications, a Selective Catalytic Reduction (SCR) catalytic converter will take the remaining nitrogen oxides and covert them to nitrogen and water. AdBlue will be injected into it to help the conversion.

Antiknock agent

An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating.

The mixture known as gasoline, when used in high compression internal combustion engines, has a tendency to ignite early (pre-ignition or detonation) causing a damaging "engine knocking" (also called "pinging" or "pinking") noise. Early research into this effect was led by A.H. Gibson and Harry Ricardo in England and Thomas Midgley and Thomas Boyd in the United States. The discovery that lead additives modified this behavior led to the widespread adoption of the practice in the 1920s and therefore more powerful higher compression engines. The most popular additive was tetra-ethyl lead. However, with the discovery of the environmental and health damage caused by the lead, and the incompatibility of lead with catalytic converters found on virtually all US automobiles since 1975, this practice began to wane in the 1980s. Most countries are phasing out leaded fuel; different additives have replaced the lead compounds. The most popular additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol).

The typical antiknock agents in use are:

* Tetra-ethyl lead (phased out)
* Methylcyclopentadienyl manganese tricarbonyl (MMT)
* Ferrocene
* Iron pentacarbonyl
* Toluene
* Isooctane


Tetra-ethyl lead

In the U.S., where lead was blended with gasoline (primarily to boost octane levels) since the early 1920s, standards to phase out leaded gasoline were first implemented in 1973. In 1995, leaded fuel accounted for only 0.6 % of total gasoline sales and less than 2,000 tons of lead per year. From January 1, 1996, the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum $10,000 fine in the United States. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines until 2008. The ban on leaded gasoline led to thousands of tons of lead not being released in the air by automobiles. Similar bans in other countries have resulted in lowering levels of lead in people's bloodstreams.

A side effect of the lead additives was protection of the valve seats from erosion. Many classic cars' engines have needed modification to use lead-free fuels since leaded fuels became unavailable. However, "Lead substitute" products are also produced and can sometimes be found at auto parts stores.

Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates.

In some parts of South America, Asia and the Middle East, leaded gasoline is still in use. Leaded gasoline was phased out in sub-Saharan Africa with effect from 1 January, 2006. A growing number of countries have drawn up plans to ban leaded gasoline in the near future.

To avoid deposits of lead inside the engine, lead scavengers are added to the gasoline together with tetra-ethyl lead. The most common ones are:

* Tricresylphosphate
* 1,2-Dibromoethane
* 1,2-Dichloroethane


MMT

Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used for many years in Canada and recently in Australia to boost octane. It also helps old cars designed for leaded fuel run on unleaded fuel without need for additives to prevent valve problems.

US Federal sources state that MMT is suspected to be a powerful neurotoxin and respiratory toxin, and a large Canadian study concluded that MMT impairs the effectiveness of automobile emission controls and increases pollution from motor vehicles.

Uniflow steam engine

The uniflow type of steam engine uses steam that flows in one direction only in each half of the cylinder. Thermal efficiency is increased in the compound and multiple expansion types of steam engine by separating expansion into steps in separate cylinders; in the uniflow design, thermal efficiency is achieved by having a temperature gradient along the cylinder. Steam always enters at the hot ends of the cylinder and exhausts through ports at the cooler centre. By this means the relative heating and cooling of the cylinder walls is reduced.


Design details

Steam entry is usually controlled by poppet valves (which act similarly to those used in internal combustion engines) that are operated by a camshaft. The inlet valves open to admit steam when minimum expansion volume has been reached at the start of the stroke. For a period of the crank cycle steam is admitted and the poppet inlet is then closed, allowing continued expansion of the steam during the stroke, driving the piston. Near the end of the stroke the piston will expose a ring of exhaust ports mounted radially around the centre of the cylinder. These ports are connected by a manifold and piping to the condenser, lowering the pressure in the chamber to below that of the atmosphere causing rapid exhausting. Continued rotation of the crank moves the piston. From the animation the features of a uniflow engine can be seen, with a large piston almost half the length of the cylinder, poppet inlet valves at either end, a camshaft (whose motion is derived from that of the driveshaft) and a central ring of exhaust ports.


Advantages

Uniflow engines potentially allow greater expansion in a single cylinder without the relatively cool exhaust steam flowing across the hot end of the working cylinder and steam ports of a conventional "counterflow" steam engine during the exhaust stroke. This condition allows high thermal efficiency. The exhaust ports are only open for a small fraction of the piston stroke, therefore not all of the expanded steam is able to exhaust. This remaining steam is compressed by the returning piston and is thermodynamically desirable as it preheated the hot end of the cylinder before the admission of steam. However, the risk of excessive compression often resulted in small auxiliary exhaust ports being included at the cylinder heads. Such a design is called a semi-uniflow engine.

Engines of this type usually have multiple cylinders in an inline arrangement and may be single or double acting. A particular advantage of this type is that the valves may be operated by the effect of multiple camshafts, and by changing the relative phase of these camshafts, the amount of steam admitted may be increased for high torque at low speed and may be decreased at cruising speed for economy of operation, and by changing the absolute phase the engine's direction of rotation may be changed. The uniflow design also maintains a constant temperature gradient through the cylinder, avoiding passing hot and cold steam through the same end of the cylinder.



Disadvantages

In practice the uniflow engine has a number of operational shortcomings. The large expansion ratio requires a large cylinder volume. To gain the maximum potential work from this a high reciprocation rate was required, typically 80% faster than a double-acting engine. This caused the opening times of the inlet valves to be very short, putting great strain on a delicate mechanical part. In order to withstand the huge mechanical forces encountered, engines had to be heavily built and a large flywheel was required to smooth out the variations in torque as the steam pressure rapidly rose and fell in the cylinder. Additionally, as there was a thermal gradient across the cylinder, the metal of the wall expanded to different extents. This required precise boring of the cylinder barrel to be wider in the cool centre than at the hot ends. If the cylinder was not heated correctly, or if water entered, the delicate balance could be upset causing seizure mid-stroke or, potentially, destruction.



History

The uniflow engine was first used in Britain in 1827 by Jacob Perkins and was patented in 1885 by Leaonard Jennett Todd. It was popularised by German engineer Johann Stumpf in 1909, with the first commercial stationary engine produced a year previously in 1908.

The uniflow principle was mainly used for in industrial power generation, but was also tried in a few railway locomotives in England, such as The NER Uniflow Locomotive No 825 of 1913, The NER Uniflow Locomotive No 2212 of 1919, and The Midland Railway Paget locomotive. Experiments were also made in the USA and Russia. In no case were the results encouraging enough for further development to be undertaken.

The final commercial evolution of the Uniflow engine occurred in the USA during the late 1930s and 1940s by the Skinner Engine Company with the development of the Compound Unaflow Marine Steam Engine. This engine operated in a steeple compound configuration and provided efficiencies approaching contemporary diesels. Many bulk carriers and ferries on the Great Lakes were so equipped, several of which are still operating.

In small sizes (less than about 1000 horsepower ), reciprocating steam engines are much more efficient than steam turbines. The Whitecliffs solar steam power plant uses a three cylinder uniflow engine to generate about 25 kW electric output.

What is a Timing Curve?

The timing curve is the mechanical timing values plotted over an RPM curve. What this means is that at a given RPM based upon the weights and springs used in the distributor you will have a specified amount of timing advance. Remember, as your engine RPM increases, so does the inertia against the distributor weights within the distributor. The springs holding the weights is the opposite resistance force that controls the speed, or rate, that the weights move "out" causing the distributor advance plate to move which advances the timing. So, what happens is that at each RPM change there is a variance in the amount of timing advance up to a point in which the weights usually hit a "stop" that does not allow them to move out (advance the distributor) beyond that point.

Changing the springs to a lighter one (or both) will make the advance occur faster, and of course running a heavier (stronger) spring will slow the advance rate. You can also in most cases modify the weights (or stops) as to what the advance limit will be. Mixing springs to control the desired advance rate is how you modify your timing curve.

What is Initial Timing and Total Timing?

Initial timing is that setting you make while your engine is idling with a timing light. This is typically between 4° ATDC (After Top Dead Center) to 16° BTDC (Before Top Dead Center). For performance applications "in most cases" you want as much initial timing as the starter can handle (the more timing the more cylinder pressure that the starter must overcome to crank the engine). Too much initial timing, besides the starter load, can also run the HC (Hydrocarbon) emission levels beyond legal or breathable levels .

Total timing is the calculation of the combined initial and mechanical advance timing settings (max). This "can" also include your vacuum advance though, I like to describe it as "total timing plus vacuum advance". Since vacuum advance is a nearly inconsistent value I like to use it after I have set up the correct mechanical values in the distributor. At times I must use the vacuum advance to generate the timing values I require, but I try to only use it as an "economy" tool to give a street driven vehicle more efficiency and throttle response by this addition.

Ignition timing

Ignition timing in an internal combustion engine is the process of setting the time that a spark will occur in the combustion chamber (during the power stroke) relative to piston position and crankshaft angular velocity. Setting the correct ignition timing is crucial in the performance of an engine. The ignition timing affects many variables including engine longevity, fuel economy, and engine power. Modern engines that are controlled by an engine control unit use a computer to control the timing throughout the engine's RPM range. Older engines that use mechanical spark distributors rely on inertia (by using rotating weights and springs) and manifold vacuum in order to set the ignition timing throughout the engine's RPM range. There are many factors that influence ignition timing. These include which type of ignition system is used, engine speed and load, which components are used in the ignition system, and the settings of the ignition system components. Usually, any major engine changes or upgrades will require a change to the ignition timing settings of the engine.



History

The ignition systems of older, non-computer controlled engines consists of a mechanical spark distributor which distributes spark to cylinders based on an initial timing advance, mechanical timing advance, and vacuum timing advance. In 1972, Chrysler introduced the electronic ignition system that controlled ignition timing and fuel delivery, replacing the mechanical spark distributor and therefore mechanical and vacuum timing advance. This system led to the advanced automobile electronic systems of today’s automobiles. Ignition systems will continue to improve as ignition components become more technologically advanced.


Setting the Ignition Timing

“Timing advance” refers to the number of degrees before top dead center (BTDC) that the spark will ignite the air-fuel mixture in the combustion chamber during the power stroke. “Timing retard” refers to the number of degrees after top dead center (ATDC) that the spark will ignite the air-fuel mixture during the power stroke.

Timing advance is required because it takes time to burn the air-fuel mixture. Igniting the mixture before the piston reaches top dead center (TDC) will allow the mixture to become fully burnt soon after the piston reaches TDC. If the air-fuel mixture is ignited at the correct time, maximum pressure in the cylinder will occur sometime after the piston reaches TDC allowing the ignited mixture to push the piston down the cylinder. Ideally, the time at which the mixture should be fully burnt is about 20 degrees ATDC. This will utilize the engines power producing potential. If the ignition spark occurs at a position that is too advanced relative to piston position, the rapidly expanding air-fuel mixture can actually push against the piston causing detonation and lost power. If the spark occurs too retarded relative to the piston position, maximum cylinder pressure will occur after the piston is already traveling too far down the cylinder. This results in lost power, high emissions, and unburned fuel.

The ignition timing will need to become increasingly advanced (relative to TDC) as the engine speed increases so that the air-fuel mixture has the correct amount of time to fully burn. Another reason for advancing the timing is because as the engine speed increases, fuel consumption increases. Since more fuel is present in the cylinder, the time required to fully burn the air-fuel mixture will be longer. Poor volumetric efficiency at lower engine speeds also requires increased advancement of ignition timing. The correct timing advance for a given engine speed will allow for maximum cylinder pressure to be achieved at the correct crankshaft angular position. When setting the timing for an automobile engine, the factory timing setting can usually be found on a sticker in the engine bay.


Dyno Tuning

Setting the ignition timing while monitoring engine power output with a dynamometer is an excellent way to correctly set the ignition timing. After advancing or retarding the timing, a corresponding change in power output will usually occur. Using a knock sensor to find the correct timing is one method used to tune an engine. In this method, the timing is advanced until knock occurs. The timing is then retarded one or two degrees and set there. After achieving the desired power characteristics for a given engine load/rpm, the spark plugs should be inspected for signs of engine detonation. If there are signs of detonation, the ignition timing should be retarded until there are no signs of detonation.


Mechanical Ignition Systems

Mechanical ignition systems use a mechanical spark distributor to distribute a high voltage current to the correct spark plug at the correct time. In order to set an initial timing advance or timing retard for an engine, the engine is allowed to idle and the distributor is adjusted to achieve the best ignition timing for the engine at idle speed. This process is called 'setting the base advance'. There are two methods of increasing timing advance past the base advance. The advances achieved by these methods are added to the base advance number in order to achieve a total timing advance number.


Mechanical Timing Advance

An increasing mechanical advancement of the timing takes place with increasing engine speed. This is possible by using the law of inertia. Weights and springs inside the distributor rotate and affect the timing advance according to engine speed. This type of timing advance is also referred to as centrifugal timing advance. The amount of mechanical advance is dependant solely on the speed at which the distributor is rotating. In a 2-stroke engine, this is the same as engine RPM. In a 4-stroke engine, this is half the engine RPM. The relationship between advance in degrees and distributor RPM can be drawn as a simple 2-dimensional graph.

Lighter weights or heavier springs can be used to reduce the timing advance at lower engine rpm's. Heavier weights or lighter springs can be used to advance the timing at lower engine rpm's.

Most vehicle manufacturers specify that the vacuum line for the vacuum advance (if equipped) should be disconnected and plugged when setting the initial advance. Be careful when turning the distributor while the engine is running because deteriorated spark plug wires can deliver a dangerous shock.


Vacuum Timing Advance

The second method used to advance the ignition timing is called vacuum timing advance. This method is sometimes (depending on the engine manufacturer) used in addition to mechanical timing advance. Usually, this method is used to increase fuel economy. Vacuum advance works by using a vacuum source to advance the timing at mid engine load conditions. Vacuum advance is diminished at wide open throttle (WOT), causing the timing advance to return to the base advance in addition to the mechanical advance.

The most common vacuum source for vacuum advance is a small port located in the wall of the throttle body or carburetor adjacent to but slightly upstream of the edge of the throttle plate. In carburetors having primary and secondary throttle plates, the port is located in the primary. The effect of having a hole here is that there is little or no vacuum at idle or at wide open throttle, with the vacuum signal peaking at part throttle opening.

On some vehicles, a temperature sensing switch will apply manifold vacuum to the vacuum advance system when the engine is overheating. The purpose of this is to increase engine speed to turn the engine fan faster to try to overcome the overheating.

On some vehicles, some form of switches may be used to prevent vacuum advance under certain conditions such as when the engine is cold or depending on what gear the vehicle is in. This is usually because these are necessary to comply with emission standards.


Electronic Ignition Systems

Newer engines typically use electronic ignition systems (ignition controlled by a computer). The computer has a timing map which is a chart with engine speed on one axis and engine load on another axis. Timing advance numbers are inserted in this chart. The computer will send a signal to the ignition coil at the indicated time in the timing map in order to spark the spark plug. Most computers from original equipment manufacturers (OEM) are not able to be modified so changing the timing advance is not possible. Aftermarket engine control units allow the user to make changes to the timing map. This allows the timing to be advanced or retarded based on various engine applications.

Lean burn

Lean burn is an internal combustion of lean air-fuel mixtures. It happens at very high air-fuel ratios (up to 65:1), so the mixture has considerably less amount of fuel in comparison to stoichiometric combustion ratio (14.6:1 for petrol).

The engines designed for lean burning can employ higher compression ratios and thus provide better performance, efficient fuel use and low exhaust emissions than those found in conventional petrol engines. Ultra lean mixtures with very high air-fuel ratios can only be achieved by Direct Injection engines.

The main drawback of lean burning is the large amount of NOx being generated, so a complex catalytic converter system is required. Lean burn engines do not work well with modern 3-way catalytic converters, which require a balance of pollutants at the exhaust port in order to carry out both oxidation and reduction reactions, so most modern engines run at or near the stoichiometric point.


Chrysler Lean Burn computer

From the late 1970s to mid 1980s, Chrysler equipped many of its North American production cars with a spark control computer which it called the Lean Burn Computer on the large sticker on the unit.

Mounted on the air filter housing of most rear-wheel drive cars Chrysler produced during this time, it was responsible for adjusting spark timing based on manifold vacuum, engine speed, engine temperature and incoming air temperature; by doing this, Chrysler eliminated the traditional vacuum and centrifugal timing advance mechanisms used on distributors in order to provide more accurate spark timing. It also provided drive for the ignition coil directly, eliminating the separate ignition module.

Based on an early computer system, most Lean Burn computers were an open-loop emissions control system with no provided diagnostic port or "Check Engine" warning light, were difficult to troubleshoot, and were greatly responsible for the poor reliability reputation which dogged Chrysler at the time.

Many Lean Burn computers were replaced with the more reliable electronic ignition module and centrifugal/vacuum advance distributors used on earlier Chrysler vehicles, almost universally to improvements in fuel economy and driveability.


Heavy-duty gas engines

Lean burn concepts are often used for the design of heavy-duty natural gas, biogas, and liquefied petroleum gas (LPG) fuelled engines. These engines can either be full-time lean burn, where the engine runs with a weak air-fuel mixture regardless of load and engine speed, or part-time lean burn (also known as "lean mix" or "mixed lean"), where the engine runs lean only during low load and at high engine speeds, reverting to a stoichiometric air-fuel mixture in other cases.

Heavy-duty lean burn gas engines admit as much as 75% more air than theoretically needed for complete combustion into the combustion chambers. The extremely weak air-fuel mixtures lead to lower combustion temperatures and increased forced induction possibilities (that would otherwise be limited by high exhaust gas temperatures), leading to higher theoretical efficiencies when compared to engines running on a stoichiometric air-fuel mixture.


Honda lean burn systems

One of the newest lean-burn technologies available in automobiles currently in production uses very precise control of fuel injection, a strong air-fuel swirl created in the combustion chamber, a new linear air-fuel sensor (LAF type O2 sensor) and a lean-burn NOx catalyst to further reduce the resulting NOx emissions that increase under "lean-burn" conditions and meet NOx emissions requirements.

This stratified-charge approach to lean-burn combustion means that the air-fuel ratio isn't equal throughout the cylinder. Instead, precise control over fuel injection and intake flow dynamics allows a greater concentration of fuel closer to the spark plug tip (richer), which is required for successful ignition and flame spread for complete combustion. The remainder of the cylinders' intake charge is progressively leaner with an overall average air:fuel ratio falling into the lean-burn category of up to 22:1.

The older Honda engines that used lean burn (not all did) accomplished this by having a parallel fuel and intake system that fed a pre-chamber the "ideal" ratio for initial combustion. This burning mixture was then opened to the main chamber where a much larger and leaner mix then ignited to provide sufficient power. During the time this design was in production this system (CVCC, Compound Vortex Controlled Combustion) primarily allowed lower emissions without the need for a catalytic converter. These were carburated engines and the relative "imprecise" nature of such limited the MPG abilities of the concept that now under MPI (Multi-Port fuel Injection) allows for higher MPG too.

The newer Honda stratified charge (lean burn engines) will operate on air-fuel ratios as high as 22:1. The amount of fuel drawn into the engine is much lower than a typical gasoline engine which operates at 14.7:1. That being the chemical stoichiometric ideal for complete combustion when averaging gasoline to be the petrochemical industries' accepted standard of C6H8.

This lean-burn ability by the necessity of the limits of physics, and the chemistry of combustion as it applies to a current gasoline engine must be limited to light load and lower RPM conditions. A "top" speed cut-off point is required since leaner gasoline fuel mixtures burn slower and for power to be produced combustion must be "complete" by the time the exhaust valve opens.


Applications

* 1993–95 Civic VX
* 1998–2000 Civic Hx
* 2001 Civic Hx
* 2002–06 Civic Hybrid
* 2000–06 Insight


Diesel engines

All diesel engines are lean burning. This is essential to the way they ignite the fuel.

Hit and miss engine

A type of four-stroke internal combustion engine that was commonly used in the early part of the 1900s. They serve no commercially significant function today and are mainly owned by hobbyists.

A typical hit and miss engine had a power of 2 to 10 HP and ran under full load at speeds of 400 to 1,000 RPM. They were used to power pumps for cultivation, saws, generators and other small stationary applications. They were used in applications where cost was a consideration and their simplicity of design reflected that requirement.

The term "hit and miss" comes from the sound that the engine makes when running at idle. The sound is most like an engine that is barely running: missing on several strokes and then hitting on one. Just hitting enough to keep the engine turning.

These were simple engines but they incorporated some very clever governor designs. It may be the originality in the design of the governor that is so fascinating for the hobbyist/collector. There is great variation in governor design from one manufacturer to another so there is no general design that will describe all engines.

Things that are common to most engines: there is no intake cam, the exhaust valve is held open to prevent the engine from building up compression or firing until the speed decreases, when the speed does decrease, the exhaust valve closes. A governor controls the exhaust valve and the magneto spark.

In operation: the engine fires and this increases its speed. The increased speed causes the governor to open the exhaust valve and to cut off the magneto spark. The engine then turns freely for several revolutions but slows to a point where the governor closes the exhaust valve. On the next downstroke of the piston, the closed combustion chamber draws a vacuum, the vacuum pulls the intake valve open and draws fuel and air into the combustion chamber. The piston then compresses the mixture, the spark ignites it and the engine is given one power stroke which increases its speed.

The number of power strokes to non-power strokes is a function of the load on the engine. When the engine is unloaded the ratio is several non-power strokes for each power stroke and the engine has its characteristic sound.

4-stroke power valve system

A 4-stroke powervalve is a device fitted to 4 stroke engines that constantly adjusts the internal diameter of the exhaust system to perfectly suit engine revolutions.

This ensures superior low to mid-range performance (ca. 12-20% improvement), linear power output and reduced exhaust noise levels while the valve is in its reduced opening position.

* Yamaha EXUP (Exhaust Ultimate Power valve)
* Honda HTEV (Honda Titanium Exhaust Valve)
* Suzuki SET (Suzuki Exhaust Tuning)

Ferox (fuel additive)

Ferox is a fuel additive. It was developed by Wesley Parish in 1985 from work done on experimental burn rate modifiers for solid rocket propellant systems used in the aerospace industry. Ferox was originally designed to lengthen the life engines. Until recently, it has been used predominantly in the marine, mining, and trucking industries. It is now used as a fuel additive in common automobile engines using gasoline, diesel, and others. The newest form is in a small tablet that is added with fuel into the tank to be dissolved.

There is evidence that ferox can lower polluting emissions, improve gas mileage, and reduce deposit build-up. There are also claims of prolonging engine life. However, the extent of these benefits for average fuel consumers is still not clear.

The product has been registered with the Environmental Protection Agency.

Ferox works as a catalyst, which lowers the activation energy of the rate determining step to break down build-up within the engine. This allows the carbon deposits to burn off at much lower temperatures.

V-Mounted Intercoolers

The V-Mounted Intercooler is a hybrid system, developed to provide superior air cooling to a front mounted intercooler, yet still retain the short intake piping and radiator airflow of the TMIC. In this case, the intercooler is mounted horizontally, directly in front of the engine (although it can be at an angle). Most VMIC setups place the radiator below the intercooler, at a great angle, tilted back until it is almost touching the motor. Ducts are used in the front of the car to duct air through the intercooler, creating a ram-air effect, while the remainder of the air flows over the radiator, normally. The air is usually removed via a hood vent (a vent recessed into the car's hood near the front of the car; if it is mounted too far back, it will actually suck air into the engine bay), although in the case of a bottom-mounted intercooler, the air is allowed the exit underneath the car (although this is dangerous because is places the intercooler at extreme risk to damage from bumps and rocks). VMIC setups are typically utilized on Front Midship cars, as the location of the engine, far back in the engine bay, allows room for the system.

VMICs were pioneered on the Mazda RX-7, because rotary engines have a tendency to run hot. It was intended to be a compromise between a TMIC or a side-mounted intercooler (2nd Generation and 3rd Generation RX-7, respectively) and a FMIC. An intercooler in the stock position would not support high airflow (and thus limit top power, or create severe detonation in the engine, which damages rotary engines more easily than piston engines), while FMICs would block airflow to the radiator, leading to overheating. The RX-7 is the only car that currently has a VMIC kit available for it. VMICs on other cars are custom made, usually used on track cars and require significant investment and fabricating skills to properly set up and tune.

Front Mount InterCooler

FMICs generally require open bumpers, and front spoilers, which will force air into the bumper and provide down force as well, are also beneficial. In general, because of the location, a front mount intercooler tends to cool air more efficiently than a similarly sized TMIC (top mount intercooler) or a SMIC (side mount intercooler). FMICs have some disadvantages, however. One obvious drawback is the vulnerable position of the intercooler in front of the car - any moderately serious frontal impact will significantly damage the FMIC. FMICs, by virtue of their sitting in front of the radiator, block airflow to the radiator, as the air that passes through the intercooler is several degrees hotter than the air on the other side. While on most piston engines, this is not too major a concern, on hot-running engines, and rotary engines in particular, this can lead to problems. FMICs also require the most plumbing of any intercooler setup, which means that there is much more volume that the turbocharger or supercharger must pressurise before it can deliver positive boost. Because of this, many manufacturers opt to use SMICs or TMICs to avoid excessive turbo lag. Several manufacturers including Ford (with the 2003/04 Mustang Cobra and 2007 GT 500), Mitsubishi (Lancer Evolution) and Dodge (2003-05 SRT-4) are shipped from the factory with FMIC's.

The Gerotor

A Gerotor is a positive displacement pumping unit. The name gerotor is derived from "Generated Rotor". A Gerotor unit consists of an inner and outer rotor. The inner rotor has N teeth, and the outer rotor has N+1 teeth. One rotor is located off-center and both rotors rotate. During part of the assembly's rotation cycle, the area between the inner and outer rotor increases, creating a vacuum. This vacuum creates suction, and hence, this part of the cycle is where the intake is located. Then, the area between the rotors decreases, causing compression. During this compression period, fluids can be pumped, or compressed (if they are gasseous fluids).

A gerotor can also function as a motor. High pressure gas enters the intake area and pushes against the inner and outer rotors, causing both to rotate as the area between the inner and outer rotor increases. During the compression period, the exhaust is pumped out. This is an Otto cycle engine.

An engine created by the Starrotor Corporation combines both uses of a gerotor. It uses the Brayton cycle, the same thermodynamic cycle employed by jet engines. A first gerotor compresses gas, this gas is then ignited in a combustor. The gaseous products of this combustion have a much higher pressure, which drives a second gerotor. Then, some of the output of the second gerotor is used to drive the 1st.

Longitudinal engine

In automotive engineering, a longitudinal engine, also sometimes known as a north-south engine, is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back. Most rear wheel drive vehicles use this engine orientation, while most front wheel drive vehicles use a side-to-side transverse arrangement. An exception is most Audi vehicles (those not using Volkswagen-based platforms) which continue to use the longitudinal layout even with larger displacement engines.

A common example of a longitudinal engine is the Boxer engine. This is a design where the cylinders are horizontally opposed, or facing each other. Common cars that share this design are: Alfa Romeo Alfasud (Flat-4), Alfa Romeo 145/146 (Flat-4), the Subaru Impreza (Flat-4) and the Porsche Boxster (Flat-6).

Cylinder head porting

Cylinder head porting is the technology of modifying the intake and exhaust ports of an internal combustion engine to improve the quality and quantity of the gas flow. Cylinder heads as manufactured cannot be optimal due to design and manufacturing constraints. Porting the heads provides the finely detailed attention required to bring the engine to the highest level of efficiency. More than any other single factor porting technology is responsible for the high power output of modern engines.

This process can be applied to a standard racing engine to optimize its power output as well as to a production engine to turn it into a racing engine, to enhance its power output for daily use or to alter its power output characteristics to suit a particular application.

Daily human experience with air gives the impression that air is light and nearly non-existent as we move slowly through it. An engine running at high speed experiences a totally different substance. In that context, air can be thought of as thick, sticky, elastic, gooey and heavy (see viscosity). Pumping it is a major problem for engines running at speed. Porting helps engines deal with this problem.

Valve timing

In a piston engine, the valve timing is the precise timing of the opening and closing of the valves.

In four-stroke cycle engines and some two-stroke cycle engines, the valve timing is controlled by the camshaft. It can be varied by modifying the camshaft, or it can be varied during engine operation by the relatively new technology of variable valve timing. It is also affected by the adjustment of the valve mechanism, and particularly by the tappet clearance; This variation is normally unwanted.

Many two-stroke cycle and all wankel engines do not have a camshaft or valves, and the port timing can only be varied by machining the ports. Some supercharged two-stroke diesel engines do however have a cylinder head and camshaft similar to a four-stroke cycle engine.

In a steam engine, the control of the valve timing is an important part of the operation of the engine. See valve gear, and also Walschaert valve gear, Berry accelerator valve gear, Baker valve gear, Woolf valve gear, Caprotti valve gear, Corliss valve gear.

Saab Variable Compression engine

The Saab Variable Compression engine was a development project of Saab Automobile, for which it won an award both in 2000 and 2001.

In a normal internal combustion engine, because cylinder bore diameter, piston stroke length and combustion chamber volume are almost always constant, the compression ratio (CR) for a given engine is almost always constant, until engine wear takes its toll.

One exception is the experimental Saab Variable Compression (SVC) engine, designed for the Saab 9-5. This engine uses a technique that dynamically alters the volume of the combustion chamber, thus changing the compression ratio.

To alter the combustion chamber volume, the SVC 'lowers' the cylinder head closer to the crankshaft. It does this by replacing the typical one-part engine block with a two-part block, with the crankshaft in the lower block and the cylinders in the upper portion. The two blocks are hinged together at one side. By pivoting the upper block around the hinge point, the volume of the combustion chamber can be modified. In practice, the SVC adjusts the upper block through a small range of motion, using a hydraulic actuator.

The SVC project was shelved by General Motors, when it took over Saab Automobile, due to cost.

Ten things that will increase the fuel economy of your vehicle

Ten things that will increase the fuel economy of your vehicle

Fuel prices surge upwards and show no sign of coming down, many people begin to wonder what can be done to save on fuel. there are a few things that can still be done to increase fuel economy. Here are ten things that you can do to save on fuel:

1. Filling up your tank properly.
This simply means try to avoid filling your tank to its maximum capacity. If the car becomes overheated, or if you are driving up a slope, then a tank which is filled to its maximum capacity will cause your fuel to drip onto the road where it can be dangerous (on rainy days, this will cause the road to be more slippery, and is a form of pollution).

On days where the temperature is high, try to fill your tank during the mornings or late afternoons where the temperature is cooler (since fuel will expand on hot days). This will allow you to have more fuel for your money, as well as preventing dangerous and costly run-off of wasted fuel.

2. Remove unnecessary weight from your car.
Did you know that for each 400 pounds that you carry in your car, this will mean 3-4 miles less that you can travel per gallon of fuel?

3. Amend your driving technique to increase fuel economy
• Drive at a conservative pace. If you vary your speed in anticipation of the road ahead you can save up to 25% of fuel. Make sure that any speed increases you make every time you press the accelerator are not cancelled out by having to slow down for a car in front of you, traffic light, or stop sign.

• Try to avoid making complete stops. By reducing your speed, rather than making a complete stop in anticipation of the traffic conditions ahead, you will be able to both conserve fuel as well as braking power.

• Start up slowly. When starting up from a complete stop, try to accelerate slowly. Accelerating at a conservative pace will carry you twice as much distance as racing ahead.

• Increase speed when approaching a hill. The temporary increase in speed will mean more momentum to push the car partially up the hill.

• Use downward momentum to your advantage. Rather than using the accelerator, use the downward momentum of your car to carry your vehicle further. However, only do this if it is safe to do so.

• Avoid having to change lanes frequently. When changing lanes, often you will need to accelerate to pass the car in front of you, and then use the slow down once you return to the lane. If done frequently, this can decrease fuel economy by up to 20-30%.

4. Use the air vents instead of windows.
Driving with open windows increase the drag on your car due to wind. This means the car will have to expend more power in order to move forward, and thus resulting in increased fuel consumption. Also avoid using the air conditioner if possible as this will also mean more fuel consumed.

5. Avoid warming up your car excessively.
Warming up your car in the morning means that you are using fuel to travel a grand total of 0 miles, and in the meantime also unnecessarily polluting the air around you.

6. Purchase a Hybrid vehicle.
Hybrid cars can clock upwards of 55 miles per gallon. This can often mean you will be able to increase fuel economy, and a possible monetary saving of around 25% - 35%.

7. Ensure that your tires are properly inflated.
Flat tires are a sure way to waste fuel as they can reduce the distance covered per gallon by as much as one mile.

8. Reduce wind resistance of your car.
A great way to do this is to make sure your car is waxed. This will allow wind to glide over your car easily, and thus reduce the drag on your vehicle.

9. Avoid using your car unnecessarily.
Driving with a cold engine can increase the amount of fuel consumed by as much as 60-70%, so try to make every trip count. In addition, by planning your trips, you may be able to cut down on the distance you will need to cover to do your shopping, get to work etc. Car pools are a great way to save on fuel going to work everyday.

10. Maintain your car regularly
The combined effects of the below suggestions will have a huge impact on the fuel economy of your car over time.

• Tune up your car regularly (especially the ignition system). A good tune-up by a qualified mechanic will save you fuel and extend the life of your vehicle.

• Make sure that the spark plugs are working properly (and that they are not misfiring). Misfiring spark plugs can possibly cost you 20% in mpg.

• Change dirty air filters (save 1 mph).

• Ensure your PCV valve is working appropriately.

• IMPORTANT: It is paramount that brakes are adjusted properly so that they do not drag along the wheel when your car is in motion. If your they are dragging along the wheel, then the car will demand more power when you are driving (to overcome the force of the brake). This can have major consequences in terms of fuel economy. To check that this is not happening to your car, jack up the tires and try to spin the wheel. If there is drag, then you will be able to feel it with your hand as you try to move the wheel.

Fuel saving devices

Since the development of the internal combustion engine, people have looked for ways to increase its efficiency, in order to increase the fuel economy of the automobile.

Although many technologies have had a beneficial effect on vehicles' fuel economies, claims as to the efficacy of some devices have clearly been bogus or misleading.

An early example of a "fuel saving gadget" sold with claims that were difficult to justify is the 200 mpg carburettor designed by Canadian inventor Charles Nelson Pogue

A good thing to keep in mind when examining fuel saving devices is that most of these claim major increases in combustion efficiency, something that sounds attractive when you consider the average gasoline engine rarely exceeds 35% efficiency. However, the weak point of the engine is not converting the fuel into heat, but the heat into mechanical energy, hence the reason why many fuel saving devices don't work as claimed. On modern engines there is relatively little scope for improving combustion efficiency. Most of what can be legitimately achieved is done by reducing parasitic losses of accessories e.g. fans, water pump, and pumping losses by taller vehicle gearing.

One reason that ineffective fuel saving gadgets have had some success in the marketplace is that it is surprisingly difficult to measure the fuel economy of a vehicle. This is because of the high level of variance in the fuel economy of a vehicle under normal driving conditions. Consequently, it is extremely difficult to measure small changes to fuel economy.

The large degree of fuel economy variance means that due to psychological factors of selective perception, consumers can be mislead as to the effectiveness of a device.

For this reason, regulatory bodies have developed standardised drive cycles that are useful for statistically significant comparisons of fuel economy


Vehicle Design Technologies

It is both easier and far more cost effective to design a vehicle to be fuel efficient than to modify an existing vehicle to improve its fuel economy.

Some effective technologies that can improve the fuel economy of a internal combustion engine vehicle include Fuel injection, Continuously variable transmission, Electrical motor assistance (known as hybrid vehicles), variable displacement, technologies to reduce vehicle weight, various friction reducing measures, and vehicle shell designs that reduce aerodynamic resistance (this doesn't improve engine efficiency, but reduces engine power needed to overcome drag, and consequently fuel consumption).

A more comprehensive list can be found in the category Engine technology


Retrofit devices

There are many devices currently being sold as "fuel saving devices" that have negligible or even harmful effects on fuel economy. The US environmental protection agency has issued reports on a number of aftermarket devices that claim to improve fuel economy

Some of these devices include:


Fuel additives

Materials which are added to the fuel include tin, magnesium and platinum compounds. The claimed purpose of these devices is generally to improve the energy density of the fuel by virtue of the materials added. Acetone is another additive, but may dissolve plastic parts in the fuel system.

These should not be confused with fuel system and valve cleaner additives which remove contaminants from the fuel system and/or remove deposits on intake valves.

Magnets attached to fuel lines have been claimed to improve fuel economy by aligning fuel molecules.


Vapour transfer devices

Various devices claim to improve fuel efficiency by changing the way that liquid fuel converts to fuel vapour. These include "Swirlers" to increase turbulence in the intake manifold and heaters



Friction reducing measures

Reducing friction is undoubtedly a powerful tool in reducing fuel consumption. Hardened silica tyres have lower rolling resistance than standard rubber tyres.

The typical lubricating oil used in engines has decreased in viscosity over the years. However, using a lubricant with lower viscosity than the lubricant specified by a vehicle manufacturer may damage an engine.

Air start system

The air start system on a large slow speed diesel engine is used to initiate ignition and consists of the following components: a compressor, an air reservoir (large cylindrical tank), associated piping, a control valve (this is linked to the camshaft), and the air start valves.

When starting the engine, compressed air is admitted to whichever cylinder has a piston just over top dead center, forcing it downward. As the engine starts to turn the air start valve on the next cylinder in line opens to continue the rotation. As this goes on, fuel is injected into the cylinders, the engine is then under way and the air is cut off.

To further complicate matters, a large engine is usually "blown over" first with zero fuel settings and the indicator cocks open, to prove that the engine is clear of any water build up and that everything is free to turn. After a successful blow ahead and a blow astern, the indicator cocks are closed on all the cylinders, and then the engine can be started on fuel.

Compared to a gasoline (petrol) engine, diesels have very high compression ratios to provide for reliable and complete ignition of the fuel without spark plugs. An electric starter powerful enough to turn a large diesel engine would itself be so large as to be impractical, thus the need for an alternative system.

Hydrogen fuel injection

Hydrogen Fuel Injection, or HFI, is a system to reduce exhaust emissions of internal combustion engines and improve fuel economy. HFI systems work by injecting hydrogen as a combustion enhancement into the intake manifold of an internal combustion engine to achieve these benefits. A small amount of hydrogen added to the intake air-fuel charge enhances the flame velocity and thus permits the engine to operate with leaner air-to-fuel mixture than otherwise possible. The result is lower pollution with more power and better mileage.

A simplified single-step combustion reaction is represented as: [FUEL] + [HYDROGEN] + [AIR] -> HC + CO + CO2 + H2O + NOx

For incomplete combustion, the above results in exhaust products including unburned hydrocarbons (HC) and carbon monoxide (CO). The NOx is formed mainly from the combustion air, and is highly temperature-dependent.

In 1974 John Houseman and D.J Cerini of the Jet Propulsion Laboratory, California Institute of Technology produced a report for the Society of Automotive Engineers entitled "On-Board Hydrogen Generator for a Partial Hydrogen Injection Internal Combustion Engine". In the same year, F.W. Hoehn and M.W. Dowy, also of the Jet Propulsion Lab, prepared a report for the 9th Intersociety Energy Conversion Engineering Conference, entitled "Feasibility Demonstration of a Road Vehicle Fueled with Hydrogen Enriched Gasoline." This research utilized onboard storage tanks to supply the hydrogen combustion enhancement.

More recent investigations have highlighted the potential for pollutant reduction. Research performed by scientists at the University of Birmingham, United Kingdom, released a study in June of 1995 at the HYPOTHESIS Conference at the University of Cassino, Italy in which it was presented that "hydrogen, when used as a fractional additive at extreme lean engine operation, yields benefits in improved combustion stability and reduced nitrogen oxides and hydrocarbon emissions." Similar results have been presented by a team of scientists representing the Department of Energy Engineering, Zhejiang University, China in the Spring of 1997 at an international conference held by the University of Calgary. Practical tests have been performed by California Environmental Engineering (CEE), The American Hydrogen Association Test Lab and Corrections Canada in which reduction in toxic exhaust emissions and fuel consumption were realized.

Commercially, Canadian Hydrogen Energy Company, LTD, produces an HFI system which generates hydrogen during vehicle operation by electrolyzing water (from an onboard storage tank) using power from the vehicle's electrical system. In dynamometer tests with 1992 60 series diesel engine fueled by low-sulphur (<15 PPM) diesel fuel, the system draws a maximum of 35 amps (12V DC) and yields 4.44% reduced fuel consumption, 6.17% reduced HC emissions, 0.39% reduces CO emissions, 4.34% reduced NOx emissions, and 7.0% reduced PM (particulate matter) emissions.

Publicly, Canadian Eagle Research Company produces the HyZor on-board electrolyzer that is comparable to coexisting commercial devices primarily being scaled down to fit Sedans, Coupes, SUV's, and Hybrids. A unique feature of the system is its design not to remove oxygen giving the output gas properties extremely similar to the HFI system while eliminating the required ducting components necessary to separate oxygen. These systems are fully automated only requiring occasional refills of distilled water when the system informs the driver by dash mounted led’s controlled by an electronic circuit integrated with the vehicles ignition.

Capacitor discharge ignition

Capacitor discharge ignition (CDI) is a type of automotive electronic ignition system which is widely used in motorcycles, lawn mowers, chain saws, small engines and recently in some cars. Capacitor discharge ignition uses capacitor discharge current output to fire the spark plugs.


The basic principle

Most of typical ignition system used in cars are inductive ignition system, which is solely relying on the electric inductance at the coil to produce high-voltage electricity to the spark plugs. In a CDI system, the system charges a capacitor by default, and during the ignition point the system stopps charging the capacitor, allowing the capacitor to discharge its output to the final coil before reaching the spark plug.

A typical CDI module may consist of a small transformer, a charging circuit, a triggering circuit and a main capacitor. Firstly, the system voltage is raised up to 400 V by a transformer inside the CDI module. Then, the electric current flows to the charging circuit and charges the capacitor. The rectifier inside the charging circuit prevents capacitor discharge before the ignition point.

When the triggering circuit receives triggering signals from triggering devices such as Hall effect sensor or pulse generator during the ignition point, the triggering circuit stops the operation of the charging circuit, allowing the capacitor to discharge its output rapidly to the ignition coil. The rapid capacitor discharge then produces a very high voltage at about 40 kV to be fired at the spark plug. When there's no triggering signal, the charging circuit is re-connected to charge back the capacitor.


CDI modules can be generally divided into two:-

* AC-CDI - The AC-CDI module obtains its electricity source solely from the alternating current produced by the alternator. The AC-CDI system is the most basic CDI system which is widely used in small engines.
* DC-CDI - The DC-CDI module is powered by the battery, and therefore an additional DC/DC inverter circuit is included in the CDI module to raise the 12 V DC to 400 V DC, making the CDI module slightly larger. However, the vehicle that uses DC-CDI system has more precise ignition timing and the engine can be started easier when cold.


Advantages and Disadvantages of CDI

CDI system produces higher ignition voltage (about 40 kV) compared with typical inductive ignition system (about 20 kV). The higher voltage produced by the CDI system produces a hotter spark, enabling the engine to be operated even with badly-fouled spark plugs.

The CDI system also has a faster voltage rise time (between 3 ~ 10 kV/μs) compared with typical inductive systems (300 ~ 500 V/μs). The higher voltage rise time results in a shorter spark duration with the CDI system (10 ~ 12 μs) and therefore the spark output is more accurate.

However, the shorter spark duration means the CDI system is not suitable for sharing between cylinders in multi-cylinder engines. It was not until the end of the 1990s that CDI system could be practically used in multi-cylinder engines, especially in cars, as a result of the development of the direct ignition system, where each cylinder has its own ignition coil.

CDI systems also have problems with lean air-fuel mixture and high compression engines as well as cold-starting problems. However, the problems can be solved by using waste-spark methods.


History

THe history of capacitor discharge ignition system can be traced back in 1950s together with the development of other electronic ignition systems. The first commercial motorcycle using the CDI system was manufactured by Kawasaki.

By the end of 1960s, the US government made new laws enforcing strict emission standards. As a result, more and more electronic ignition systems were developed, and starting from 1970s all smaller engines installed CDI system to replace the contact point system, including Honda Cub which began to use AC-CDI system.

By the end of 1990s, direct ignition system using capacitor discharge ignition system was developed and started to be installed on some newer car models.

Hypereutectic piston

“Hypereutectic” means “Over” eutectic. The word eutectic refers to a condition in chemistry when two elements can be alloyed together on a molecular level, but only up to a specific percentage, at which point any additional secondary element will retain a distinct separate form.

Although internal combustion engine pistons commonly contain trace amounts (less than 2% each) of Copper, Manganese, and Nickel, the major element in automotive pistons is Aluminum due to its light weight, low cost, and acceptable strength. The alloying element of concern in automotive pistons is Silicon. Gold and Silver have no eutectic point, which means they can be alloyed together in any ratio. However, when Silicon is added to Aluminum they will only blend together evenly on a molecular level up to approximately a 12% Silicon content. For the purposes of this discussion, Silicon in this context can be thought of as “powdered sand”, and any Silicon that is added to aluminum at above a 12% content will retain a distinct granular form instead of melting. At a blend of 25% Silicon, there is a significant reduction of strength in the piston alloy, so stock hypereutectic pistons commonly use a level of Silicon between 16% and 19%. Special molds, casting, and cooling techniques are required to obtain uniformly dispersed silicon particles throughout the piston material.


The reason for their development

Most automotive engines use aluminum pistons that cycle in a steel cylinder. The average temperature of a piston crown in a gasoline engine during normal operation is typically about 600 degrees Fahrenheit, and the coolant that runs through the engine block is usually regulated at approximately 190 degrees F. Aluminum expands more than steel at this temperature range, so for the piston to fit the cylinder properly when at a normal operating temperature, the piston must have a loose fit when cold.

In the 1970’s, increasing concern over exhaust pollution caused the U.S. government to form the Environmental Protection Agency (EPA) which began passing legislation that forced auto manufacturers to make changes that allowed their engines to run cleaner. By the late 1980’s, auto exhaust pollution had been noticeably improved, but increasingly stringent regulations forced car manufacturers to adopt the use of electronically controlled fuel injection and hypereutectic pistons. It was discovered that when an engine is cold, a small amount of excess fuel during start-up became trapped between the piston rings. This admittedly small quantity of excess fuel affected the amount of hydrocarbons in the exhaust when the piston expanded as it warmed, and then expelled the excess fuel.

By adding Silicon to the pistons alloy, the amount the piston expanded could be dramatically reduced, which allowed engineers to specify a much tighter cold-fit. Silicon itself expands less than Aluminum, and it also acts as an insulator to prevent the Aluminum from absorbing as much of the operational heat as it otherwise would. Another beneficial effect of adding Silicon is that the piston becomes harder, and is less susceptible to scuffing, which can occur when a soft aluminum piston is cold-revved in a relatively dry cylinder on start-up.

The biggest drawback of piston Silicon is that the piston becomes more brittle as more Silicon is added, which allows the piston to develop cracks easier if the engine experiences pre-ignition or detonation.


Performance replacement alloys

When an auto enthusiast wants to increase the power of their engine, they often add some type of forced induction. By compressing more air and fuel into each intake cycle, the power of the engine can be dramatically increased. This also increases the heat and pressure in the cylinder.

The normal temperature of gasoline engine exhaust is approximately 1200 F. This is also approximately the melting point of most Aluminum alloys, and it is only the constant influx of ambient air that prevents the piston from deforming and failing due to excess temperatures. Forced induction increases the operating temperatures while “under boost”, and if the excess heat is added faster than engine can shed it, the elevated cylinder temperatures will cause the air and fuel mix to auto-ignite on the compression stroke before the spark event. This is one type of engine knocking that causes a sudden shock wave and pressure spike, which can result in an immediate and catastrophic failure of the piston and connecting rod.

The “4032” performance piston alloy has an approximate Silicon content of 11%. This means that it expands from heat less than a piston with no Silicon, but since its eutectic level of Silicon is fully alloyed on a molecular level, this alloy is less brittle and more flexible than a stock Hypereutectic “smog” piston. These pistons can survive mild detonation with less damage than stock pistons.

The “2618” performance piston alloy has less than 2% Silicon and could be described as Hypo (under) eutectic. This alloy is capable of experiencing the most detonation and abuse while suffering the least amount of damage. Pistons made of this alloy are also typically made thicker and heavier because of their most common applications. Because of the higher than normal temperatures these pistons experience in their usual application, and also the low-Silicon content allowing the maximum possible Aluminum heat-expansion, these pistons have their cylinders bored to a very loose cold-fit. This leads to a condition known as “piston slap” which is when the piston rocks in the cylinder, and it causes an audible tapping noise that continues until the engine has warmed to operational temperatures. These engines should not be revved when cold, or excessive scuffing can occur.


Forged versus Cast

When a piston is cast, the alloy is heated until it is a liquid, and then it is poured into a mold to create its basic shape. After the alloy cools and solidifies, it is removed from the mold, and then the rough casting is machined to its final shape. When a piston is desired that is stronger than what simple casting can provide, they can be forged. This is when the rough casting is placed in a die set while it is still hot, and a hydraulic press is used to place the rough slug under a tremendous amount of pressure. This removes any possible porosity and also pushes the alloy grains together tighter than what can be achieved by simple casting alone, resulting in a much stronger material.

Hypereutectic pistons can be forged, but typically are only cast. This is because cast pistons are considered strong enough for stock applications, and the extra expense is not justified.

Aftermarket performance pistons made from the most common 4032 and 2618 alloys that are often used to replace stock hypereutectic pistons are typically forged.

Hot tube engine

The hot tube engine is a relative of the hot bulb engine with better timing control. The hot bulb engine only ran well at one speed- and a low one at that, typically 100 RPM. The timing of a hot tube engine is controlled by means of varying the length of the Hot-tube ignitor, which is longer and thinner than the hot bulb on a hot bulb engine. Length of the tube controls when the charge ignites, and allows different operating speeds to be selected. If made variable, this makes for adjustable engine speed, but also induces a mechanical weakness in the engine which tends to lead to failure. Both engine types are now replaced by diesels, which can be made to operate over varying loads and speeds in any size with modern methods. Hot bulbs are still used in remote areas where the extreme fuel flexibility is a major advantage. Hot tube engines may also be found there, if their difficulties with the adjustable tube can be overcome, or accepted and lived with.

Alcohol fuel

Rising energy prices and global warming have led to increased interest in alternative fuels. Alcohol has been used as a fuel in other points in history but fossil fuels have become the dominant energy resource for the modern world. Generally speaking, the chemical formula for alcohol fuel is CnH2n+2O. The larger n is, the higher the energy density.

The first four aliphatic alcohols (methanol, ethanol, propanol, and butanol) are of interest as fuels because they can be synthesized biologically, and they have characteristics which allow them to be used in current engines. One advantage shared by all four alcohols is octane rating. Biobutanol has the advantage that its energy density is closer to gasoline than the other alcohols (while still retaining over 25% higher octane rating).

Alcohol fuels are usually of biological rather than petroleum sources. When obtained from biological sources, they are sometimes known as bioalcohols (e.g. bioethanol). It is important to note that there is no chemical difference between biologically produced alcohols and those obtained from other sources. However, ethanol that is derived from petroleum should not be considered safe for consumption as this alcohol contains about 5% methanol and may cause blindness or death. This mixture may also not be purified by simple distillation, as it forms an azeotropic mixture.

Bioalcohols are still in developmental and research stages. Use of optimized crops with higher yields of energy, elimination of pesticides and fertilizers based on petroleum, and a more rigorous accounting process will help improve the feasibility of bioalcohols as fuels.

Forced induction

Forced induction is a term used to describe internal combustion engines that are not naturally aspirated. Instead, a gas compressor is added to the air intake, thereby increasing the quantity of oxygen available for combustion. This compressed air is normally referred to as Boost or charge air.


Introduction

Forced induction can be used to increase the power of an engine or its efficiency, or both, without much extra weight. The ambient air that the engine is normally ingesting enters the compressor inlet of turbocharger or supercharger that is inline along the air intake tract. This effectively increases the pressure and density of the air, which allows for a much greater percentage of oxygen per volume of air intake to be added to the air/fuel mixture. The effects are an increase to the effective capacity of the engine without an increase in physical size. The forced induction approach has the advantage that the intake pressure may be regulated according to the engine speed, thus providing power from extra capacity at high speed, but without wasting fuel at lower speeds. A Nitrous Oxide system is also a form of forced induction. A simple oxidizer is injected either directly (direct port) or by a single fogger...with fuel(wet nitrous system) or without fuel(dry nitrous system).

Two of the commonly used forced induction technologies are turbochargers and superchargers. They differ mainly in the power source for the compressor. Turbochargers are driven by the exhaust gases of the engine, whereas superchargers are driven by a geartrain or belt connected to the crankshaft of the engine.


Comparison

Strengths and weaknesses vary according to the method of forcing induction largely based upon the inherent design functions of both. A turbocharger acts as an obstacle to exhaust gases due to its placement in the exhaust system tract. A supercharger uses torque generated from the rotational mass internal to the engine through the crank pulley. A turbo relies on the volume and velocity of exhaust gases to spool, or spin the turbine wheel. The turbine wheel is connected to the compressor wheel via a common shaft. The compressor wheel compresses the intake charge increasing the charge density by a large factor. The amount of time that it takes a turbocharger to reach the onset of boost is referred to as lag. A supercharger is 'on' all of the time, meaning that it is capable of producing a linear increase of boost up until redline. It is easier to target a desired boost with a turbocharger as there are many forms of boost controllers that allow a user to adjust to desired boost fairly easily. In order to achieve desired boost with a supercharger, a larger or smaller pulley must be installed.


Intercooling

A fundamental principle to forced induction is that compressing air raises its temperature. As a result, the charge density is reduced and the cylinders receive less fresh air than the system’s boost pressure prescribes. The risk of pre-ignition or "knock" in internal combustion engines greatly increases. These drawbacks are countered by charge-air cooling, which passes the air leaving the turbocharger or supercharger through a heat exchanger typically called an intercooler. This is done by cooling the charge air with an ambient flow of either air (air-air intercoolers) or liquid (liquid to air intercoolers), the charge air density is increased and the temperature is reduced.


Alcohol/Water Injection

Additionally, alcohol injection is an effective means of cooling the charge air. Methanol is the preferred alcohol due to its elemental properties, and is normally mixed with water to prevent evaporation. Methanol is typically injected pre throttle body. Methanol, unlike nitrous oxide or forced induction itself, doesn't add more oxygen to the charge, but by its low evaporation point changes from a liquid to a gas as its introduced into the air charge. The evaporation process uses the heat from the intake charge to complete the phase change. The alcohol is also a fuel in the charge which will cause a rich condition if used in excess. Due to the lower intake temperatures and denser air charge more power is exerted from the engine. Methanol is typically used in conjunction with poor quality fuel(pump gas) in order to run higher than normal boost pressures.

Like was stated above, adding forced induction increases the amount of air an engine can use for combustion, in effect allowing more fuel to be used with the available oxygen. Further, it increases an engine's dynamic compression ratio. As compression ratio increases, so does the threat of knock and therefore the need for higher octane fuel.

Hybrid Synergy Drive

Hybrid Synergy Drive, (HSD) is a set of hybrid car technologies developed by Toyota and used in that company's Prius, Highlander Hybrid, Camry Hybrid, Lexus RX 400h, and Lexus GS 450h automobiles. In 2008, the Corolla will also have a HSD hybrid version. It combines the characteristics of an electric drive and a continuously variable transmission, using electricity and transistors in place of toothed gears. The Synergy Drive is a drive-by-wire system with no direct mechanical connection between the engine and the engine controls: both the gas pedal and the gearshift lever in an HSD car merely send electrical signals to a control computer.

HSD is a refinement of the original Toyota Hybrid System (THS) used in the 1997–2003 Toyota Prius. As such it is occasionally referred to as THS II. The name was changed in anticipation of its use in vehicles outside the Toyota brand (Lexus; the HSD systems used in Lexus vehicles have since been termed Lexus Hybrid Drive since 2006).

When required to classify the transmission type of an HSD vehicle (such as in standard specification lists or for regulatory purposes), Toyota describes HSD-equipped vehicles as having E-CVT (Electronically-controlled Continuously Variable Transmission).

General Motors and DaimlerChrysler's Global Hybrid Cooperation is similar in that it combines the power from a single engine and two motors. In contrast, Honda's Integrated Motor Assist uses a more traditional ICE and transmission where the flywheel is replaced with an electric motor.

Some early non-production Plug-in hybrid electric vehicle conversions have been based on the version of HSD found in the 2004 and 2005 model year Prius. Early Pba conversions by CalCars have demonstrated 10 miles of ev-only and 20 miles of double mileage mixed-mode range. A company planning to offer conversions to consumers named EDrive systems will be using Valence Li-ion batteries and have 35 miles of electric range. Both of these systems leave the existing HSD system mostly unchanged and could be similarly applied to other hybrid powertrain flavors by simply replacing the stock NiMH batteries with a higher capacity battery pack and of course a charger to refill them for about $0.03 per mile from standard household outlets. Another provider of a plug-in module for the Toyota Prius is Hymotion.



Phases of operation

The HSD operates in distinct phases depending on speed and demanded torque. Here are a few of them:

* Engine start: The vehicle launch is done in all-electric mode. The engine starts once a limiting speed in the generator is reached. At the engine cut-in point, MG1 is fed negative voltage, so that it acts as a starter motor. The engine is forced into forward motion. Because both motor generators are sized to drive the entire car, turning the engine does not stress the motors and the conventional starter motor sound is not heard: engine start is silent.

* Low gear (equivalent): When accelerating at low speeds in normal operation, the engine turns much more rapidly than the wheels, but does not develop as much torque as is needed. MG1 is forced rapidly backwards, and the computer pulls electricity from MG1. The electricity is shunted to MG2, adding torque at the driveshaft, so that the drive train develops power at low speed and high torque.

* High gear (equivalent): When cruising at high speed, the engine turns more slowly than the wheels, but develops more torque than is needed. The computer pulls electricity from MG2, reducing the torque available at the wheels. The electricity is shunted to MG1, which boosts the speed of the driveshaft. Because the engine supplies mechanical energy to the whole system, conservation of energy is not violated: the power that is shunted from MG2 to MG1 is less than the total power developed by the engine, and so power is delivered to the wheels.

* Reverse gear: There is no reverse gear as in a conventional gearbox: the computer feeds negative voltage to MG2, applying negative torque to the wheels. Early models did not supply enough torque for some situations: there have been reports of early Prius owners not being able to back the car up steep hills in San Francisco. The problem has been fixed in recent models. If the battery is low, the system can simultaneously run the engine and draw power from MG1, although this will reduce available reverse torque at the wheels.

* Silent operation: At slow speeds and moderate torques the HSD can drive without running the gasoline engine at all: electricity is supplied only to MG2, allowing MG1 to rotate freely (and thus decoupling the engine from the wheels). This is popularly known as "Stealth Mode." Provided that there is enough battery power, the car can be driven in this silent mode for some miles even without gasoline.

* Neutral gear: Most jurisdictions require automotive transmissions to have a neutral gear that decouples the engine and transmission. The HSD "neutral gear" is achieved by breaking the electrical connection to both MG1 and MG2. Under this condition, MG1 is free running and no torque can be delivered to the wheels (MG1 rotates backwards when the engine rotates forward).

* Regenerative braking: by drawing power from MG2 and depositing it into the battery pack, the HSD can simulate normal compression braking while saving the power for future boost. The HSD system has a special transmission setting labelled 'B' (for Brake), that takes the place of a conventional automatic transmission's 'L' setting for engine braking on hills. If the battery is full, the system switches to conventional compression braking, drawing power from MG2 and shunting it to MG1 to slow the speed of the engine. The regenerative brakes in a HSD system absorb a significant amount of the normal braking load, so the conventional brakes on HSD vehicles are undersized compared to brakes on a conventional car of similar mass.

* Electric boost: The battery pack provides a reservoir of energy that allows the computer to match the demand on the engine to a predetermined optimal load curve, rather than operating at the torque and speed demanded by the driver and road. The computer manages the energy level stored in the battery, so as to have capacity to absorb extra energy where needed or supply extra energy to boost engine power.

* Battery charging: The HSD can charge its battery without moving the car, by running the engine and extracting electrical power from MG1. The power gets shunted into the battery, and no torque is supplied to the wheels.




Performance

The Toyota Prius has decent, but not sport-car-like, acceleration but has extremely high mileage for a mid sized four-door sedan: 45 mpg (US) is typical of brief city jaunts; 55 mpg is not uncommon, especially for extended drives (which allow the engine to warm up fully). This is about twice the fuel efficiency of a similarly equipped four-door sedan with a conventional power train. Not all of the extra efficiency of the Prius is due to the HSD system: the Atkinson cycle engine itself was also designed specifically to minimize engine drag with an offset crankshaft to minimize piston drag during the power stroke, and a unique intake system to prevent drag caused by manifold vacuum versus the normal Otto cycle in most engines.

The Highlander Hybrid (also sold as the Kluger in some countries) offers better performance compared to its non-hybrid version. The hybrid version goes from 0–60 mph in 7.2 seconds, trimming almost a second off the conventional version's time. Net hp is 268 hp compared with to the conventional 215 hp. Top speed for all Highlanders are limited to 112 mph. Typical fuel economy for the Highlander rates between 27 and 31 mpg. A conventional Highlander is rated by the EPA with 19 city, 25 highway mpg.

Ford Motor Company licensed HSD technology in 2004 and it is currently offered in an SUV, the Ford Escape, though a hybrid Ford Fusion will be released in the future. The four-cylinder hybrid Escape achieves an impressive increase in mileage, to 28–32 mpg.

There have been reports in the press of hybrid power trains not living up to fuel efficiency claims. This is due in part to the sensitivity of hybrid mileage to driving style. The mileage boost depends on using the gasoline engine as efficiently as possible, which requires:

* extended drives, especially in winter: Heating the internal cabin for the passengers runs counter to the design of the HSD. The HSD is designed to generate as little waste heat as possible. In a conventional car, this waste heat in winter is usually used to heat the internal cabin. In the Prius, running the heater will the require the engine to continue running to generate cabin-usable heat. This effect is most pronounced by turning the climate control (heater) off when at a stop when the engine is running. Normally the HSD control system will shut the engine off as it is not needed, and will not start it again until the generator reaches a maximum speed.

* moderate acceleration: Because hybrid cars can throttle back or completely shut off the engine during moderate, but not rapid, acceleration, they are more sensitive than conventional cars to driving style. Hard acceleration forces the engine into a high-power state while moderate acceleration keeps the engine in a lower power, high efficiency state (augmented by battery boost).

* gradual braking: Regenerative brakes re-use the energy of braking, but cannot absorb energy as fast as conventional brakes. Gradual braking recovers energy for re-use, boosting mileage; hard braking wastes the energy as heat, just as for a conventional car

Most HSD systems have batteries that are sized for maximal boost during a single acceleration from zero to the top speed of the vehicle; if there is more demand, the battery can be completely exhausted, so that this extra torque boost is not available. Then the system reverts to just the power available from the engine. This is a big difference in performance: an early-model Prius can achieve over 90 mph on a 6 degree upward slope, but after about 2,000 feet of altitude climb the battery is exhausted and the car can only achieve 55–60 mph on the same slope (until the battery is recharged by driving under less demanding circumstances).

Short Long Arms Suspension

An SLA is also known as an unequal length double wishbone suspension. The upper arm is typically an A-arm, and is shorter than the lower link, which is an A-arm or an L-arm, or sometimes a pair of tension/compression arms. In the latter case the suspension can be called a multi-link, or Dual ball joint suspension.

The four bar link mechanism formed by the unequal arm lengths causes a change in the camber of the vehicle as it rolls, which helps to keep the contact patch square on the ground, increasing the ultimate cornering capacity of the vehicle. It also reduces the wear of the outer edge of the tire.

SLAs can be classified as short spindle, in which the upper ball joint on the spindle is inside the wheel, or long spindle, in which the spindle tucks around the tire and the upper ball joint sits above the tire.

Double wishbone suspension

In automobiles, a double wishbone (or "upper and lower A-arm") suspension is an independent suspension design using two parallel wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting positions to the chassis and one joint at the knuckle. The shock absorber and coil spring mount to the wishbones to control vertical movement. Double wishbone designs allow the engineer to carefully control the motion of the wheel throughout suspension travel, controlling such parameters as camber angle, caster angle, toe pattern, roll center height, scrub radius, scuff and more.

The double wishbone suspension is also often referred to as double 'A' arm or short long arm (SLA) suspension. It is commonly used in sports cars, luxury cars and light trucks.

A single wishbones or A-arms are used in various other suspension types, such as MacPherson strut and Chapman strut.

The suspension consists of a pair of upper and lower lateral arms, roughly horizontal and of similar length. The upper arm is usually slightly shorter to induce more negative camber on the outside wheel as the vehicle body rolls in a turn. Between the arms there is a knuckle with a spindle or hub which carries the wheel bearing and wheel. Knuckles with an integral spindle usually do not allow the wheel to be driven. A bolt on hub design is commonly used if the wheel is to be driven.

In order to resist fore-aft loads such as acceleration and braking, the arms need two bushings or ball joints at the body.

At the knuckle end, single ball joints can be used, in which case the steering loads have to be taken via a steering arm, and the wishbones look A- or L-shaped. An L-shaped arm is generally preferred on passenger vehicles because it allows a better compromise of handling and comfort to be tuned in. The bushing in line with the wheel can be kept relatively stiff to effectively handle cornering loads while the offline joint can be softer to allow the wheel to recess under fore aft impact loads. For a rear suspension, a pair of joints can be used at both ends of the arm, making them more H-shaped in plain view.

In front view, the suspension is a 4-bar link, and it is easy to work out the camber gain (see camber angle) and other parameters for a given set of bush locations.

The various bushes do not have to be on horizontal axes, parallel to the vehicle centre line. If they are set at an angle, then antidive and antisquat can be dialled in.

The advantage of a double wishbone suspension is that it is fairly easy to work out the effect of moving each joint, so you can tune the kinematics of the suspension easily and optimize wheel motion. It is also easy to work out the loads that different parts will be subjected to which allows more optimized lightweight parts to be designed.

The disadvantage is that it is slightly more complex than other systems like a MacPherson strut.

SLAs are very common on front suspensions for larger cars, Pickups and SUV's and double wishbones are very common at both ends of racing cars.

Prior to the dominance of front wheel drive in the 1980s, many everyday cars used double wishbone front suspension systems, or a variation on it. Since that time, the MacPherson strut has become almost ubiquitous, as it is simpler and cheaper to manufacture. Double wishbones are usually considered to have superior dynamic characteristics, load handling capability and are still found on higher performance vehicles.

Ferrari FXX

The Ferrari FXX is a car developed as part of an unusual development program by automobile manufacturer Ferrari in Maranello, Italy. It began production in 2005.

The car uses some technology developed from the Enzo Ferrari and combines it with some all-new developments from Ferrari and some of the suppliers. However, the car is only a part of the overall program: people pay £1.3 million ($2 million usd) but are only allowed to drive the car on special track days approved by Ferrari and after they drive the car they have to brief Ferrari on the car's performance. Michael Schumacher was given one when he retired from Formula One racing at the end of 2006. Ferrari's sister company, Maserati has developed a similar car, the MC12 Corsa.



The Car

Essentially an evolution of the Enzo, the FXX shares some components with its parent car, but significant portions are exclusive to the FXX.

The FXX's engine is based on the Enzo's but has been expanded to 6,262 cc (from 5,988 cc), and output has been boosted from 660PS, as seen in the Enzo, to 800PS (588kW) @ 8,500 rpm.

The gearbox incorporates the latest developments from Ferrari's F1 program and has a shift time under 100 ms. The brake pads are upgraded compared to those on the Enzo. It does, however, retain the ceramic discs found on the Enzo.

The tires on the FXX are 19 in (483 mm) slicks custom-developed for the car.

As with the Enzo, the seat and pedal configuration are custom fit to the user's exact measurements.

The FXX features a comprehensive data-monitoring and telemetry that not only allows the driver to improve performance, but also provides Ferrari technicians with valuable data to improve the FXX and future road-going Ferraris.

Ferrari has built 30 of these cars, and they have all been sold to preselected past Ferrari customers, including Ferrari's F1 World Champion driver, Michael Schumacher. Schumacher's FXX differs from others in that it is the only black FXX and comes with red trim on the rims, matte exhaust tips (regular FXX's have chrome tips), number 30 on the doors and his personal insignia on the seats. One car was not sold and is kept by Ferrari. These few customers will not only own a Ferrari FXX, but also participate in further testing and brand development. As the vehicle is not street-legal, owners have the option of storing the car at Ferrari's facilities. As part of the FXX program, the car is maintained by the Ferrari factory. The purpose of this particular program is to allow Ferrari's top customers exclusive access to its most up-to-date technology and to use their input to help develop future models. The FXX was reported to cost 1.5 million euro (excluding taxes)[1], for the car and the services that Ferrari provides with it.


Specifications

* Engine: Longitudinal, Mid-mounted, 75, naturally-aspirated aluminum V12

* Valvetrain: DOHC, 4 valves per cylinder with continuously variable timing

* Fuel system: Bosch Motronic ME7 Sequential Electronic Injection

* Specific Output: 127.75 PS (126 hp/94 kW) per litre

* Drive system: RWD w/TCS

* Construction: Carbon fiber body over carbon fiber tub with rear alloy subframe

* Front brakes: Brembo CCM (carbon-ceramic) discs w/6-pot calipers, power assist ABS

* Rear brakes: Brembo CCM (carbon-ceramic) discs w/4-pot calipers, power assist ABS

* Front wheels: 483 mm (19 in) x 229 mm (9 in)

* Rear wheels: 483 mm (19 in) x 330 mm (13 in)

* Steering: Rack and pinion with power assist

* Suspension: Double wishbones with push-rod actuated coil-shock units, adaptive dampers, electronic shock absorbers, anti-roll bar

* Wheelbase: 2650 mm (104 in)

* Front track: 1660 mm (65 in)

* Rear track: 1650 mm (65 in)

Pushrod engine

A pushrod engine or I-head engine is a type of piston engine that places the camshaft in the cylinder block (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine) and uses pushrods or rods to actuate rocker arms above the cylinder head to actuate the valves. Lifters or tappets reside in the engine block between the camshaft and pushrods.

This contrasts with an overhead cam (OHC) design which places the camshafts above the cylinder head and drives the valves directly or through short rocker arms. In an OHC engine, the camshafts are normally part of the cylinder head assembly, while in an I-head engine the camshaft (rarely more than one) is part of the main engine block assembly.

Pushrod engines are perceived to be "old fashioned" by the modern automotive press, the cause is historical: While both layouts are over 100 years old, the I-head engine came first. OHC engines were developed as more expensive high-performance engines and have largely replaced the pushrod design in countries where cars are taxed based on engine displacement. In 1949, Oldsmobile introduced the Rocket V8. It was the first high-compression I-head design, and is the archetype for most modern pushrod engines. General Motors is the world's largest pushrod engine producer with engines such as the 3800 Series III Supercharged V6 (260 hp, 280 lb/ft torque), LS7 Chevrolet Corvette 7.0L V8 Engine (505 hp, 475 lb/ft torque) and LS4 5.3L DOD V8 (303 hp, 323 ft·lbf torque). Fewer pushrod type engines remain in production, a result of the fact that it has become difficult to achieve competitive engine performance with the configuration. However, in 2002, Chrysler introduced a new pushrod engine: a 5.7L Hemi engine. The new Chrysler Hemi engine presents advanced features such as variable displacement technology and has been a popular option with buyers. The Hemi was on the Ward's 10 Best Engines list for 2003 through 2007.



Limitations

Three specific problems remain with pushrod engines:

* Limited engine speeds or rpm - Pushrod engines have more reciprocating mass, suffer more easily from valve "float", and exhibit a tendency for the pushrods themselves to flex or snap at high engine speeds. Therefore a pushrod engine cannot revolve ("rev") at engine speeds as high as an OHC design. Modern pushrod engines generally rev to 6,000 rpm: compare this to modern OHC engines that can easily rev from 7,000 rpm in average engines to near 20,000 rpm in Formula One racing engines. High-rev pushrod engines have also been developed — in 1969, Chevrolet offered a Camaro Z28 with a pushrod V8 that could rev to 8,000 rpm and the Volvo B18 and B20 engines can rev to more than 7,000 rpm. Various pushrod racing engines are capable of reaching from 9,000 in some series to 10,500 rpm in others.

Because overall power is computed by multiplying torque by revolution speed (HP = (RPM x LB-FT) / 5252), an engine capable of revving higher will produce more power from the same amount of torque than one revving lower. A pushrod engine therefore needs to have a larger displacement to match the power output of an OHC engine. A good comparison would be the 3.9L GM 3900 Engine to the 3.0L Honda J-series V6. The smaller (in displacement) Honda Engine produces more power, while requiring less torque to do so.

* Difficulty in using crossflow cylinder heads in straight engine configurations - A few straight pushrod engines have been manufactured with crossflow heads, such as the six cylinder Humber Super Snipe. These engines combined much of the performance of the overhead camshaft with the ease of service of the pushrod, but were more expensive to manufacture than either competing design.

* Limited design flexibility - The biggest benefit of an OHC design is the use of multiple intake and exhaust valves and variable valve timing. Most modern pushrod engines have two valves per cylinder, while many OHC engines use three, four or even five valves per cylinder to achieve greater efficiency and power. Recently, however, GM has begun offering a pushrod V6 with VVT, and Cummins' ISB is a 4-valve pushrod straight-6. For the 2006 model year, General Motors will introduce the Vortec 6200. This is the first mass-produced pushrod engine to feature variable valve timing. The system adjusts both intake and exhaust timing between two settings. There is even a company called Arao Engineering that has developed and patented a 32-valve aluminum cylinder head for various pushrod engines like the small/big block Chevrolet engines and Ford small/big block engines.


Advantages

In contrast, pushrod engines have two specific advantages:

* Smaller overall packaging - Because of the camshaft's location inside the engine block, pushrods are generally more compact than an overhead cam engine of comparable displacement. For example, Ford's 4.6 L OHC modular V8 is larger than the 5.0 L I-head Windsor V8 it replaced and GM's 4.6 L OHC Northstar V8 is slightly taller and wider than GM's larger displacement 5.7 to 7.0 L I-head LS V8. The Ford Ka uses the venerable Kent Crossflow pushrod engine to fit under its low bonnet line.

* Less complex drive system - Pushrod engines have a less complex drive system when compared with OHC engines. Most OHC engines drive the camshaft or camshafts using a timing belt, a chain or multiple chains. These systems require the use of tensioners which add some complexity to the engine.


1994 Mercedes Indianapolis 500 engine

The Indy 500 race in Indianapolis each year bears some vestige of its original purpose as a proving ground for automobile manufacturers, in that it once gave an advantage in engine displacement to engines based on stock production engines, as distinct from out-and-out racing engines designed from scratch. One factor in identifying production from racing engines was the use of pushrods, rather than the overhead cams used on most modern racing engines; Mercedes-Benz realized before the 1994 race that they could very carefully tailor a purpose-built racing engine using pushrods to meet the requirements of the Indy rules and take advantage of the 'production based' loophole but still design it to be state of the racing art in all other ways, without any of the drawbacks of a real production-based engine. They entered this engine in 1994, and, as expected, dominated the race. After the race, the rules were changed in order to reduce the amount of boost pressure allowed to be supplied by the turbocharger. The inability of the engine to produce competitive power output after this change caused it to become obsolete after just the one race, as Mercedes-Benz knew it would when deciding a victory at Indy was worth it.

Digifant Engine Management system

The Digifant Engine Management system is an electronic fuel injection system designed by Volkswagen A.G. in cooperation with Robert Bosch GmbH.

Digifant is the outgrowth of the Digi-jet Fuel Injection system first used on early Vanagon vehicles.



History

Digifant was introduced in 1986 on the 2.1L Vanagon Engine. This system combined digital fuel control as used in the earlier Digi-Jet systems with a new digital ignition system. Digifant as used in Golf and Jetta models simplified several functions and added knock sensor control to the ignition system. Other versions of Digifant appeared on the Fox, Corrado, Eurovan as well as later production versions of the rear engined VW Beetle, sold only in Mexico.


Features

Fuel injection control is digital electronic. It is based on the measurement engine load (this signal is provided by the Air Flow Sensor), and on engine speed (Signal provided by the hall sender in the distributor). These primary signals are compared to a map, or table of values, stored in the Engine Control Module (ECM) memory.

The amount of fuel is controlled by the injector (duration). This value is taken from a program in the ECM that has 16 points for load and 16 points for speed. These 256 primary values are then modified by coolant temperature, intake air temperature, oxygen content of the exhaust, battery voltage and throttle position to provide 65,000 possible injector duration points.

Digifant is unlike the earlier CIS and CIS-E fuel injection systems that it replaced in that fuel injectors are mounted on a common fuel rail. The fuel injectors are wired in parallel, and are supplied with Constant System Voltage. The ECM switches the Ground on and off to control duration. All injectors operate at the same time each crankshaft revolution; two complete revolutions being needed for each cylinder to receive the correct amount of fuel for each combustion cycle.

Ignition control is also digital electronic. The sensors that supply the engine load and engine speed signals for injector duration provide information about the basic ignition timing point. The signal sent to the Hall control unit is derived from a program in the ECM that is similar to the injector duration program.

There are 16 points available for load and 16 points for speed. The resulting 256 single operational points are modified by coolant temperature signals and cylinder selective knock control to achieve the optimal ignition point.

Knock control is used to allow the ignition timing to continually approach the point of detonation. This is the point where the engine will produce the most power, as well as the highest efficiency.

Additional functions of the ECM include operation of the fuel pump by closing the Ground for the fuel pump relay, and control of idle speed by a throttle plate bypass valve. The idle air control vale (previously known as an idle air stabilizer valve), receives a changing milliamp signal that varies the strength of an electro-magnet pulling open the bypass valve.

Idle speed stabilization is enhanced by a process known as Idle Speed Control (ISC). This function (previously known as Digital Idle Stabilization), allows the ECM to modify ignition timing at idle to further improve idle quality.



Inputs/Outputs - Digifant II

The 25 pin electronic control unit used in the Golf and Jetta receives inputs from the following sources:

- Hall Sending Unit (Provides Engine Speed Signal) - Air Flow Sensor (Provides Engine Load Information) - Coolant Temperature Sensor - Intake Air Temperature Sensor - Knock Sensor

Additional signals used as inputs are:

- Air Conditioner (compressor on) - Battery Voltage - Starter Signal

The anti-lock brake system, 3-speed automatic transmission and vehicle speed sensor are not linked to this system.

Outputs controlling engine operation include signals to the following:

- Fuel Injectors - Idle air control valve - Hall Control Unit - Fuel Pump Relay - Oxygen Sensor Heater



Additional Systems

The evaporative emission system is controlled by a vacuum operated mechanical carbon canister control valve.

Fuel pressure is maintained by a vacuum operated mechanical fuel pressure regulator on the fuel injector rail assembly.

Inputs and outputs are shown in the following illustration. Digifant II as used on Golf and Jetta vehicles provides the basis for this chart.



System Variants (North America Only)

In North America, Volkswagen released two versions of the Digifant Fuel Injection system. Note that this refers to A2 Golf and Jetta models only.

Digifant I was used exclusively in California market vehicles. Primary differences between Digifant I and Digifant II are as follows:

A limited number of 1987-1990 California Golf and Jetta models are equipped with an On Board Diagnostics system (OBD). These vehicles have blink code capacity to store up to 5 Diagnostic Trouble Codes (DTCs). For the most part, diagnostic troubleshooting is done with a Volkswagen special tool, known as the VAG 1598 and a Digital Multimeter. This system can also have carbon monoxide (CO), ignition timing and idle speed adjusted to baseline values.

In 1991, California Golf, Jetta, Fox, Cabriolet and Corrado vehicles were equipped with expanded OBD capabilities. These later Digifant versions have 38-pin ECMs with Rapid Data Transfer and permanent DTC memory. All Eurovans with Digifant also have rapid data transfer and permanent DTC memory. These systems use a throttle plate potentiometer to track throttle plate position in place of the idle and full throttle switches used on earlier systems.

Another characteristic of Digifant 1 equipped vehicles is a switch mount on the dashboard which has a "Check Engine" symbol.


Summary

Digifant is an engine management system designed originally to take advantage of the first generation of newly developed digital signal processing circuits. Production changes and updates were made to keep the system current with the changing California and federal emissions requirements. Updates were also made to allow integration of other vehicle systems into the scope of engine operation.

Changes in circuit technology, design and processing speed along with evolving emissions standards, resulted in the development of new engine management systems. These new system incorporated adaptive learning, enhanced and expanded diagnostics, and the ability to meet total vehicle emissions standards.



Maintenance of older Digifant Vehicles

In Volkswagen circles, Digifant has often been criticized for it's lack of performance tuning and occasional driveability issues. Most of these issues can be traced back to one of two issues:

- Bad ECM grounds - Faulty Engine Coolant Temperature Sensor (ECT)

The engine coolant temp sensor is located in the coolant flange on the front of the cylinder head.

In the following picture the Digifant Coolant Temperature sensor is clearly visible, as it is identified by a blue electrical connector.


Common issues that are indicative of a failed ECT are:

- Vehicle idles poorly - Engine sputters, might stall - Higher than normal fuel consumption

The part number for this sensor is 025-906-041-A (Always check with your dealer for the most updated part number).

When replacing this sensor, it is important to also replace the clip that holds it in position (032-121-142) and the O-Ring (N-903-168-02).

Once the new sensor has been installed, start the engine and disconnect the blue coolant temperature sensor. Rev the engine through 3000 RPM 3 times, each time allowing the throttle to close completely. This clears the Digifant ECM fault memory.

The 4A-FE DOHC engine

The 4A-FE DOHC engine is very simple, reliable, durable and economical. This engine will never give you a problem if you maintain it well.
1.8L 16 valve model 1ZZ-FE . It has lightweight aluminium block and aluminium head.
Tuned intake manifold allows the engine to perform more evenly.
No more timing belt - using the chain instead allows to reduce maintenance cost. Models after 2001 come with variable timing for better efficiency.
This engine also appears to be very reliable. It has impressive power (120 h.p) and really low fuel consumption. The engine runs very smooth at any speed range, I'd only mention that it's a little more noisy than previous model.

Checking the automatic transmission fluid

Place your car at a level surface and engage the parking brake. Start the engine. Set transmission shifter in "P" (Park) position, and let the engine idle (on some cars this procedure may be different, check the owners' manual for details). Pull the transmission dipstick. Check your owners manual to find where transmission dipstick is located in your car.

Wipe it off with a clean lint free rag. Then insert it back carefully all the way down into its place.

Pull again and check the fluid level. If the engine is cold, it should be within "COLD" marks. If the car was driven and is fully warmed up, the level should be at the upper end of the "HOT" mark. If it's just a little bit lower I wouldn't worry about it. Otherwise I'd top it up. Check the fluid condition also: If it's too black and dirty with burnt smell - your transmission is not going to last. Normally it should be clean and transparent, as in the image. The new fluid comes red. Over the time it becomes brownish. If it is brown, check your owner's manual, may be it's time to change it. Some manufacturers require to change the transmission fluid at 30,000 or 50,000 miles others specify that you never have to change it - check what's your car owner's manual says.

How to top up the transmission fluid:
It's very important to use only specified transmission fluid - check your owners manual or simply visit your local dealer, they alway have proper transmission fluid in stock. Incorrect transmission fluid can even destroy the transmission. Add a small amount of the fluid through the dipstick pipe as shown in the image. Wait for a few minutes - let the fluid to flow down. Recheck the level again. Do not overfill, it also may cause problems with your transmission.

2007 Acura MDX

The Acura MDX is all-new for 2007. It's larger now, and sized right for the job. It's aggressively sporty-looking, it's powerful and its suspension was developed on the Nurburgring, so the sportiness is really there. The interior design is especially zoomy, but not at the expense of function and ease of use.









Body style
5-door SUV

Engine
3.7L (3664 cc) 24 valve SOHC V6 VTEC
300 bhp @ 6000 rpm
275 lb.ft @ 5000 rpm

Wheelbase
108.3 in

Length
190.7 in

Width
78.7 in

Height
68.1 in

Curb weight
4541-4551 lb

Designer Frank Paluch (engineering), Ricky Hsu (styling)

Twincharger

A twincharger is the denomination by the Volkswagen Group of a combination of a turbocharger and a supercharger in an engine. The 1.4 L TSI engine used in some current automobiles like the Volkswagen Golf, Touran employs both methods of forced induction, with the supercharger boosting low-end power while the turbocharger takes over at the high end. VW family of TSI engines also employs Fuel Stratified Injection.

The concept of a twincharger was pioneered by Lancia in the 1980s on the Delta S4 rally car and picked up by Nissan in the March compact car. In addition multiple aftermarket companies have made twincharger kits for cars like the Subaru Impreza WRX, Mini Cooper Type S, Skyline GT-R, Toyota MR-2, etc.

The most common type of twincharging system is a Roots type supercharger paired up with a medium-large sized turbocharger. The supercharger will give better power at low RPM while the turbocharger will give better power at medium-high RPMs. The main drawback of this configuration is that at high speeds, the supercharger (as it is driven by belts) will increase drag upon the engine, limiting the top end power. The Volkswagen Twincharging System overcomes this by locating the supercharger's pulley on a clutch system, which is automatically engaged and disengaged by the computer. This allows the car to keep its top-end performance and automatically switch to supercharging at low RPM.


Drawbacks

There are a few drawbacks to this setup, such as the supercharger still creates drag in the airflow system, even when the clutch is off and the turbocharger is on. It can also cause excessive pulley/belt wear as the clutch engages/disengages at usually very high engine speeds. The transition from the supercharger engaging/disengaging can also be quite rough as well. Lastly, as turbos continue to flow more air as engine speed rises, the turbocharger will eventually outflow more air than it is receiving from the supercharger unless complex piping is used to bypass which can be quite costly and inefficient in a small engine bay.


Solution

The solution to these problems is quite simple, switch the places of both force induction units. By having a turbocharger feed air into a supercharger you gain several benefits as well as minimize any drawbacks from a conventional twincharger setup. The benefits are quite obvious, the supercharger will generate a set amount of boost (determined by pulley size) almost instantly, thus causing the engine to create more exhaust flow and spin the larger turbo quicker. As engine speeds start reaching past the superchargers efficiency under normal circumstances, the turbocharger is providing increasing amounts of air to the supercharger where it would normally run out. All pressure the supercharger receives from the turbocharger is further compressed by whatever the supercharger pulley is rated for. This helps reduce drag on the engine and top speed restrictions isn't as limited.

Simply put, the twincharger concept is a cheaper alternative to the high cost of Nitrous used in many race cars as it provides the instant power without excessive re-filling cost. The twincharger concept itself has not been used on many production cars simply due to the complexity and cost of implementing this system on a vehicle. Another reason simply put is the concept itself is really only viable on sports cars with relatively small displacement engines with high revving capabilities. The main purpose of twincharging is to provide a broad power band, in which the vehicle would perform in just about any RPM speed. This concept is relatively pointless on V8 engines or any vehicles with high torque in stock form as they already possess broad power bands.


Twincharger Vs. Anti-Lag System

Twincharging's biggest benefit over Anti-Lag Systems now being employed in quite a few race cars is the amount of power and reliability it provides. Anti-Lag Systems depend on excessive engine misfiring to keep the turbochargers spooled and thus to maintain the vehicles optimal powerband. Excessive misfiring will cause excessive heat and damage to the turbo manifolds, turbochargers as well as damaging the engine. Anti-Lag Systems make passing Emissions testing next to impossible due to the excessive heat damaging the catalytic converters as well, the Twincharger system does not rely on misfiring at all thus increasing longevity. There are several things such as fuel economy, etc. that are severely compromised.


Other solution

The simplified blow-through system as defined above where the turbocharger feeds the supercharger is inherently flawed as of course the overall airflow is still defined by the rated flow of the supercharger itself, negating any benefits of using the supercharger as the means of purely boosting low engine speed air flow, as it restricts the top end air flow to the same magnitude. A purely supercharged engine would be more efficient. There will be some increases in the SC flow as the air fed to it by the TC becomes more pressurised, but the returns are diminishing and efficiency is reduced.

All systems utilising the twincharging method have a bypass valve that is electronically controlled. At a certain boost and engine speed, the supercharger is bypassed allowing all air to flow past it rather than through it, dedicating the high-flow, high-boost top end power duties to airflow through the turbocharger. The twincharge (or compound charge) systems of today rely heavily on an empirical method where load sites, speeds and airflow characteristics are mapped onto the ecu, which then controls a) the SC bypass valve, and b) the SC clutch. This method can be understood to be not unlike normal engine mapping where fuel and ignition timing are mapped to similar parameters, stored in lookup tables on the ecu, then read and outputted according to what the engine sensors are reading.

As a purely mechanical system, both blow through and suck through systems have their drawbacks when designing a suitable method of transition between the two modes. Historically, compound charged systems relied on the SC blowing into the TC, then when the TC was sucking on the SC hard enough to create a vacuum before the TC intake, a spring loaded valve placed before the TC would open allowing the extra air flow that the turbocharger reqested to be drawn around the SC instead of through it, whilst still using up the boost that the SC was providing. Similarly, the suck through method has a spring loaded valve placed after the turbo charger and before the supercharger, which would open and allow the TC to blow any extra pressurised air around the SC when the SC presented a restriction. These methods of system design are mechanicaly simple, but do not lend themselves to stop start driving where a no-boost moment can be experienced at partial throttle, when the useful boost in the intake escapes back past the partially open valve. It is however suited to cars that spend more time fully accelerating, as during a full bore gearchange the boost would be allowed to vent anyway.

Cummins B Series engine

The Cummins B Series is a family of straight-4 and straight-6 diesel truck and industrial piston engines. The B Series is known for displacing "one liter per cylinder" because of the popular 3.9 L straight-4 and 5.9 L straight-6. A 3.3 L straight-4 is also available. The B Series is widely used in many segments, including pickup trucks (the Dodge Ram), buses, military vehicles, and construction equipment.

The engine was originally designed by Cummins and Case Corporation for commercial truck applications, and appeared in a passenger vehicle, the Dodge Ram, in 1989. It uses a gear-drive camshaft for extra reliability. Also specified is a deep-skirt engine block and extremely strong connecting rods. A Holset turbocharger is used.

The original B Series was updated with 24 valves and an electronic engine management system to become the ISB in 1998.



B5.9

The 5.9 L B5.9 was the first member of the family to be used in a passenger vehicle. Appearing in the 1989 Dodge Ram pickup truck, it quickly became a popular alternative to the large V8 gasoline engines normally used in full-size pickup trucks.

This engine is also used in the Dennis Dart midibus since 1989 as well as usage in light to medium sized commercial trucks and buses.


ISB

The 5.9 L ISB is one of the largest straight-6 engine ever produced for passenger vehicles, and the improved high output 600 version was on the Ward's 10 Best Engines list for 2004.

One unusual feature of the ISB is that it is a multi-valve pushrod engine design. The engine displaces 5883 cc with a 102.1 mm bore and 119.9 mm stroke. A turbocharger output in the high-compression (17.2:1 in recent versions) Diesel. It is an all-iron engine with forged steel connecting rods, an assembled camshaft, and a cast aluminum intake manifold. The engine is produced in Columbus, Indiana.

There have been several versions of the 5.9 L ISB featured in the Dodge Ram. The ISB was first introduced to Dodge Rams in 1989. The Cummins engine in 1991 got an intercooler. In 1994, the engine changed over to a Bosch model P7100 inline-style injection pump from the previous Bosch VE series rotary pump. Midway through model year 1998, The engine was redesigned as a 24 valve model to meet updated emissions requirements and introduced the Bosch VP44 rotary injection pump (featuring electronic control) to the Dodge application. It produced 235 hp (175 kW) at 2700 rpm and 460 ft·lbf (625 Nm) from 1600 rpm to 2700 rpm when paired with a manual transmission, but was slightly downrated when used with automatics.

In 2001, an optional high output (HO) version of the ISB was introduced, producing 245 hp (183 kW) at 2700 rpm and 505 ft·lbf (686 Nm) from 1600 rpm to 2700 rpm when paired with a heavy duty six-speed transmission. The ISB from previous years remained available, and automatic-equipped engines were now rated the same as manuals.

For the 2003 model year, the Cummins was introduced with Bosch high pressure common rail fuel injection, and again, more power. Midway through the 2004 model year, the Cummins 600 was introduced, producing 325 hp (242 kW) at 2900 rpm and 600 ft·lbf (813 Nm)at 1600 rpm. This high torque output gives the engine its name, and also offers a high specific output of 102 ft·lbf (138 Nm) per liter of displacement.

A 610 version, new for the 2005 model year, pushes torque to 610 ft·lbf (827 Nm).


3.9L/4B

The 3.9L/4B Cummins is an excellent high-torque, low-rpm engine in the same family as the 5.9L Cummins turbodiesels. The 3.9L/4B is an inline four-cylinder turbodiesel that was popular for many step van applications including bread vans and other commercial vehicles. This engine is also used in various industrial and construction applications. With a cylinder bore of 4.02 inches and a piston stroke of 4.72 inches, the engine had a wet weight of 745 pounds. In recent years it produced 130hp and 355 lb-ft of torque.


B4.5

The B4.5S is a straight-4 version of the B Series used in agricultural environments. It produces 80–127 hp (60–95 kW). The B4.5 is structurally similar to the six-cylinder B6.7 with both sharing a 104 mm (4.1 in) bore and 132 mm (5.2 in) stroke.


B6.7

The B6.7S is the latest version of the B Series. It is currently the largest straight-6 engine produced for a passenger vehicle. It produces 350 hp (261 kW) and 650 ft·lbf (881 N·m) in the 2007.5 Dodge 2500/3500 pickup trucks and 305 hp (227 kW) and 610 ft·lbf (827 N·m) in the 2007 3500 Chassis Cab. The B6.7 is structurally similar to the four-cylinder B4.5 with both sharing a 104 mm (4.1 in) bore and 132 mm (5.2 in) stroke.

There are many changes over the previous B5.9 for the Dodge truck, the most obvious being the larger displacement. The new engine also includes a cooled EGR system, variable geometry turbocharger, and a new higher-pressure version of the Bosch direct-injection fuel system.

The Dodge trucks' B6.7 competes head to head with V8 engines offered by General Motors and Ford Motor Company, the Duramax and 6.4 L Power Stroke, respectively. All three engines have nearly identical power and torque output specifications and will be released within six months of each other.

Both the B4.5 and B6.7 are used in DAF Trucks' LF45, and LF55 and CF65 range respectively.

Multi-valve

In automotive engineering, an engine is referred to as multi-valve (or multivalve) when each cylinder has more than two valves.

All poppet valve, four-stroke internal combustion engines have at least two valves per cylinder — one for intake of air and fuel, and another for exhaust of combustion products. Adding more valves improves the flow of intake and exhaust gases, potentially improving combustion efficiency, power, and performance. It is not practical to simply use two larger valves because of the circular shape of the combustion chamber and the need for valves to also be round, which ensures they can only cover a fraction of the top of each cylinder; three (or more) smaller valves can replace the largest two valves which could be fitted into the space and result in having a greater effective valve area. Adding more valves per cylinder can improve breathing and thus allow an engine to run at a higher RPM, creating more power for a given displacement, though at a greater complexity and cost.

Most multivalve engines use an overhead camshaft to actuate the valves, and many use double overhead camshafts (DOHC). However this is not always the case: Chevrolet recently showed a 3-valve version of its Generation IV V8 which uses pushrods to actuate forked rockers, and Cummins makes a 4-valve pushrod straight-6 Diesel, the Cummins 600.

Starting in 1922, many of Bugattis engines began using 3 valves per cylinder actuated by a single-ovehead-cam (SOHC). Nissan has produced the 1988-96 KA24E engine with 3 valves per cylinder (two intakes, one exhaust) that are also actuated by (SOHC). Mercedes and Ford are currently producing V6 and V8 engines using this configuration. Ford claims an 80% improvement in high RPM breathing without the added cost of a second cam per bank of cylinders. The Ford design uses one spark plug per cylinder located in the center, but the Mercedes design uses two spark plugs per cylinder located on opposite sides, leaving the center free to add a direct-to-cylinder fuel injector at a later date. Thus there are many considerations to deciding how many valves an engine should have besides just the added cost verses adding breathing capability.

Some versions of the Honda D-series 4 cylinder engines and all J-series V6 and R-series 4 cylinder engines actuate 4 valves per cylinder with a single overhead cam.

Volkswagen, Audi, Ferrari and Yamaha have introduced engines in the past that had a double overhead cam operating 5 valves per cylinder (three intakes, two exhaust). Toyota's 1991-98 4A-GE 1.6-liter 4-cylinder engine also uses 5-valves-per-cylinder and was co-designed by Yamaha as well.

Maserati has produced a 2.0L turbo-V6 engine with 6 valves-per-cylinder (three intakes, three exhaust) (http://www.maserati-alfieri.co.uk/alfieri26.htm).

Engines with two or four valves per cylinder are by far the most common configurations. Four valve per cylinder engines are typically actuated by DOHC, and are too numerous to list.

NOx Adsorbers

The NOx Adsorber or NOx Trap is a device that is use to reduce NOx (NO and NO2) emissions from a lean burn internal combustion engine.


Purpose and Function of a NOx Adsorber

A NOx Adsorber is designed to reduce oxides of nitrogen emitted in the exhaust gas of a lean burn internal combustion engine. Lean burn (diesel) engines present a special challenge to emission control system designers because of the relatively high levels of O2 (atmospheric Oxygen) in the exhaust gas stream. The 3-Way Catalytic Converter technology that has been successfully used on Rich Burn Internal Combustion Engines (typically fueled by petrol but also sometimes fueled by LPG, CNG, or Ethanol) since the middle 1980s will not function at O2 levels in excess of 1.0%, and does not function well at levels above 0.5%. Because of the increasing need to limit NOx emissions from Diesel engines technologies such as Exhaust gas recirculation (EGR) and Selective catalytic reduction (SCR) have been used, however EGR is limited in its effectiveness and SCR requires a reductant, and if the reductant tank is emptied the SCR system ceases to function.

The NOx Adsorber was designed to avoid the problems that EGR and SCR experienced as NOx reduction technologies. The theory is that the zeolite will trap the NO and NO2 molecules - in effect acting as a molecular sponge. Once the trap is full (like a sponge full of water) no more NOx can be adsorbed, and it is passed out of the exhaust system. Various schemes have been designed to "purge" or "regenerate" the adsorber. Injection of diesel fuel (or other reactant) before the adsorber can purge it - the NO2 in particular is unstable and will join with Hydrocarbons to produce H2O and N2. Use of Hydrogen has also been tried, with the same results, however Hydrogen is difficult to store. Some experimental engines have mounted Hydrogen reformers for on board Hydrogen generation, however Fuel Reformers are not mature technology.

NOx Adsorbers are experimental technology as of early 2006, and thus extremely expensive. Whether or not this technology will be successfully commercialized is open to question - only time will tell.


Technical Details

The NOx Adsorber is based on a catalytic converter support that has been coated with a special washcoat containing zeolites.

Dry sump

A dry sump is a lubricating oil management method for four-stroke and large two-stroke piston internal combustion engines that uses a secondary external reservoir for oil, as compared to a conventional wet sump system.

Four-stroke engines are lubricated by oil which is pumped into various bearings and thereafter allowed to drain to the base of the engine. In most production cars, which use a wet sump system, this oil is simply collected in a three to seven litre capacity pan at the base of the engine, known as the oil pan where it is pumped back up to the bearings by the oil pump, internal to the engine. In a dry sump, the oil still falls to the base of the engine, but rather than being collected into an oil pan, it is pumped into another reservoir by one or more scavenger pumps, run by belts from the front or back of the crankshaft. Oil is then pumped from this reservoir to the bearings of the engine by the pressure pump. Typical dry sump systems have the pressure pump and scavenger pumps "stacked up", so that one pulley at the front of the system can run as many pumps as desired, just by adding another to the back of the stack.

A dry sump affords many advantages, namely increased oil capacity, decreased parasitic loss and a lower center of gravity for the engine. Because the reservoir is external, the oil pan can be much smaller in a dry sump system, allowing the engine to be placed lower in the vehicle; in addition, the external reservoir can be as large as desired, whereas a larger oil pan raises the engine even further. Increased oil capacity by using a larger external reservoir leads to cooler oil. Furthermore, dry sump designs are not susceptible to the oil starvation problems wet sump systems suffer from if the oil sloshes in the oil pan, temporarily uncovering the oil pump pickup tube. Having the pumps external to the engine allows them to be maintained or replaced more easily, as well.

Dry sumps are common on larger diesel engines such as those used for ship propulsion. Many race cars, supercars, and aerobatic aircraft also utilize dry-sump equipped engines because they prevent oil-starvation at high g loads and because their lower center of gravity positively affects performance.

Ioe engine

The intake over exhaust (IOE) engine, also known as F-head and pocket valve, is a Four-stroke internal combustion engine of primitive design used in early Harley-Davidson motorcycles. The design was also used in other motorcycles, and in car engines by various manufacturers.

The intake valves are "overhead" (located in the cylinder head) and operated by rocker arms and pushrods from the camshaft in the crankcase, while the exhaust valves are flathead (located in the cylinder or engine block) and operated by the camshaft without pushrods or rocker arms. This was a low compression design.

The ioe design allowed the use of much larger valves than a side valve or overhead valve engine, and was still being used in four wheel drive vehicles in the 1960s. (eg CJ-3B Jeep 1953-1964, 1966 Land Rover Six.)

Crower six stroke

The Crower six-stroke engine is a concept under development by Bruce Crower, known for the invention and manufacture of many devices now used in automotive acceleration racing (see National Hot Rod Association and drag racing).

Two extra strokes are added to the customary internal combustion engine four stroke Otto cycle. A fifth down-stroke is a "steam stroke" and the sixth is to exhaust the expanded steam while venting heat from the engine.

The engine cold starts on the Otto cycle, coasting through the fifth and sixth strokes for a short period. After the combustion chamber temperature reaches approximately 400 degrees Fahrenheit ( 200oC ), a mechanical operation phases in the fifth and sixth cycles. Just prior to the fifth-cycle, water is injected directly into the heated combustion chamber via the converted diesel engines fuel injector pump, creating steam and another power stroke. The phase change from liquid to steam removes the excess heat of the combustion stroke forcing the piston down (a second power stroke). As a substantial portion of engine heat now leaves the cylinder in the form of steam, no cooling system radiator is required. Energy that is dissipated in conventional arrangements by the radiation cooling system has been converted into additional power strokes.


Positive aspects:

Crower claims a 40% reduction in fuel consumption and reduced exhaust emissions.

The base engine for modification uses a high compression ratio which is essential for compression ignition. This high ratio is useful in extracting the full potential of ethanol (one of many fuels that this engine may use). These high ratios are a dramatic alteration over present multi-fuel engines which typically use a 10:1 compression ratio, similar to gasoline engines.

The cooler piston top and reduced combustion chamber temperature (heat is extracted in the conversion of injected water to steam) may allow gasoline to be used at very high compression ratios or without environmentally harmful anti-knock chemicals, which are now in universal use with conventional automobile gasoline engine applications. Under these circumstances, far more energy from the gasoline fuel could be converted to horsepower output. (Very high compression ratios are used in racing engines as a means to increase power.)

The weight of most conventional cooling system parts can be eliminated.

The power loss to operate fans and pumps is eliminated.

The mechanical modifications needed to "six-stroke" a small air-cooled industrial diesel already being manufactured are far less complicated than any hybrid system. Many maintenance features of this engine would be parallel or identical to the knowledge base of mechanics well-versed with gasoline, diesel, and racing engines.

The modification to water injection could be done simultaneous to the use of all liquid and gaseous fuels now in widespread use (diesel, gasoline, ethanol, methanol, LP gas, natural gas as well as all plant-derived oils) in the conventional four-stroke portion of the engine.

Physical engine size reduction is possible as one-third of the engine strokes produce power (in the Crower six-stroke), instead of one-quarter (in the Otto cycle).

The higher percentage of power strokes may allow lower operational speeds, with higher torque output at lower and broader rpm ranges. Lower operational speed might allow designs with greater crankshaft diameter, for the use of engine dimensions with inherently more torque potential.

This system is ideal for heavy industrial applications and electric utility peaking plants where "dirty" internal combustion plants are commonly used for stand-by generation.

This is the only "steam engine" that does not require a certified pressure boiler and related hardware complexities, dangers, and weight penalties.


Obstacles or problems:

A warm up period of at least several minutes would be required in all automotive applications. Power is reduced during the warm-up period.

A steam-free cool down period is required to clear water/steam from the engine.

Cold climate anti-freezing electrical resistance heating systems would be required in the mobile water supply.

Water is more dense than all motor fuels.

Oil adulteration, from the water/steam cycle, is an obstacle to be dealt with, though additional piston/cylinder sealing rings can be added easily.

The weight of an oil separator and a water condenser are likely additions.

Current anti-air pollution legislation does not allow for experimental use status on public roadways.

Engine knocking

Knocking (also called pinking or pinging)— colloquially detonation—in internal combustion engines occurs when air/fuel mixture in the cylinder has been ignited by the spark plug and the smooth burning is interrupted by the unburned mixture in the combustion chamber exploding before the flame front can reach it. The engineered combusting process ceases, because of the explosion, before the optimum moment for the four-stroke cycle. The resulting shockwave reverberates in the combustion chamber, creating a characteristic metallic "pinging" sound, and pressures increase catastrophically.



Normal combustion

Under ideal conditions the common piston internal combustion engine burns its fuel air mix in the cylinder in an orderly and controlled fashion. The combustion is started by the spark plug some 15–40 crankshaft degrees prior to TDC (top dead center) the point of maximum compression. This ignition advance allows time for the combustion process to develop peak pressure at the ideal time for maximum recovery of work from the expanding gases. This point is typically 14–18 crankshaft degrees ATDC (after top dead center).

The spark plug produces an electrical spark that jumps a small gap from its center electrode to its ground electrode. This spark, if the air/fuel mix is within the flammable range for the fuel, initiates combustion. The initial phase forms a small kernel of flame approximately the size of the spark plug gap. For the first few milliseconds of the combustion process, this flame kernel is struggling to survive, producing only slightly more heat than is necessary to continue the combustion process. As it grows in size its heat output increases allowing it to grow even faster.

After this early slow burn phase passes, the flame kernel grows much faster expanding rapidly across the combustion chamber. This growth is due to the travel of the flame front through the combustible fuel air mix itself and due to turbulence rapidly stretching the burning zone into a complex of fingers of burning fuel air that have a much greater surface area than a simple spherical ball of flame would have. This greatly accelerates the combustion process.

In normal combustion, this flame front moves throughout the fuel air mix at a rate characteristic for the fuel-air mixture. Pressure rises smoothly to a peak, burning nearly all the available fuel then falls as the piston decends. In normal combustion this produces a rapid increase in cylinder pressure as the piston passes TDC and begins to move down the cylinder. As mentioned above in a properly tuned engine the maximum cylinder pressure is achieved a few crankshaft degrees after the piston passes TDC, so that the increasing pressure can give the piston a hard push when its speed and mechanical advantage on the crank shaft gives the best recovery of force from the expanding gases.


Detonation

The fuel/air mixture is normally ignited slightly before the point of maximum compression to allow a small time for the flame-front of the burning fuel to expand throughout the mixture so that maximum pressure occurs at the optimum point. The flame-front moves at roughly 33.5 m/second (110 feet/second) during normal combustion[citation needed]. It is only when the remaining unburned mixture is heated and pressurized by the advancing flame front for a certain length of time that the detonation occurs. It is caused by an instantaneous ignition of the remaining fuel/air mixture in the form of an explosion. The cylinder pressure rises dramatically beyond its design limits and if allowed to persist detonation will damage or destroy engine parts.

Detonation can be prevented by:

* The use of a fuel with higher octane rating

* The addition of octane-increasing "lead", methylcyclopentadienyl manganese tricarbonyl (MMT), isooctane, or other antiknock agents.

* Increasing the amount of fuel injected/inducted (resulting in lower Air to Fuel Ratio)

* Reduction of cylinder pressure by increasing the engine revolutions (lower gear), decreasing the manifold pressure (throttle opening) or reducing the load on the engine, or any combination.

* Reduction of charge (in-cylinder) temperatures (such as through cooling, water injection or compression ratio reduction).

* Retardation of spark plug ignition.

* Improved combustion chamber design that concentrates mixture near the spark plug and generates high turbulence to promote fast even burning.

* Use of a spark plug of colder heat range in cases where the spark plug insulator has become a source of pre-ignition leading to detonation.

Correct ignition timing is essential for optimum engine performance and fuel efficiency. Modern automotive and small-boat engines have sensors that can detect knock and retard (delay) the ignition (spark plug firing) to prevent it, allowing engines to safely use petrol of below-design octane rating, with the consequence of reduced power and efficiency.

A knock sensor consists of a small piezoelectric microphone, on the engine block, connected to the engine's ECU. Spectral analysis is used to detect the trademark frequency produced by detonation at various RPM. When detonation is detected the ignition timing is retarded, reducing the knocking and protecting the engine. See also Automatic Performance Control (APC).


Pre-ignition

Pre-ignition is a different phenomenon from detonation, explained above, and occurs when the air/fuel mixture in the cylinder (or even just entering the cylinder) ignites before the spark plug fires. Pre-ignition is caused by an ignition source other than the spark. Heat or hot spots can buildup in engine intake or cylinder components due to improper design, for example, spark plugs with heat range too hot for the conditions, or due to carbon deposits in the combustion chamber. Spark plugs with a high heat range will run hot enough to burn off deposits that lead to plug fouling in a worn engine, but the electrode of the plug itself can occasionally heat soak, and begin glowing hot enough to become an uncontrolled ignition source on its own. Bits of carbon that build up in a combustion chamber can also heat soak to the point where they also are glowing hot and ignite the air-fuel mixture before the proper time.

Pre-ignition and "dieseling" or "run on" are the same phenomenon, except in the latter case the engine continues to run after the ignition is shut off with a hot spot as an ignition source. Pre-ignition might cause rough running due to the advanced and erratic effective igniton timing and may cause noise if it leads to detonation. It may also cause "rumble" which is fast and premature but not detonating combustion.

This heat buildup can only be prevented by eliminating the overheating (through redesign or cleaning) or the compression effects (by reducing the load on the engine or temperature of intake air). As such, if pre-ignition is allowed to continue for any length of time, power output and fuel economy is reduced and engine damage may result. The engine might be slightly harder to get running at once after pre-ignition.

Pre-ignition may lead to detonation and detonation may lead to pre-ignition or either may exist separately.

Charge air cooler

A charge air cooler (also known as an intercooler) is used to cool engine air after it has passed through a turbo charger, but before it enters the engine. The idea is to return the air to the optimum temperature for the combustion of the engine.

Charge air coolers range in size depending on the engine. The smallest are most often referred to as intercoolers and are attached to auto engines or truck engines. The largest are reserved for use on huge marine diesel engines and can weigh over 2 tonnes (see picture).

Marine diesel engine charge air coolers are manufactured in Europe still, despite the very largest engines mostly being built in the Far East. Vestas aircoil A/S and GEA are the oldest makers still in business.

The first marine diesel engine charge air cooler was built by Vestas aircoil A/S in 1956!







4-stroke diesel engine coolers










Location of cooler on large diesel engine

Cold air intake

A cold air intake is a system used to bring down the temperature of the air going into a car for the purpose of increasing the power of the internal-combustion engine. A secondary goal is to increase the appeal of a car by changing the appearance of a car's engine bay and creating an attractive intake noise. These aftermarket parts come in many different colors and many different sizes, and are an inexpensive way to increase performance.



History

The aftermarket company K&N Engineering first offered air intake systems in the late 1980s. Those intakes consisted of rotationally-molded plastic intake tubes and a conical, cotton gauze air filter. In the late 1990s a proliferation of intake manufacturers such as Injen, AEM, Airaid and Volant entered the fray. In addition, oversea manufacturers imported their designs lending to the popularity of Japan domestic market (JDM) air intakes in sport compact markets. K&N and many of the other intake companies now offer intake systems in metal tube designs, allowing a greater degree of customization (the tubes can be powder-coated or painted to match a vehicle).


Mechanics

All cold air intakes operate on the principle of increasing the amount of oxygen available for combustion with fuel. Because cooler air has more density for a given volume, cold air intakes generally work by introducing cooler air from outside the hot engine bay. However, the term "cold air intake" is often used to describe other methods of increasing oxygen to an engine, which may even increase the temperature of the air coming into an engine.

Some strategies used in designing cold-air intakes are:

* increasing the diameter of the air intake, allowing increased airflow.
* smoothing the interior of the intake to reduce air resistance.
* providing a more direct route to the air intake.
* tuning the length of the intake to provide maximum airflow at certain engine speeds (RPM).
* using a more efficient, less restricting air filter.


Application

Intake systems come in many different styles and can be constructed from plastic, metal, rubber (silicone) or composite materials (fiberglass, carbon fiber or kevlar). Due to the limited time air actually remains inside the intake tubing, the materials often do not impact a kit's ability to deliver cool air.

The most basic cold air intake replaces the stock airbox with a short metal or plastic tube leading to a conical air filter, called a Short ram air intake. The power gained by this method can vary depending on how restrictive the factory airbox is. The placement of the filter is usually directly in the engine compartment. The overall benefits depend on the specific application. Power may be lost at certain engine speeds, and gained at others. Because of the increased airflow and reduced covering, intake noise is usually increased. This effect is usually amplified on applications where a resonator, a part intended to reduce intake noise on some vehicles, is replaced by the intake.

Well designed intakes use heat shields to isolate the air filter from the rest of the engine compartment, providing cooler air from the front or side of the engine bay. Carbon fiber can be used for the piping instead of metal, reducing weight and insulating the air from the engine bay in some cases. Carbon fiber and other advanced composites (such as Kevlar) are expensive, and can be more aesthetic rather than functional.

The most extreme designs, sometimes referred to as Complete Cold Air (CCA) intakes, route air from outside the engine bay, usually from the wheel wells (although an extremely poor choice, as the air pressure is low), front grill (high air pressure), or a hood scoop (moderate air pressure). The intake can be placed such that the forward motion of the car pressurises the air coming in, creating a ram-air intake. These intakes often require additional modifications and can require body modifications or replacement panels, such as a replacement "ram air-style" hood. Complete Cold Air intakes can convert to short ram intakes for winter or wet driving.

When using a cold air intake, there is a potential risk when driving in the rain. This is often referred to as "hydrolock", and according to the automotive portal, MODsearch: "Say it's raining cats and dogs and you're out for a spin in your car. Normally you'd love to rip through puddles without thinking twice, but because your engine is now getting air from inside your bumper you have to be careful. If your engine manages to suck up any amount of water through the intake and into the engine you will probably have little to no horsepower left. In more extreme cases, the water brought into the engine through the intake can actually break connecting rods in the pistons, as water will not compress at all, unlike air. In other words, be careful." So, it is important to take the necessary precautions when using a cold air intake so you do not end up getting water in your engine. This may include installing a water shield in your intake or not driving in the rain at all. It is also notable that less damage will occur from water reaching the engine on a rotary engine car, as opposed to a piston engine car. Some cold air intake manufacturers now include a built in hydro-shield, a piece of plastic that blocks water from entering the air filter.

Air bypass valves are gaining popularity in cold air intake manufacturing. An air bypass valve is an open filtered spacer that is positioned more into the engine bay, between two connected pieces of the cold air intake assembly. This prevents hydro-locking by providing an alternate route for air to come in, thus eliminating the vacuum that causes water to be sucked in from a puddle. It is argued that this reduces power, but in actuality it provides more surface area for air enter the engine when the driver presses the pedal. When driving at moderate speeds, the suction caused by the engine is not enough to activate the air bypass valve.

BMC E-Series engine

The BMC E-Series was a straight-4 and straight-6 overhead camshaft automobile engine. It displaced 1.5 litres or 1.8 litres in 4 cylinder and 2.2 litres and 2.7 litres as a 6 cylinder. Although designed when the parent company was BMC, by the time the engine was launched the company had become British Leyland. The engine was eventually replaced by the R-Series, and the S-series in the mid 1980s.




Automobiles using the E-Series

Examples of cars using a version of the E series engine:

* Austin Maxi
* Austin Allegro
* Leyland Princess 2200 cc models, plus Wolseley 2200, Austin 2200 and Morris 2200 badge-engineered versions.
* Leyland Marina
* British Leyland P76
* Rover SDX
* Morris Nomad
* Austin Kimberly
* Austin Tasman



Engine Types

1.5 litre engines

The 1.5 L (1485 cc) version was first used in the Austin Maxi 1969. Output was 69 bhp (524 kW). Bore was 76.2 mm and stroke was 81.3 mm.

Applications:

* Austin Maxi
* Austin Allegro
* Morris Marina


1.8 litre engines

The engine was enlarged to 1748 cc in 1971 by increasing the stroke to 95.75 mm .

Applications:

* Austin Maxi
* Austin Allegro
* Leyland Marina


2.2 litre engines

The 2227 cc version was created by adding two cylinders to the 1.5 litre engine. Bore and stroke remained at the 76 km and 81 km of the 1500 cc version. It was last made in 1982.

Applications:

* Leyland Princess
* Austin Kimberley
* Wolseley 2200


2.6 litre engines

The 2622 cc version was created by increasing the stroke to the 95.75 km used in the 1750 cc version. The power output was 121 bhp and torque 165 ft·lbf.

Applications:

* Leyland P76 (Australia)
* Morris Marina (Australia)
* Rover SDX (South Africa)

BMW 247 engine

The BMW 247 is an air-cooled flat twin motorcycle engine, also known as the "Airhead Boxer". It was used by BMW in its motorcycles from 1969 to 1995.

The /5 was introduced in 1969. The /6 was introduced in 1974. The /7 was introduced in 1977.

Before 1981 the ignition was points ignition. From 1981 it used electronic ignition, a lighter flywheel and was slower.

A number of different models were on the market:

* S: with the most famous BMW R90S R90S who was as fast as the Porsche Boxer in acceleration.
* CS: The Classic Sport, with a 1000cc engine.
* LS: 650cc sport
* ST: An 800cc road-styled GS.
* RS: Racing Sport
* RT: Road Touring
* GS: Gelände/Strasse or Gelände Sport depending on model - many times the winner of the Paris-Dakar rally.

BMW build other air cooled flat twin engines as the 248/1-type used for the R65. Before that they built side-valved and OHV engines commencing with the R32 of 1923. Perhaps the most famous was the R75, the 2WD sidecar motorcycle used by the Wehrmacht in World War II on the African and Eastern fronts.

After World War II, BMW was in a rebuilding period and did not produce any motorcycles in the Allied sector for 1945-1947 and only 59 for 1948.

Air-fuel ratio meter

A meter monitoring the air-fuel ratio of a combustion engine. Also called air-fuel ratio gauge or simply air-fuel meter or air-fuel gauge. It reads the voltage output of an oxygen sensor, sometimes also called lambda sensor, whether it be from a narrow band or wide band oxygen sensor.

The original narrow band sensors became car factory installed standard in the late 70's and early 80's. In recent years, a newer and much more accurate 'wide band' sensor, though more expensive, has come to availability.

Since there are two types of sensors, there are two types of meters, narrow band and wide band.

Most stand-alone narrow band meters have 10 leds and some have more. Also common, narrow band meters in round housings with the standard mounting 2 1/16" and 2 5/8" diameters, as other types of car 'gauges'. These usually have 10 or 20 leds. Analogue 'needle' style gauges are also available.

As stated above, there are wide band meters that stand alone or are mounted in housings. Nearly all of these show the air-fuel ratio on a numeric display, since the wide band sensors provide a much more accurate reading. And since they use more accurate electronics, these meters are more expensive.



Benefits of air-fuel ratio metering.

* Determining the condition of the oxygen sensor: A malfunctioning oxygen sensor will result in air-fuel ratios which respond more slowly to changing engine conditions. A damaged or defective sensor may lead to increased fuel consumption and increased pollutant emissions as well as decreased power, and throttle response.

* Reducing emissions: Keeping the air-fuel mixture near the stoichometric ratio of 14.7:1 (for gasoline engines) allows the catalytic converter to operate at maximum efficiency.

* Fuel economy: An air-fuel mixture at the stoichometric ratio will result in near optimum fuel mileage, costing less per mile traveled and producing the least amount of CO2 emissions. However, from the factory, cars are designed to operate at the stoichometric ratio (rather than as lean as possible while remaining driveable) in order to maximize the efficiency and life of the catalytic converter. While it may be possible to run smoothly at leaner mixtures than 14.7:1, manufacturers must focus on emissions and especially catalytic converter life (which must now be 100,000 miles on new vehicles) {fact} as a higher priority due to EPA regulations.

* Engine performance: Carefully mapping out air-fuel ratios throughout the range of rpm and manifold pressure will maximize power output in addition to reducing the risk of detonation.

Lean mixtures improve the fuel economy but also cause sharp rises in the amount of nitrogen oxides (NOX). If the mixture becomes too lean, the engine may fail to ignite, causing misfire and a large increase in unburned hydrocarbon (HC) emissions. Lean mixtures burn hotter and may cause rough idle, hard starting and stalling, and can even damage the catalytic converter, or burn valves in the engine. The risk of spark knock/engine knocking (detonation) is also increased when the engine is under load.

Mixtures that are richer than stoichometric are necessary when the engine is under heavy load, especially under wide open throttle. The ideal mixture in this type of operation depends on the individual engine. For example, engines using forms of forced induction such as turbochargers and superchargers typically require a richer mixture under wide open throttle than naturally aspirated engines.

Cold engines also typically require more fuel and a richer mixture when first started, because fuel does not vaporize as well when cold, and because cold air is denser, and therefore requires more fuel to properly "saturate" it. Rich mixtures also burn cooler and decrease the risk of spark knock/engine knocking (detonation) when the engine is under load. However, rich mixtures sharply increase carbon monoxide (CO) emissions.


Oxygen sensor types.

Oxygen sensors are installed in the exhaust system of the vehicle, attached to the engine's exhaust manifold, the sensor calculates the ratio of the air-fuel mixture.

As mentioned above, there are two types of sensors available; narrow band, and wide band. Narrow band sensors were the first to be introduced. The wideband sensor was introduced much later.

A narrow band sensor has a non-linear output, and switches between the thresholds of lean (ca 100-200 mV) and rich (ca 650-800 mV) areas very steeply.

Also, narrow band sensors are temperature-dependent. If the exhaust gases become warmer, the output voltage in the lean area will rise, and in the rich area it will be lowered. Consequently, an oxygen sensor, without pre-heating, has a lower lean-output and a higher rich-output, possibly even exceeding 1 Volt. The influence of temperature to voltage is smaller in the lean mode than in the rich mode. A "cold" engine makes the sensor switch the output voltage between ca 100 and 850/900 mV and after a while the sensor may output a switch voltage between ca 200 and 700/750mV, for turbocharged cars even less.

The ECU tries to maintain a stoichiometric balance, wherein the air-fuel mixture is approximately 14.7 times the mass of air to fuel. This, in order to maintain a neutral engine performance (lower fuel consumption yet decent engine power and minimal pollution.).

The average level of the sensor is defined as 450 mV. Since narrow band sensors cannot output a fixed voltage level between the lean and the rich areas, the ecu tries to control the engine by controlling the mixture between lean and rich in such a sufficiently fast manner, that the average level becomes ca 450 mV. Mixtures that are less than 14.7 to 1 are rich, and more than 14.7 to 1 are lean.

A wideband sensor, on the other hand, has a very linear output, 0 - 5 V, and is not temperature dependent.


Which type of air-fuel ratio meter to be used.

If the purpose of the air-fuel ratio meter is to diagnose an existing or possible problem with the sensor and/or to check the general mixture, and performance, a narrow band air-fuel ratio meter is sufficent.

In high-performance tuning applications, however, the wide-band system is desireable.

Changing Your Car Oil

# Go to the parts house and for most cars buy six quarts (US) of good oil. Here we recommend staying with the manufacturers recommended (check your owners manual) oill for your car. Your engine will need about five of those quarts (also check your owners manual for the correct amount) and you keep one in the trunk in case the car needs an extra quart during the operation of the vehicle. About oil: I don't know what brands are available to you folks in Canada. In the USA some of the best are Pennzoil, Quaker State, Castrol, and Valvoline. If any of these are readily available to you, use them for long engine life. Most brands are very good, though, and don't knock yourself out trying to find these. What is important is: whatever the brand you chose, stay with that brand forever. Do not mix oil! If you chose a synthetic oil such as our Mobil1, do not mix regular oil with synthetic oil.

# Pick up a good oil filter for the vehicle. In the USA, the best filter we now know of is the Fram Dual-Guard. When I say good filter, I mean one that will do the job removing the carbon and such from the engine oil. Talk to your mechanics and find out what is the best in Canada. We also have Purolator and a significant amount of "cheap" filters. Always go with the best. A good filter is a lot cheaper than an engine overhaul.

# Pick up a decent "oil filter wrench" from you local hardware store or parts house. There are several different style of these items and the key phrase is "working in close quarters". Chose one that will do the job for you and get the filter off the engine. I, personally, use a metal strap wrench because I have never found a vehicle that it wouldn't fit or do the job.

# Buy a decent oil container pan to put under the car to receive the oil. Forget the old dishpan or bucket. You need a pan that will contain the oil that can be closed to seal the oil after it is drained. Why? Because you are going to be a good citizen and recycle the oil after it is drained rather than dump it in the trash or on the ground. God gave us this earth to live on and use, but not abuse. Okay, you're ready to start the process. First, understand that if oil gets on your hands or arms, it's not like acid. Mechanics use clean engine oil to wash off dirty oil, but afterwards wash thoroughly with soap and water. Petroleum based products are better off off the skin.

# Elevate the front of the vehicle using the car jack. Elevate it only enough to give you access to the underside of the engine and give you some room to move a wrench. Use "jack stands" when ever possible. Never depend on your car jack while you under the car. Too many fail and too many folks get crushed when the car comes down.

# Locate the oil fill cap on the engine (usually on the valve cover) (usually where you add oil to the engine). Remove it and set it aside.

# Locate the engine pan plug on the lowest part of the engine oil pan. If you read the Haynes Manual, you know that the oil pan is covering the entire bottom end of the engine. The drain plug will have a hexagonal head on it and may be any size from 13mm to 17mm.

# Locate the oil drain pan that you bought (to contain the oil) directly under the drain plug on the engine.

# Using a socket wrench or a combination wrench of the right size, loosen the oil drain plug on the engine and remove it completely. You will get some oil on your hands (but, who cares?).

# Let the oil drain completely from the engine. Go have a cigarette, drink a beer, or whatever. Let it drain completely into the container under the vehicle.

# Replace the drain plug on the engine oil pan. Rule of thumb is that you tighten the drain plug tight. How tight is tight? Well, I use a combination wrench (the closed end) and use one finger to pull it tight. When my one finger cannot pull it any tighter, that is tight enough. If you don't have much strength in your hands, use two fingers to pull the wrench...but no more. That will seal the drain plug and keep you from stripping the threads out of the oil pan.

# Next move the drain pan to a point under the oil filter. Use your filter wrench and rotate the filter counter-clockwise to remove it. Counter-clockwise means you are looking at the filter on the engine from the bottom. A couple of turns with the filter wrench and the oil filter will come free from the engine. At that point, you can unscrew it with your hands and drop it into the pan beneath it. Oil will escape from the filter and drain down into the pan. This is normal.

# Open the new filter in it's box and you will notice that it has a rubber gasket on the base. Open one of the bottles of engine oil and take a "little oil" from it to coat the rubber gasket thoroughly. If you don't do this, you won't get the filter off the engine the next time. The rubber gasket will seal itself to the engine and cause you a lot of grief.

# Screw the new filter onto the filter pipe coming out of the engine and screw it down to the base (using hands only). Turn it with your hands until it is tight. Use the filter wrench you bought and turn the filter one quarter turn more to seal it. Note: Some say turn it 1/2 turn more. Smokey says 1/4 turn is sufficient and will make it a lot easier to loosen next time. Okay, you are done under the car. Release the jack and the whatever else you are using to hold the car in the UP position. Remove your drained oil and its container for proper disposition later. Put the car on the ground in normal driving status.

# Find the engine oil fill on the valve cover and add five quarts (US) of new engine oil. Cap the oil fill hole.

# Pull the engine dipstick and check the oil level. You will find that it reads one (US) quart high. Reason: The filter is empty. This extra quart resides in the filter when the engine is shut down.

# Start the engine but do not rev the engine. Just let it idle. The light on the dash that says "OIL" will illuminate for a brief time and them extinguish. This is the time for your oil pump to pick up the new oil and pressurize the system.

# Let the vehicle engine run for about five minutes. This will warm up the engine and let the oil circulate. It will also give you a chance to make sure the filter is not leaking. Check under the vehicle and make sure you are not leaking oil onto the pavement.

# Shut the engine off. Check the dipstick on the engine and it should read "FULL". You should have no oil leaks under the engine. The next time you have to do all of this is 3000 miles or approximately 5000 Km. If you value your engine and your car, you will maintain this schedule. Every Km you drive over this figure means wear on the engine and early engine failure. ALWAYS CHANGE YOUR FILTER WITH EVERY OIL CHANGE!!!!

source:doityourself.com

How to Clean a Car Battery

What You Need

* Baking Soda and Stiff Brush
* Rubber Gloves
* Wrench to Fit Cable Clamp
* Wrench to Remove Battery
* Waterproof Grease

1. After loosening the cable clamps and battery holder, remove the battery from vehicle.

2. Begin by cleaning the entire battery top of dirt and oxidation using baking soda and water.

3. While battery is out, clean the cable clamps until shiny with the #535 brass brush.

4. Re-install battery in vehicle. Re-attach clamps and cover the connection with grease.

Engine balance

Engine balance is the design, construction and tuning of an engine to run smoothly. Engine balance reduces vibration and other stresses, and may improve the performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress both on other machinery and on the people near the engine.


These benefits are produced by:

* Reduced need for a heavy flywheel or similar devices.
* Reduced wear.
* The opportunity to reduce the size and weight of components (other than the obvious one of the flywheel) as a result of reduced stress and wear.
* Reduced vibration transmitted to the surroundings of the engine.
* The opportunity to extract more power from a given engine by:
o Higher maximum operating speeds made possible by reduced stress.
o Spreading loads equally over multiple components, for example if multiple carburetors are poorly balanced, the maximum available throttle will be reduced.

Even a single cylinder engine can be balanced in many aspects. Multiple cylinder engines offer far more opportunities for balancing, with each cylinder configuration offering its own advantages and disadvantages so far as balance is concerned.


Inherent mechanical balance

The mechanical balance of a piston engine is one of the key considerations in choosing an engine configuration.


Primary and secondary balance

Historically, engine designers have spoken of primary balance and secondary balance. These terms generally refer to the order in which the problems of engine balance were addressed as piston engines developed. Because of this they also to some degree reflect the importance of these aspects of balance, but not absolutely, nor do they cover all aspects of mechanical balance.

The definitions used of primary and secondary balance also vary. In general, primary balance is the balance achieved by compensating for the varying momentum (but not the varying kinetic energy) of the pistons during rotation of the crankshaft. Secondary balance can include compensating (or being unable to compensate) for:

* The kinetic energy of the pistons.
* The non-sinusoidal motion of the pistons (which may otherwise be regarded as part of primary balance).
* The sideways motion of crankshaft and balance shaft weights.
* Various rocking motions produced by displacement of balancing masses and not included as primary balance (such as the unwanted offset of opposing cylinders in the boxer engine necessitated by the crankshaft design).

Despite claims by designers and manufacturers, no configuration is perfectly balanced. However by adopting particular definitions for primary and secondary balance, particular configurations can be correctly claimed to be perfectly balanced in these restricted senses. That is not to say that there is no substance to these claims. In particular, the straight six, the flat six, and the V12 configurations offer exceptional inherent mechanical balance.

Vibrations not normally included in either primary or secondary balance include the uneven firing patterns inherent in some configurations. Many definitions of secondary balance also exclude some aspects of mechanical balance.


Single cylinder engines

A single cylinder engine produces three main vibrations. In describing them we will assume that the cylinder is vertical.

Firstly, in an engine with no balancing counterweights, there would be an enormous vibration produced by the change in momentum of the piston, connecting rod and crankshaft once every revolution. Nearly all single-cylinder crankshafts incorporate balancing weights to reduce this.

While these weights can balance the crankshaft completely, they cannot completely balance the motion of the piston, for two reasons. The first reason is that the balancing weights have horizontal motion as well as vertical motion, so balancing the purely vertical motion of the piston by a crankshaft weight adds a horizontal vibration. The second reason is that, considering now the vertical motion only, the smaller piston end of the connecting rod is closer to the larger crankshaft end of the connecting rod in mid-stroke than it is at the top or bottom of the stroke, because of the connecting-rod's angle. The piston therefore travels faster in the top half of the cylinder than it does in the bottom half, while the motion of the crankshaft weights is sinusoidal. The vertical motion of the piston is therefore not quite the same as that of the balancing weight, so they can't be made to cancel out completely.

Secondly, there is a vibration produced by the change in speed and therefore kinetic energy of the piston. The crankshaft will tend to slow down as the piston speeds up and absorbs energy, and to speed up again as the piston gives up energy in slowing down at the top and bottom of the stroke. This vibration has twice the frequency of the first vibration, and absorbing it is one function of the flywheel.

Thirdly, there is a vibration produced by the fact that the engine is only producing power during the power stroke. In a four-stroke engine this vibration will have half the frequency of the first vibration, as the cylinder fires once every two revolutions. In a two-stroke engine, it will have the same frequency as the first vibration. This vibration is also absorbed by the flywheel.


Two cylinder engines

Even a two cylinder engine has three common configurations:

* Straight-twin.
* V-twin.
* Boxer twin.

Each of the three has advantages and disadvantages so far as balance is concerned.

A straight twin engine may have a simple single-throw crankshaft, with both pistons at top dead centre simultaneously. For a four-stroke engine, this gives the best possible firing sequence, with one cylinder firing per revolution, equally spaced. But it also gives the worst possible mechanical balance, no better than a single cylinder engine. Many straight twin engines therefore have an offset angle crankshaft, that is, two throws at an angle of up to 180°, with the result that the pistons reach top dead centre at different times. This produces better mechanical balance, but at the cost of uneven firing.

The first vibration noted above for the single cylinder is minimised for a crank offset angle of 180°, but balance is still far from perfect. There is still a rocking moment produced by the displacement of the cylinders one from the other, and there is still the second vibration noted for the single cylinder owing to the kinetic energy of motion of the pistons. This second vibration is minimised by a crank offset of 90°. See external links below for a detailed analysis of the effect of different crankshaft offset angles.

A "true" V-twin, like all true V engines, has only one crank throw for each pair of cylinders, so the crankshaft is a simple one like that of a single cylinder engine, and unlike any other V engine no crankshaft offset is possible. However there is still the question of the angle of the V. An angle of 90° gives a very good mechanical balance, but the firing is uneven. Smaller angles give poorer mechanical balance, but more even firing for a four-stroke (but, even less even firing for a two-stroke). Many classic V-twin motorcycles use narrow V angles as a compromise. See external links for a detailed analysis of the 90° V twin mechanical balance.

Other engines with two cylinders in a V configuration have a small offset between the cylinders in order to allow two separate crank pins, set at whatever angle the engine designer may specify in similar fashion to a straight twin. Although the characteristics of such engines are similar to those of a straight twin rather than a V, they are almost always called V engines. These engines include the Suzuki VX800 and Honda Transalp, which although called V-twins have a two-pin crankshaft, and an offset angle between the two crank throws.

The boxer engine is a type of flat engine in which each of a pair of opposing cylinders is on a separate crank throw, offset at 180° to its partner, so both cylinders of the pair reach top dead centre together. Any boxer therefore is inherently balanced so far as the momentum of the pistons is concerned, except that corresponding cylinders cannot exactly line up owing to the crankshaft design, and this produces a rocking motion. The four-stroke boxer twin has an even firing pattern, but the worst possible balance so far as the kinetic energy goes, as both pistons accelerate and deccelerate together. See external links for a detailed analysis of the boxer twin mechanical balance.


More than two cylinders

The number of possible configurations with more than two cylinders is enormous. See articles on individual configurations listed in Category:Piston engine configurations for detailed discussions of particular configurations.

There are four different forces and moments of vibration that can occur in an engine design: free forces of the first order, free forces of the second order, free moments of the first order, and free moments of the second order. The straight-6, flat-6, and V12 designs have none of these forces or moments of vibration, and hence are the naturally smoothest engine designs. (See the Bosch Automotive Handbook, Sixth Edition, pages 459-463 for details.)

Engines with particular balance advantages include:

* Straight-6
* Flat-6
* Flat-12
* V12

Engines with characteristic problems include:

* Flat-4 boxer and straight-4 have no better kinetic energy balance than a single, and require a relatively large flywheel.
* Crossplane V8, which requires a very heavily weighted crankshaft, and has unbalanced firing between the cylinder banks (producing the distinctive and much-loved V8 "burble").
* Flatplane (180° offset crankshaft) V8.

In modern multi-cylinder engines, many inherent balance problems are addressed by use of balance shafts.


Steam engines

The question of mechanical balance was addressed on steam engines long before the invention of the internal combustion engine. Steam locomotives commonly have balancing weights on the driving wheels to control wheel hammer caused by the up and down motion of the tie rods and to some degree the connecting rods. Again, the balance is a compromise, and some main line locomotives such as the Australian 38 class have no such weights.


Component balancing

In order to achieve the inherent balance of any engine configuration, the balancing masses must be matched. In most engines, some individual components are matched as a set. Exactly which components are matched is part of the design of the engine.

For example, pistons are often matched, and must be replaced as a set to preserve the engine balance. Less commonly, a piston may be matched to its connecting rod, the two being machined as an assembly to tighter tolerances than either alone.

Component balancing is not restricted to considerations of mechanical balance. It is vital, for example, that the compression ratio and valve timing of each cylinder should be closely matched, for optimum balance and performance. Many components affect this balance.


Blueprinting

Blueprinting is the remachining of components to tighter tolerances to achieve better balance.

Ideally, blueprinting is performed on components removed from the production line before normal balancing and finishing. If finished components are blueprinted, there is the risk that the further removal of material will weaken the component. However, lightening components is generally an advantage in itself provided balance and adequate strength are both maintained, and more precise machining will in general strengthen a part by removing stress points, so in many cases performance tuners are able to work with finished components.


Carburetor balance

In engines with multiple carburetors, balancing the carburetors is a vital part of engine tuning. Imbalance will not only mean that the carburetors are operating at less than ideal, but will also unbalance the cylinders that they serve.

2007 Ford Shelby GT500

Shelby and Ford returned with a Shelby-branded Mustang, the Shelby GT500 for 2007. Introduced at the 2005 New York International Auto Show, the GT500 uses a 5.4L (that was modified by Australia for their use in their 2006/2007 Ford Falcon Boss 290 BF GT) Modular supercharged V8. 500 hp and 475 ft·lbf (644 N·m) will be available, designed to outperform all previous Mustangs. A Tremec 6-speed manual transmission, suspension tuning, a body kit, and 18 inch wheels complete the car. The name "Mustang" does not appear in the official model name nor does it appear as branding on any part of the vehicle.

A collaboration of Ford's Special Vehicle Team (SVT) and Carroll Shelby, the GT500 will be produced in limited quantity for three years (approximately 10,000 units/year) on the line at Ford's Flat Rock, Michigan (AutoAlliance) assembly facility.

The right to purchase the first 2007 Shelby GT500 was auctioned off at the Barrett-Jackson Collector Car Auction on 21 January 2006 in Scottsdale, Arizona for $648,000. Proceeds will benefit the Carroll Shelby Children's Foundation.


Performance

The heavy iron block V8, with supercharger and water-to-air intercooler, shifts the weight bias further forward than the standard Mustang GT (57/43%; front/rear), but the car is said to handle predictably and ride comfortably. According to Car & Driver, a Corvette Z51 was deemed to be a better performance vehicle based on the tests performed, but the Shelby was found to be more practical, and to offer a more comfortable ride. They stated that the Shelby offered the "best [overall] bang for the buck around."

The January 2007 issue of Road & Track featured a comparison test between the Shelby GT500, Mustang GT/CS, Corvette Z51, and Corvette Z06. The 500 hp GT500 performed 0-60 mph in 4.6 seconds where as the 400 hp Corvette Z51 made it in 4.5 seconds. The 505 hp Z06 completed this in 3.6 seconds. The GT500 performed a quarter-mile test in 12.8 seconds at 113.2 mph where as the Corvette Z51 made it in 12.8 seconds at 112.5 mph (Z06 in 12.0 seconds at 121.0 mph). These results may be due to the GT500 (3950 lb) being 660 lb heavier than the Corvette Z51 (3290 lb). In comparison, the 300 hp Mustang GT/CS had a 0-60 mph time of 5.3 seconds and a quarter-mile time of 13.9 seconds at 103.0 mph.

Series 9, episode 6 of the BBC's Top Gear saw a GT500 go round their track in 1:30, about the same as a VW Golf R32 or Audi S4. They were very critical of Ford's failure to upgrade the suspension and brakes along with the engine, unlike the less powerful Roush Mustang Stage III which managed a lap of 1:28. In comparison the standard Corvette managed 1:26.8, and the Z06, 1:22.4. On a rolling road, they only saw 440hp from the GT500.

Top speed of the GT500 is 150 mph electronically limited compared to the Z51's 186 mph non-limited. Even without the electronic limitation the Shelby is not expected to pass 170 mph according to Ford Engineers whose comments were based on wind tunnel experiments and drag co-efficient numbers (0.38).

Deliveries of the Shelby GT500 began in May 2006.


Powertrain:
5.4-liter, DOHC, 32-valve V8, with Roots-type supercharger (8.5 psi max boost); six-speed manual transmission; rear wheel drive

Horsepower:
500 at 6,000 rpm

Torque:
480 pound-feet at 4,500 rpm

Curb weight:
3,920 pounds

0-60 mph:
4.5 seconds

Wheelbase:
107.1 inches

Overall length:
188 inches

EPA fuel economy:
15 miles per gallon city, 21 mpg highway

2007 Saturn Vue Green Line

TYPE:
Front-drive, 5-door, 5-passenger, compact, hybrid, SUV.

PRICE:
$22,370 base

KEY RIVALS:
Toyota Highlander Hybrid, Ford Escape Hybrid, Honda Accord Hybrid.

POWER:
2.4-liter, DOHC, inline 4-cylinder Ecotec engine producing 162 foot-pounds torque; GM Hybrid System, 14.5 kilowatt electric motor producing 115 foot-pounds peak torque; Hydra-Matic 4T45-E 4-speed automatic transmission.

FUEL ECONOMY:
27 city, 32 highway mpg.

CHASSIS:
Steel spaceframe; independent suspension with anti-roll bars, front struts, three rear lateral locating links and coils springs; power rack-and-pinion steering; traction control; power disc/drum brakes with ABS; 16-inch aluminum alloy wheels.

LENGTH X WIDTH X HEIGHT:
181.3 x 71.6 x 65.3 inches.

WHEELBASE X TRACK:
106.6 x 61.3/61.2 inches.
GROUND CLEARANCE:
6.9 inches.

CURB WEIGHT:
3,474 pounds.

STANDARD:
Front air bags, rear window washer/wiper, theft deterrent system, battery rundown protection, tire inflator kit, air conditioning, power windows/locks/mirrors, remote keyless entry, steering wheel audio controls, AM/FM/CD stereo, foldaway rear cargo organizer, center console.

Atkinson cycle

The Atkinson cycle engine is a type of Internal combustion engine invented by James Atkinson in 1882. The Atkinson cycle is designed to provide efficiency at the expense of power, and is beginning to see applications in modern hybrid electric applications.


Design

The original Atkinson cycle engine allows the intake, compression, power, and exhaust strokes of the four-stroke cycle to occur in a single turn of the crankshaft, and was designed to bypass patents covering the existing Otto cycle engines. Owing to the extra linkage in the Atkinson engine, the expansion ratio may differ from the compression ratio. By adjusting the linkage to allow a power stroke longer than the compression stroke, the engine can achieve greater efficiency than with the Otto cycle engine. While Atkinson's engine design is no more than a historical curiosity, the Atkinson cycle, where the power stroke is longer than the compression stroke, is beginning to become common due to the increase in fuel economy it provides.



Four stroke Atkinson cycle engine

The Atkinson cycle may also refer to a four stroke piston engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold. This reduces the effective compression ratio and, when combined with an increased stroke and/or reduced combustion chamber volume, allows the expansion ratio to exceed the compression ratio while retaining a normal compression pressure. This is desirable for improved fuel economy because the compression ratio in a spark ignition engine is limited by the octane rating of the fuel used. A high expansion ratio delivers a longer power stroke, allowing more expansion of the combustion gases and reducing the amount of heat wasted in the exhaust. This makes for a more efficient engine.

The disadvantage of the four-stroke Atkinson cycle engine versus the more common Otto cycle engine is reduced power density. Because a smaller portion of the intake stroke is devoted to compressing the intake air, an Atkinson cycle engine does not take in as much air as would a similarly-designed and sized Otto cycle engine.

Four stroke engines of this type with this same type of intake valve motion but with forced induction (supercharging) are known as Miller cycle engines.


Rotary Atkinson cycle engine

The Atkinson cycle can be used in a rotary engine. In this configuration an increase in both power and efficiency can be achieved when compared to the Otto cycle. This type of engine retains the one power phase per revolution, together with the different compression and expansion volumes of the original Atkinson cycle. Exhaust gases are expelled from the engine by compressed air scavenge. This modification of the Atkinson cycle allows for the use of alternative fuels like Diesel and hydrogen. See External Links for more information.



Vehicles using Atkinson cycle engines

While a modifed four stroke engine using the Atkinson cycle provides good fuel economy, it is at the expense of a lower power-per-displacement than a traditional four stroke. If the engine is only run at high powers intermittently, then the power of the engine can be supplemented by an electric motor during times when high power is needed. This forms the basis of an Atkinson cycle based hybrid electric drivetrain. These electric motors can be used independently of, or in combination with, the Atkinson cycle engine, to provide the most efficient means of producing the desired power.

Multiple production vehicles use Atkinson cycle engines:

Toyota Prius hybrid electric (front-wheel-drive) with a compression ratio of 13.0:1
Ford Escape/Mercury Mariner/Mazda Tribute hybrid electric (front- and four-wheel drive) with a compression ratio of 12.4:1
Toyota Camry Hybrid hybrid electric (front-wheel drive) with a compression ratio of 12.5:1

Note that any compression ratio shown above only reflects the physical compression ratio, which provides the ratio of the combustion chamber volumes when the piston is at "bottom dead center" versus "top dead center". The effective compression ratio of the air-fuel mixture in an Atkinson cycle engine, with respect to atmospheric pressure, is lower due to the aforementioned delay in closing the intake valve.

GMT900

The GMT900 debuted at the 2006 North American International Auto Show, as the next generation full-size pickups and SUVs, and replacements for the GMT800 vehicles. The first GMT900 vehicle is the next-generation Chevy Tahoe.

GMT900 has been called a "Hail Mary pass" for General Motors — the company needs the revenue from these large trucks to continue operating profitably, and the failure of the series could result in insolvency. The company's resources were focused exclusively on GMT900 development through 2005, delaying other programs like the GM Zeta platform. With the 2005 spike in gasoline prices, some analysts have questioned the wisdom of "betting the company" on a line of large trucks, but initial sales have been brisk with no need to resort to rebates.

The GMT900 series features standard vehicle stability control. Original plans called for American Axle's "I-Ride" independent suspension module in the rear, but this appears to have been cancelled.

Short wheelbase (Yukon/Tahoe) GMT900 production began at GM's Arlington Assembly plant in Arlington, Texas on December 1, 2005, six weeks ahead of schedule. Production of the SWB versions began at Janesville Assembly in Janesville, Wisconsin in early 2006. Production of long wheelbase trucks (Suburban/Yukon XL) begins in Janesville and at Silao Assembly in Silao, Mexico in March. The Avalanche will be produced only in Silao, while the Escalade will be based in Arlington.

The SUVs began to show up at dealers in February 2006. Sales so far have exceeded expectations, with GM asking suppliers to ramp up parts production in advance of the launch of the remaining models.

The related Silverado and Sierra pickups will start production in late 2006. Interestingly, the original Hummer H2 does not appear that it is to be carried over to the GMT900 platform.

Belt alternator starter

General Motors introduced a mild hybrid system called belt alternator starter (or BAS) in the 2006 Saturn VUE Green Line. It operates similar to the "start-stop" system used in the Chevrolet Silverado Hybrid in that it shuts down the engine when the vehicle comes to a stop and instantly restarts it when the accelerator is pressed. A 48 volt electrical system is used to operate all accessory equipment, from the air conditioning to the lighting, making the system essentially invisible to the driver.

The BAS system goes slightly further than the Silverado, however, in providing some modest power assist for "acceleration feel", according to GM. Although not as effective as other systems, the BAS system is expected to provide about 15% fuel efficiency gain for the compact VUE.

One major benefit of the BAS technology is that it fits in the same space as a conventional engine. No modifications were required to the VUE's chassis to accommodate the BAS system, with the battery pack housed in the spare tire well. This allows the VUE Green Line to be produced on the same assembly line as the normal VUE, producing substantial cost savings and allowing the company to adjust production more easily.

The BAS system uses a conventional 4T45-E automatic transmission.

This system will eventually find its way to other GM models, including the Saturn Aura, and Chevrolet Malibu.

Multi-Displacement System

DaimlerChrysler's Multi-Displacement System (MDS) is an automobile engine variable displacement technology. It debuted in 2004 on the 5.7 L modern Hemi V8. Like Mercedes-Benz's Active Cylinder Control, General Motors' Displacement on Demand, and Honda's Variable Cylinder Management, it deactivates four of the V8's cylinders when the throttle is closed.

The system was first offered only on passenger cars, since the heavy demands of trucks would interfere with its operation. However, it was recalibrated for 2006 and will be offered on all seven models, including trucks, using the 5.7 L engine.

Chrysler expects that the technology will boost economy by 10% to 20%. In the Jeep Grand Cherokee with MDS, highway fuel mileage for the V8 is the same as the V6 at 21 mpg (11.2 liters per 100 km).

In order to preserve the characteristic rumble of the V8 engines, Chrysler and Eberspaecher North America designed a special exhaust system for MDS-equipped vehicles. This includes four separate mufflers, two large central ones for V8 mode and two smaller ones near the tailpipes for straight-4 operation. Unlike the system used on Mercedes-Benz V12 engines, also designed by Eberspaecher, the system is mechanically passive.

Applications:

* 2005- Chrysler 300C
* 2005- Dodge Charger
* 2005- Dodge Magnum
* 2005- Jeep Grand Cherokee
* 2006- Dodge Durango
* 2006- Dodge Ram
* 2006- Jeep Commander

Power band

The power band of an engine refers to the range of operating speeds under which the engine is able to operate efficiently. A typical gasoline automotive engine is capable of operating at a speed of between around 750 and 6000 RPM, but the engine's power band would be more limited. The engine would typically not generate maximum torque until higher operating speeds of perhaps 2500 RPM, after such, the torque drops off. The peak power (horsepower) might be closer to 5000 RPM. Such an engine would be said to have a "power band" of 2500-5000 RPM (another example would be from torque peak to redline: 2500-6000 RPM).

A more precise definition of the power band: the rpm range where an engine makes at least 75% of its maximum torque.

This can be applied to any engine and establishes a reliable quantification of the above notion "the engine is able to operate efficiently".



Power Band Tuning Considerations

The tuning of the power band is a great challenge. It is possible to create a peaky engine which generates more power from an engine if the manufacturer is willing to tune it for a very narrow power band. However, an engine with a narrow power band is more difficult to use. Such an engine must be coupled to a close-ratio transmission with many gears in order to remain in its power band while providing an acceptably wide range of output speeds. A flexible engine has a wide power band with less peak power, but could be tied to a less complex transmission with fewer gears and would not need to shift gears as often. Such an engine is also often called torquey because it maintains a more constant level of torque over a wider range of RPM.


Cost and Usage Considerations

Sports cars and other performance vehicles are generally designed for peak power in a narrow power band. In these vehicles, the higher cost of a complex transmission would be more acceptable, and the driver could be assumed to be more willing to shift gears often to remain in the power band. These vehicles attempt to achieve the greatest possible power to weight ratio, and benefit greatly from using a smaller engine tuned for high peak power rather than a large engine with a wide power band. Trucks and full-size cars are more often tuned for a wide power band and use larger engines to achieve acceptable power over a wide range. These vehicles have the benefit of not having to shift as often as vehicles with a narrow power band.


Tuning for high Horsepower Output or high Torque Output?

Since automobile shoppers rely heavily on the peak power output figure (typically given in horsepower or kilowatts), some auto makers tend towards producing "peaky" engines. For example, Honda's 2006 Civic Si generates 197 hp (147 kW) at 7800 RPM. Though it produces a fairly flat torque curve compared to many engines, it only produces 139 ft·lbf (188 N·m) and it has relatively sharp (or "peaky") power delivery, this requires the driver to keep the engine at high RPM to extract the best performance from the Civic. In contrast, Volkswagen's 2006 GTI 2.0T produces about 200 hp (149 kW) from 5,100 RPM to 6,000 RPM and a relatively flat torque band of 207 ft·lbf (281 N·m) from 1,800 to 5,000 RPM. This wide power delivery makes it easier for the driver to extract the vehicles best performance.


Power band considerations with a CVT vehicle

Because a CVT vehicle has the capability of keeping RPMs within the crest of the power band under acceleration, a peaky engine is optimal. Under full acceleration 100% of the available power can be extracted at all times. There is no shifting, and no moving out of the power band. This type of transmission is more efficient than others due to power band issues mentioned previously, but is not favored by many due to the lack of apparent power. Drivers are accustomed to the sudden lurch off the line and the shifting of the transmission. Though these are only actions of less efficient transmission, some vehicle manufacturers have computerized such events in to the transmission to add to the perception of power and torque.


Non-Automotive Power Band Tuning

Engines for ships and aircraft are also generally designed with a narrow power band as these vehicles do not have to operate over a wide speed range. They instead reach their optimal operating speed and remain there for the duration of their trips. As a result, they benefit from tuning for peak power and efficiency in a narrow power band.

Exhaust gas recirculation

Exhaust gas recirculation (EGR) is a NOx (nitrogen oxide and nitrogen dioxide) reduction technique used in most gasoline and diesel engines.

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with inert gas, lowering the adiabatic flame temperature and (in diesel engines) reducing the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix lowering the peak combustion temperature. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures.


EGR in Spark-Ignited (SI) Engines

In a typical automotive SI engine, 5 to 15 percent of the exhaust gas is routed back to the intake as EGR (thus comprising 5 to 15 percent of the mixture entering the cylinders). The maximum quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in an SI engine can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. Contrary to popular belief, a properly operating EGR actually increases the efficiency of gasoline engines via several mechanisms:

* Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.

* Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.

* Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC, rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is relatively minor compared to the first two.

It also decreases the efficiency of gasoline engines via a few more mechanisms

* Reduced intake charge density. EGR tends to heat the intake charge. This means a bigger piston or stroke must be used to induct the same amount of fuel and air mixture. This results in a bigger end heavier engine.

* Reduced specific heat ratio. A lean intake charge has a higher specific heat ratio than an EGR mixture. A reduction of specific heat ratio reduces the amount of energy that can be extracted by the piston.

EGR is typically not employed at high loads because it would reduce peak power output, and it is not employed at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.


EGR in Diesel Engines

In modern diesel engines, the EGR gas is cooled through a heat exchanger to allow the introduction of a greater mass of recirculated gas. Unlike SI engines, diesels are not limited by the need for a contiguous flamefront; furthermore, since diesels always operate with excess air, they benefit from EGR rates as high as 50% (at idle, where there is otherwise a very large amount of excess air) in controlling NOx emissions.

Since diesel engines are unthrottled, EGR does not lower throttling losses in the way that it does for SI engines (see above). However, exhaust gas (largely carbon dioxide and water vapor) has a higher specific heat than air, and so it still serves to lower peak combustion temperatures; this aids the diesel engine's efficiency by reduced heat rejection and dissociation. There are trade offs however. Adding EGR to a diesel reduces the specific heat ratio of the combustion gases in the power stroke. This reduces the amount of power that can be extracted by the piston. EGR also tends to reduce the amount of fuel burned in the power stroke. This is evident by the increase in particulate emissions that corresponds to an increase in EGR. Particulate matter (mainly carbon) that is not burned in the power stroke is wasted energy. Stricter regulations on particulate matter(PM) call for further emission controls to be introduced to compensate for the PM emissions introduced by EGR. The most common is particulate filters in the exhaust system that result in reduce fuel efficiency. Since EGR increases the amount of PM that must be dealt with and reduces the exhaust gas temperatures and available oxygen these filters need to function properly to burn off soot, automakers have had to consider injecting fuel and air directly into the exhaust system to keep these filters from plugging up.

Diesel engine EGR valves can be electrical or pneumatically actuated with proportional control see examples GT EGR Valves


Implementation of EGR

Recirculation is usually achieved by piping a route from the exhaust manifold to the inlet manifold, which is called external EGR. A control valve (EGR Valve) within the circuit regulates and times the gas flow. Some engine designs perform EGR by trapping exhaust gas within the cylinder by not fully expelling it during the exhaust stroke, which is called internal EGR. A form of internal EGR is used in the rotary Atkinson cycle engine.

EGR can also be used by using a variable geometry turbocharger (VGT) which uses variable inlet guide vanes to build sufficient backpressure in the exhaust manifold. For EGR to flow, a pressure difference is required across the intake and exhaust manifold and this is created by the VGT.

Other methods that have been experimented with are using a throttle in a turbocharged diesel engine to decrease the intake pressure to initiate EGR flow.

Early EGR systems were relatively unsophisticated, utilizing manifold vacuum as the only input to an on/off EGR valve; reduced performance and/or drivability were common side-effects. However, modern systems utilizing electronic engine control computers, multiple control inputs, and servo-driven EGR valves typically improve performance/efficiency with no impact on drivability. In the past, a meaningful fraction of car owners disconnected their EGR systems. Some still do either because they believe EGR reduces power output, causes a build-up in the intake manifold in diesel engines, or because they feel the environmental intentions of EGR are misguided. Disconnecting an EGR system is usually as simple as unplugging an electrically operated valve or inserting a ball bearing into the vacuum line in a vacuum-operated EGR valve. In all cases, the EGR system will need to be operating normally in order to pass emissions tests.

Injection pump

An Injection Pump is the device that pumps fuel into the cylinders of a diesel engine or less typically, a gasoline engine. Traditionally, the pump is driven indirectly from the crankshaft by gears, chains or a toothed belt (often the timing belt) that also drives the crankshaft on overhead-cam engines (OHC). It rotates at half crankshaft speed in a conventional four-stroke engine. Its timing is such that the fuel is injected only very slightly before top dead-centre of that cylinder's compression stroke. It is also common for the pump belt on gasoline engines to be driven directly from the camshaft.

Because of the need for positive injection into a very high-pressure environment, the pump develops great pressure—typically 15,000 psi (100 MPa) or more on newer systems. This is a good reason to take great care when working on diesel systems; escaping fuel at this sort of pressure can easily penetrate skin and clothes, and be injected into body tissues with serious consequences.

Earlier diesel pumps used an in-line layout with a series of cam-operated injection cylinders in a line, rather like a miniature inline engine. The pistons have a constant stroke volume, and injection volume (ie, throttling) is controlled by rotating the cylinders against a cut-off port that aligns with a helical slot in the cylinder. When all the cylinders are rotated at once, they simultaneously vary their injection volume to produce more or less power from the engine. Inline pumps still find favour on large multi-cylinder engines such as those on trucks, construction plant, static engines and agricultural vehicles.

For use on cars and light trucks, the rotary pump or distributor pump was developed. It uses a single injection cylinder driven from an axial cam plate, which injects into the individual fuel lines via a rotary distribution valve. Later incarnations such as the Bosch VE pump vary the injection timing with crank speed to allow greater power at high crank speeds, and smoother, more economical running at slower revs. Some VE variants have a pressure-based system that allows the injection volume to increase over normal to allow a turbocharger or supercharger equipped engine to develop more power under boost conditions.

All injection pumps incorporate a governor to cut fuel supply if the crank speed endangers the engine - the heavy moving parts of diesel engines do not tolerate overspeeding well, and catastrophic damage can occur if they are over-revved.

Mechanical pumps are gradually being phased out in order to comply with international emissions directives, and to increase performance and economy. Alternatives include common rail diesel systems and unit direct injection systems. These allow for higher pressures to be developed, and for much finer control of injection volumes compared to mechanical systems.

Catalytic Converter Technical Details

The catalytic converter consists of several components:

1. The core, or substrate. In modern catalytic converters, this is most often a ceramic honeycomb, however stainless steel foil honeycombs are also used. The purpose of the core is to "support the catalyst" and therefore it is often called a "catalyst support". The ceramic substrate was invented by Rodney Bagley, Irwin Lachman and Ronald Lewis at Corning Glass for which they were inducted into the National Inventors Hall of Fame in 2002.

2. The washcoat. In an effort to make converters more efficient, a washcoat is utilized, most often a mixture of silicon and aluminium. The washcoat, when added to the core, forms a rough, irregular surface which has a far greater surface area than the flat core surfaces, which is desirable to give the converter core a larger surface area, and therefore more places for active precious metal sites. The catalyst is added to the washcoat (in suspension) before application to the core.

3. The catalyst itself is most often a precious metal. Platinum is the most active catalyst and is widely used. However, it is not suitable for all applications because of unwanted additional reactions and/or cost. Palladium and rhodium are two other precious metals that are used. Platinum and rhodium are used as a reduction catalyst, while platinum and palladium are used as an oxidization catalyst. Cerium, iron, manganese and nickel are also used, though each has its own limitations. Nickel is not legal for use in the European Union (due to nickel hydrate formation). While copper can be used, its use is illegal in North America due to the formation of dioxin.


Rich Burn Spark Ignition Engines

Catalytic converters are used on spark ignition (gasoline; liquified petroleum gas (LPG); flexible fuel vehicles burning varying blends of E85 and gasoline; compressed natural gas (CNG)) engines; and compression ignition (diesel) engines.

For spark ignition engines the most commonly used catalytic converter is the three-way converter, which works best used on engines equipped with closed-loop feedback fuel mixture control employing an oxygen (lambda) sensor. While a 3-way catalyst can be used in a open-loop system (and has been for years in the non-road engine market), NOx conversions tend to be less than stellar - and since World emissions regulations are primarily aimed at NOx reduction, open loop fuel systems are now obsolete. To keep the air fuel ratio at stoichiometric (14.7:1 for gasoline), closed loop fuel systems are either fuel injection or a carburetor equipped for feedback mixture control. Within that band, conversions are very high, sometimes approaching 100%. However, outside of that band, conversions tend to fall off very rapidly (see bell curve). Two-way converters have been abandoned on spark ignition engines, due to an inability to control NOx.

A three-way catalyst reduces emissions of CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxides) simultaneously when the oxygen level of the exhaust gas stream is below 1.0%, though performance is best at below 0.5% O2. Unwanted reactions, such as the formation of H2S (hydrogen sulfide) and NH3 (ammonia), can occur in the three-way catalyst. Formation of each can be limited by modifications to the washcoat and precious metals used. It is, however, difficult to eliminate these side products entirely.

For example, when control of H2S (hydrogen sulfide) emissions is desired, nickel or manganese is added to the washcoat - both substances act to block the adsorption of sulfur by the washcoat. H2S is formed when the washcoat has adsorbed sulfur during a low temperature part of the operating cycle, which is then released during the high temperature part of the cycle and the sulfur combines with HC. For "lean burn" spark ignition engines (e.g. compressed natural gas, or compressed natural gas with diesel fuel pilot injection), an oxidation catalyst is used in the same manner as in a compression ignition engine.

Recently, systems have used a separate early catalytic converter in the system to reduce startup emissions and burn off the hydrocarbons from the extra-rich mixture used in a cold engine. Also, upstream and downstream parts are now often separated in the system to provide an optimum temperature and space for extra oxygen sensors. The converter needs to be placed close enough to the engine to quickly reach operating temperature but far enough away to avoid heat damage.

Early three-way catalytic converters utilized an air tube between the first part of the converter (the NOx part) and the second part, which is virtually unchanged from earlier two-way catalytic converters. This tube was fed by either an air pump (derived from the earlier A.I.R. systems) or by a Pulse Air system. The extra oxygen was used to offset the less precise control of earlier systems by providing the oxygen for the catalyst's oxidizing reaction. The first section was still prone to difficulties on lean conditions with too much oxygen for the NOx reduction to be complete, but the second section always had oxygen available. These systems also commonly included an upstream air injector, either a modified A.I.R. system or another opening in the manifold, to add oxygen into the system to burn the extra-rich mixture used in a cold engine and to allow the additional burning to happen as close to the converter as possible to heat it up to operating temperature quickly.

Newer systems use several techniques to avoid the air tubes. They provide a constantly varying mixture that quickly cycles lean and rich mixtures to keep the first catalyst (NOx reduction) from becoming oxygen loaded and the second catalyst (CO oxidization) sufficiently oxidized, which is less of a concern due to the oxygen created in the first section. They also utilize several oxygen sensors to monitor the exhaust, at least one before the catalytic converter for each bank of cylinders, and one after the converter. Newer systems also often have several units mounted along the pipe to provide different functions rather than one monolithic system.


Diesel Engines

For compression ignition (i.e., Diesel) engines, the most commonly used catalytic converter is the diesel oxidation catalyst. The catalyst uses excess O2 (oxygen) in the exhaust gas stream to oxidize CO (Carbon Monoxide) to CO2 (Carbon Dioxide) and HC (hydrocarbons) to H2O (water) and CO2. These converters often reach 90% effectiveness, virtually eliminating diesel odor and helping to reduce visible particulates (soot), however they are incapable of reducing NOx as chemical reactions always occur in the simplest possible way, and the existing O2 in the exhaust gas stream would react first.

To reduce NOx on a compression ignition engine it is necessary to change the exhaust gas - two main technologies are used for this - selective catalytic reduction (SCR) and NOx (NOx) traps (or NOx Adsorbers).

Another issue for diesel engines is particulate (soot). This can be controlled by a soot trap or diesel particulate filter (DPF), as catalytic converters are unable to affect elemental carbon (however they will remove up to 90% of the soluble organic fraction). A clogging soot filter creates a lot of back pressure decreasing engine performance. However, once clogged, the filter goes through a regeneration cycle where diesel fuel is injected directly into the exhaust stream and the soot is burned off. After the soot has been burned off the regeneration cycle stops and injection of diesel fuel stops. This regeneration cycle will not affect performance of the engine.

All major diesel engine manufacturers in the USA (Ford, Caterpillar, Cummins, Volvo, MMC) starting January 1, 2007 are required to have a catalytic converter and a soot filter inline, as per a new DoT legislation.


Oxygen storage

In order to oxidize CO and HC, the catalytic converter also has the capability of storing the oxygen from the exhaust gas stream, usually when the air fuel ratio goes lean. When insufficient oxygen is available from the exhaust stream the stored oxygen is released and consumed. This happens either when oxygen derived from NOx reduction is unavailable or certain maneuvers such as hard acceleration enrich the mixture beyond the ability of the converter to compensate.

Catalyst poisoning and deactivation

Catalytic converters become ineffective in the presence of lead due to catalyst poisoning. Therefore, vehicles equipped with catalytic converters must only be run on unleaded gasoline, and it is this fact, as much as concerns about the possibly harmful effects of lead emissions, which caused the end of pump-available leaded gasoline in countries where catalytic converters have been in common use for many years. Leaded "race only" fuel is still used for non-catalyst vehicles in some countries where it is no longer legal for road use. Catalyst poisoning occurs when a substance in the engine exhaust coats the surface of the catalyst, preventing further exhaust access to the catalytic materials. Poisoning can sometimes be reversed by running the engine under a very heavy load for an extended period of time to raise exhaust gas temperature, which may cause liquefaction or sublimation of the catalyst poison. Common catalyst poisons are lead, sulfur, zinc, manganese, silicon and phosphorus.

Zinc, phosphorus and sulfur originate from lubricant antiwear additives such as ZDDP; sulfur and manganese primarily originate from fuel impurities or from additives such as Methylcyclopentadienyl Manganese Tricarbonyl (MMT), respectively. Silicon poisoning in automotive applications is the result of engine damage, such as a faulty cylinder head gasket or cracked casting, admitting silicate-containing coolant into the combustion chamber. In stationary engines silicon poisoning is more often caused by the use of "Landfill" gas as a fuel.

Removal of sulfur from a catalyst surface by running heated exhaust gases over the catalyst surface is often successful; however, removal of lead deposits in this manner is usually not possible because of lead's high boiling point. In particularly bad cases of catalyst poisoning by lead, the catalytic converter can actually become completely plugged with lead residue.

A variety of conditions may cause the catalyst to overheat (heat deactivation) and potentially to melt down. Some factors that can cause this are:

* lubricating oil in the exhaust system (caused by engine wear, or by damaged rings or valves)

* an engine misfire or ignition failure (causing unburnt fuel to enter the exhaust)

* a cracked exhaust valve (again, causing unburnt fuel in the exhaust)

Overly rich fuel mixtures are not usually a problem - there is too little unused oxygen for the exotherm to be large enough to cause damage. A slightly lean of stoichiometric mix is far more dangerous, as the oxygen level is elevated, allowing a very large exotherm, and many engine manufacturers design "rich excursions" as a catalyst protection measure in the engine control software. In the early days of catalyst-equipped cars, (primarily in the USA) before the advent of sophisticated engine management systems, it was necessary for fuel/air mixtures to be significantly richer than had hitherto been the case to allow the catalyst to work effectively. This contributed to the very poor fuel consumption figures achieved by such cars.

Engine misfires can overheat and destroy the converter as the excessive amounts of unburned fuel are broken down within it, especially when the engine is under heavy loads. Vehicles equipped with OBD-II diagnostic systems are designed to alert the driver of a misfire condition, along with other malfunctions, using the Malfunction Indicator Lamp or "Check Engine" light. If the misfire and engine load can produce heating severe enough to cause catalyst damage, the MIL will flash until the misfire or engine load is reduced.

Catalytic converter

A catalytic converter (colloquially, "cat" or "catcon") is a device used to reduce the toxicity of emissions from an internal combustion engine. First widely introduced on series-production automobiles in the US market for the 1975 model year to comply with tightening EPA regulations on auto exhaust, catalytic converters are still most commonly used in motor vehicle exhaust systems. Catalytic converters are also used on generator sets, forklifts, mining equipment, trucks, buses, trains, and other engine-equipped machines. A catalytic converter provides an environment for a chemical reaction wherein toxic combustion by-products are converted to less-toxic substances.



Functions


Three-way catalytic converters

A three-way catalytic converter has three simultaneous tasks:

1. Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O

These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running at the stoichiometric point. This is 14.7 parts oxygen to 1 part fuel, by weight, for gasoline (the ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels). When there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction. When there is excessive fuel, then the engine is running rich. The reduction of NOx is favoured, at the expense of CO and HC oxidation. If an engine could be held at the strict stoichiometric point for the fuel used, it is theoretically possible to reach 100% conversion efficiencies.

Since 1981, three-way catalytic converters have been at the heart of vehicle emission control systems in North American roadgoing vehicles and are also used on "Large Spark Ignition" engines. LSI engines are used in forklifts, aerial boom lifts, ice resurfacing machines and construction equipment. The converters used in these are three-way types designed to reduce combined NOx+HC emissions from 12 gram/BHP-hour to 3 gram/BHP-hour or less, per the Environmental Protection Agency (EPA) 2004 regulations. A further drop to 2 gram/BHP-hour of NOx+HC emissions is mandated in 2007 (note: NOx is the industry standard short form for nitric oxide (NO) and nitrogen dioxide (NO2) both of which are smog precursors. HC is the industry short form for hydrocarbons). The EPA intends to introduce emissions rules for stationary Spark Ignition engines, to take effect in January 2008.


Two-way catalytic converters

A two-way catalytic converter has two simultaneous tasks:

1. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
2. Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water: 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O

This type of catalytic converter is widely used on diesel engines to reduce hydrocarbon and carbon monoxide emissions. They also were used on spark ignition (gasoline) engines in USA market automobiles up until 1981, when they were replaced by three-way converters due to regulatory changes requiring reductions on NOx emissions.

Curiously, the regulations regarding hydrocarbons vary according to the engine regulated, as well as the jurisdiction. In some cases, "non-methane hydrocarbons" are regulated, while in other cases, "total hydrocarbons" are regulated. Technology for one application (to meet a non-methane hydrocarbon standard) may not be suitable for use in an application that has to meet a total hydrocarbon standard. Methane is more difficult to break down in a catalytic converter, so in effect a "non-methane hydrocarbon" standard can be considered to be looser. Since methane is a greenhouse gas, more interest is rising in how to eliminate emissions of it.

GDi History

Contrary to what is generally written, Mercedes was not the first company to use fuel injection, or direct injection, on a production gasoline powered car. Both the 1952 Goliath GP700, and Gotbrud Superior 600, used Bosch direct fuel injection. The 1955 Mercedes-Benz 300SL, the first sports car to use fuel injection, used direct injection. The Bosch fuel injectors were placed into the bores on the cylinder wall used by the spark plugs in other Mercedes-Benz six-cylinder engines (the spark plugs were relocated to the cylinder head). Later, more mainstream applications of fuel injection favoured less expensive indirect injection methods.

It was not until 1996 that gasoline direct injection reappeared on the market. Mitsubishi Motors was the first with a GDI engine in the Japanese market Galant/Legnum's 4G93 1.8 L straight-4, which it subsequently brought to Europe in 1997 in the Mitsubishi Carisma, although Europe's high-sulphur fuel led to emissions problems, and fuel efficiency was less than expected. It also developed the first six cylinder GDI powerplant, the 6G74 3.5 L V6, in 1997. Mitsubishi applied this technology widely, producing over one million GDI engines in four families by 2001, PSA Peugeot Citroën and Hyundai Motors both licensed Mitsubishi's GDI technology in 1999, the latter using the first GDI V8. DaimlerChrysler produced a special engine for 2000, offered only in markets with low sulphur fuel.

Although other companies have since developed gasoline direct injection engines, GDI (with a capitalised letter "I") remains a registered trademark of Mitsubishi Motors.

Later GDi engines have been tuned and marketed for their high performance. Volkswagen/Audi led the trend with their 2001 GDi engine, under the product name Fuel Stratified Injection (FSI). The technology, adapted from Audi's Le Mans racecars.

BMW followed with a GDi V12. This initial BMW system used low-pressure injectors and could not enter lean-burn mode, but the company introduced its second-generation High Precision Injection system on the updated N52 straight-6 in 2006. This system surpasses many others with a wider envelope of lean-burn time, increasing overall efficiency. PSA is cooperating with BMW on a new line of engines which will make its first appearance in the 2007 MINI Cooper S.

General Motors had planned to produce a full range of GDi engines by 2002, but so far only two such engines have been introduced — in 2004, a version of the 2.2 L Ecotec used by the Opel Vectra and in 2005, a 2.0 L Ecotec with VVT technology for the Pontiac Solstice GXP.

In 2004 Isuzu Motors produced the first GDi engine sold in a mainstream American vehicle. Standard on the 2004 Axiom and optional on the 2004 Rodeo. Isuzu claimed the benefit of GDi is that the vaporizing fuel has a cooling effect, allowing a higher compression ratio (10.3 to 1 versus 9.1 to 1) that boosts output by 20 horsepower and that 0-to-60 times drop from 8.9 to just 7.5 seconds, with the quarter-mile being cut from 16.5 seconds to 15.8 ticks.

Toyota's 2GR-FSE V6 will use a combination of direct and indirect injection in 2006. It uses two injectors per cylinder, a traditional port injector and a new direct injector.

Mazda uses their own version of direct injection in the Mazdaspeed 6 / Mazda 6 MPS, the CX-7 sport-ute, and the new Mazdaspeed 3. It is referred to as Direct Injection Spark Ignition.

EnviroFit, a non-profit corporation sponsored by Colorado State University, has developed direct injection retrofit kits for heavily polluting two-stroke motorcycles in a project to reduce sometimes deadly air pollution in Southeast Asia. The kits use a technology invented and developed by Orbital Corporation Limited of Australia. Orbital's technology injects a mixture of fuel and compressed air into the combustion chamber instead of injecting fuel only, the most common system in automobiles. The compressed mixture rapidly expands as it enters the combustion chamber, and this breaks up the fuel into very small droplets which are more completely and efficiently burned, compared to carburetor and other fuel systems. The Orbital Combustion Process reduces two-stroke fuel consumption by 35 percent, according to EnviroFit. The organization, composed mostly of present and former CSU students and staff, has begun installing the kits on the millions of two-stroke taxis (motorcycles with big sidecars) in The Philippines. EnviroFit says its OCP kits reduce carbon monoxide emissions by 76 percent, carbon dioxide by 26 percent, and hydrocarbon emissions by 89 percent. Orbital's OCP two-stroke system is used in Mercury's Optimax DFI outboard engines, in Tohatsu's TLDI DFI outboard engines, in Bombardier's SeaDoo personal watercraft, and in motorscooters manufactured by Aprilia, Piaggio, Peugeot, and Kymco. Research on using the OCP system in four-stroke engines is underway.

Gasoline direct injection

Gasoline direct injection or GDi is a variant of fuel injection employed in modern two-stroke and four stroke petrol engines. The gasoline or biobutanol is injected right into the combustion chamber of each cylinder, as opposed to conventional multi point fuel injection that happens in the intake manifold, or cylinder port injection in two-strokes.

GDi enables stratified charge (ultra lean burn) combustion for improved fuel efficiency and emission levels at low load. Further improving efficiency and high-load output-power, the engine power is governed by modulating fuel injection, like a diesel engine; as opposed to restricting intake airflow, like a conventional gas internal combustion engine.



Theory of operation

The major advantages of a GDi engine are increased fuel efficiency and high power output. This is achieved by the precise control over amount of fuel and injection timings which are varied according to the load conditions. In addition, there are no throttling losses when compared to a conventional fuel injected or carburated engine, which greatly improves efficiency (only in engines that are using no throttle plate). Basically, the engine management system continuously chooses between three different modes of combustion: ultra lean burn combustion, stoichiometric combustion, and high power output mode.

Each mode is characterized by air-fuel ratio, the amount of fuel in the air-fuel mixture; the stoichiometric ratio for petrol is 14.7 to 1 by weight, but in ultra lean mode, it could be as high as 65 to 1. These are leaner mixtures than those ever achieved in the conventional engines are desired because of reduced fuel consumption.

* Ultra lean combustion mode is effective under normal running conditions, when little acceleration is required. The fuel is not injected at the intake stroke but rather at the latter stages of the compression stroke, so that the small amount of air-fuel mixture is optimally placed just near the spark plug. This stratified charge is surrounded by mostly air which keeps the fuel away from the cylinder walls for lowest emissions. The combustion takes place in a toroidal cavity on the piston's surface. This technique enables the usage of ultra lean mixtures with very high air-fuel ratio, impossible with traditional carburetors or even intake port injection.

* Stoichiometric combustion mode is activated for moderate load conditions. In this mode, fuel is injected during the intake stroke. The air-fuel mixture is homogeneous with the stoichiometric rates necessary for the catalytic converter to remove a maximum of the major pollutants CO and NOx from the exhaust gas.

* In full power mode, the air-fuel mixture is homogeneous as well and contains the minimum mass of fuel over the amount required for stoichiometric that is possible to ignite without knocking out, as defined by the compression ratio of the engine and the mass of air in the combustion chamber. The fuel is injected during the intake stroke. This mode activates at high load conditions and provides maximum output and torque.

Direct injection can also be accompanied by traditional methods such as VVT and VLIM, which provide conventional control over airflow swirl patterns at stoichiometric and full power modes. Water injection or EGR can help reduce NOx emissions inevitable when burning ultra lean mixtures.

PCV valve

The Positive Crankcase Ventilation valve, or PCV valve, is a one-way valve that ensures continual refreshment of the air inside a gasoline internal combustion engine's crankcase.


Explanation

As an engine runs, the crankcase (containing the crankshaft and other parts) begins to collect combustion chamber gases which leak past the rings surrounding pistons and sealing them to the cylinder walls. These combustion gases are sometimes referred to as "blow by" because the combustion pressure "blows" them "by" the pistons. These gases contain compounds harmful to an engine, particularly hydrocarbons, which are just unburned fuel, as well as carbon dioxide. It also contains a significant amount of water vapor. If allowed to remain in the crankcase, or become too concentrated, the harmful compounds begin to condense out of the air within the crankcase and form corrosive acids and sludge on the engine's interior surfaces. This can harm the engine as it tends to clog small inner passages, causing overheating, poor lubrication, and high emissions levels. To keep the crankcase air as clean as possible, some sort of ventilation system must be present.


PCV system

The PCV valve is only one part of the PCV system, which is essentially a variable and calibrated air leak, whereby the engine returns its crankcase combustion gases. Instead of the gases being vented to the atmosphere, gases are fed back into the intake manifold, to re-enter the combustion chamber as part of a fresh charge of air and fuel. The PCV system is not a classical "vacuum leak." Remember that all the air collected by the air cleaner (and metered by the mass air flow sensor, on a fuel injected engine) goes through the intake manifold anyway. The PCV system just diverts a small percentage of this air via the breather to the crankcase before allowing it to be drawn back in to the intake tract again. It is an "open system" in that fresh exterior air is continuously used to flush contaminants from the crankcase and into the combustion chamber.

The system relies on the fact that, while the engine is running, the intake manifold's air pressure is always less than crankcase air pressure. The lower pressure of the intake manifold draws air towards it, pulling air from the breather through the crankcase (where it dilutes and mixes with combustion gases), through the PCV valve, and into the intake manifold.

The PCV system consists of:
1) The breather tube , and
2) The PCV valve.
The breather tube connects the crankcase to a clean source of fresh air, such as the air cleaner body. Usually, clean air from the air cleaner flows in to this tube and in to the engine after passing through a screen, baffle, or other simple system to arrest a flame front, to prevent a potentially explosive atmosphere within the engine crank case from being ignited from a back-fire in to the intake manifold. The baffle, filter, or screen also traps oil mist, and keeps it inside the engine.

Once inside the engine, the air circulates around the interior of the engine, picking up and clearing away combustion byproduct gases, including a large amount of water vapor, then exits through a simple baffle, screen or mesh to trap oil droplets before being drawn out through the PCV valve, and into the intake manifold.


PCV valve

The PCV valve connects the crankcase to the intake manifold from a location more-or-less opposite the breather connection. Typical locations include the opposite valve cover that the breather tube connects to on a V engine. A typical location is the valve cover(s), although some engines place the valve in locations far from the valve cover. The valve is simple, but actually performs a complicated control function. An internal restrictor (generally a cone or ball) is held in "normal" (engine off, zero vacuum) position with a light spring, exposing the full size of the PCV opening to the intake manifold. With the engine running, the tapered end of the cone is drawn towards the opening in the PCV valve, restricting the opening proportionate to the level of engine vacuum vs. spring tension. At idle, the intake manifold vacuum is near maximum. It is at this time the least amount of blow by is actually occurring, so the PCV valve provides the largest amount of (but not complete) restriction. As engine load increases, vacuum on the valve decreases proportionally and blow by increases proportionally. Sensing a lower level of vacuum, the spring returns the cone to the "open" position to allow more air flow. At full throttle, there is nearly zero vacuum. At this point the PCV valve is nearly useless, and most combustion gases escape via the "breather tube" where they are then drawn in to the engine's intake manifold anyway.


Operation

Should the intake manifold's pressure be higher than that of the crankcase (which can happen under certain conditions, such as an intake backfire), the PCV valve closes to prevent reversal of the exhausted air back into the crankcase again. This is where the positive comes from in the name. Positive is basically a synonym for one-way.

It is critical that the parts of the PCV system be kept clean and open, otherwise air flow will not be correct. A plugged or malfunctioning PCV system will eventually damage an engine. PCV problems are primarily due to neglect or poor maintenance, typically engine oil change intervals that are inadequate for the engine's driving conditions. A poorly-maintained engine's PCV system will eventually become contaminated with sludge, causing serious problems. If the engine's lubricating oil is changed with adequate frequency, the PCV system will remain clear practically for the life of the engine. However, since the valve is constantly changing its resistance to flow by opening and closing proportionally as one drives a car, it is subject to eventual wear out over time. Typical maintenance schedules for gasoline engines are to replace the PCV valve whenever spark plugs are replaced. The long life of the valve despite the harsh operating environment is due to the trace amount of oil droplets suspended in the air that flows through the valve. These droplets keep the valve lubricated.

Not all gasoline engines have PCV valves. Engines not subject to emission controls, such as certain off-road engines, retain road draft tubes. Dragsters use a scavenger system and venturi tube in the exhaust to draw out combustion gases and maintain a small amount of vacuum in the crankcase to prevent oil leaks on to the race track. Small gasoline 2-cycle engines use the crank case to compress incoming air. All blow by in these engines is burned in the regular flow of air and fuel through the engine. Many small 4-cycle engines such as lawn mower engines and small gasoline generators, simply use a draft tube connected to the intake, between the air filter and carburetor, to route all blow by back in to the intake combustion air. The higher operating temperature of these small engines has a side effect of preventing large amounts of water vapor and light hydrocarbons from condensing in the lube oil.

Outside flame ignitor

An outside flame ignitor was an early ignition device used in internal-combustion engines that used a flame outside the engine and a sliding port on the cylinder head. At the appropriate time in the compression cycle of the engine, the port would briefly be opened and closed allowing the fuel/air mixture in the cylinder to be ignited by the flame.

They had many problems, including partial loss of compression through the port when it opened and many mechanical problems with the mechanism that operated the port.

They were considered obsolete before 1911.

E85 Risks

Corrosion

E85 can cause damage, since prolonged exposure to high concentrations of ethanol may corrode metal and rubber parts in older engines (pre-1988) designed primarily for gasoline. The hydroxyl group on the ethanol molecule is an extremely weak acid, but it can enhance corrosion for some natural materials. For post-1988 fuel-injected engines, all the components are already designed to accommodate E10 (10% ethanol) blends through the elimination of exposed magnesium and aluminum metals and natural rubber and cork gasketed parts. Hence, there is a greater degree of flexibility in just how much more ethanol may be added without causing ethanol-induced damage, varying by automobile manufacturer. Anhydrous ethanol in the absence of direct exposure to alkali metals and bases is non-corrosive; it is only when water is mixed with the ethanol that the mixture becomes corrosive to some metals. Hence, there is no appreciable difference in the corrosive properties between E10 and a 50:50 blend of E10 gasoline and E85 (47.5% ethanol), provided there is no water present, and the engine was designed to accommodate E10. Nonetheless, operation with more than 10% ethanol has never been recommended by car manufacturers in non-FFVs. Operation on up to 20% ethanol is generally considered safe for all post-1988 cars and trucks.


Water contamination

In addition to corrosion, there is also a risk of increased engine wear for non-FFV engines that are not specifically designed for operation on high levels (i.e., for greater than 10%) of ethanol. The risk primarily comes in the rare event that the E85 fuel ever becomes contaminated with water. For water levels below approximately 0.5% to 1.0% contained in the ethanol, no phase separation of gasoline and ethanol occurs. For contamination with 1% or more water in the ethanol, phase separation occurs, and the ethanol-water mixture will separate from the gasoline. This can be observed by pouring a mixture of suspected water-contaminated E85 fuel in a clear glass tube, waiting roughly 30 minutes, and then inspecting the sample. If there is water contamination of above 1% water in the ethanol, a clear separation of ethanol-water from gasoline will be clearly visible, with the colored gasoline floating above the clear ethanol-water mixture.

For ethanol contaminated with larger amounts of water (i.e., approximately 11% water, 89% ethanol, equivalent to 178 proof ethanol), considerable engine wear will occur, especially during times while the engine is heating up to normal operating temperatures. For example, just after starting the engine, low temperature partial combustion of the water-contaminated ethanol mixture takes place and causes engine wear. This wear, caused by water-contaminated E85, is the result of the combustion process of ethanol, water, and gasoline producing considerable amounts of formic acid (HCOOH, also known as methanoic acid and sometimes written as CH2O2). In addition to the production of formic acid occurring for water-contaminated E85, smaller amounts of acetaldehyde (CH3CHO) and acetic acid (C2H4O2) are also formed for water-contaminated ethanol combustion. Of these partial combustion products, formic acid is responsible for the majority of the rapid increase in engine wear.

Engines specifically designed for FFVs employ soft nitride coatings on their internal metal parts to provide resistance to formic acid wear in the event of water contamination of E85 fuel. Also, the use of lubricant oil (motor oil) containing an acid neutralizer is necessary to prevent the damage of oil-lubricated engine parts in the event of water contamination of fuel. Such lubricant oil is required by at least one manufacturer of FFVs even to this day (Chrysler).

For non-FFVs burning E85 in greater than 23.5% E85 mixtures (20% ethanol), the remedy for accidentally getting a tank of water-contaminated E85 (or gasoline) while preventing excessive engine wear is to change the motor oil as soon as possible after either burning the fuel and replacing it with non-contaminated fuel, or after immediately draining and replacing the water-contaminated fuel. The risk of burning slightly water-contaminated fuel with low percentages of water (less than 1%) on a long commute is minimal; after all, it is the low temperature combustion of water contaminated ethanol and gasoline that causes the bulk of the formic acid to form; burning a slightly-contaminated mix of water (less than 1%) and ethanol quickly, in one long commute, will not likely cause any appreciable engine wear past the first 15 miles of driving, especially once the engine warms up and high temperature combustion occurs exclusively.

For those making their own E85, the risk of introducing water unintentionally into their homemade fuel is relatively high unless adequate safety precautions and quality control procedures are taken. Ethanol and water form an azeotrope such that it is impossible to distill ethanol to higher than 95.6% ethanol purity by weight (roughly 190 proof); regardless of how many times distillation is repeated. Unfortunately, this proof ethanol contains too much water to prevent separation of a mixture of such proof ethanol with gasoline, or to prevent the formation of formic acid during low temperature combustion. Therefore, when making E85, it becomes necessary to remove this residual water. It is possible to break the ethanol and water azeotrope through adding benzene or another hydrocarbon prior to a final rectifying distillation. This takes another distillation (energy consuming) step. However, it is possible to remove the residual water more easily, using 3 angstrom (3A) synthetic zeolite pellets to absorb the water from the mix of ethanol and water, prior to mixing the now anhydrous ethanol with gasoline in an 85% to 15% by volume mixture to make E85. This absorption process is also known as a molecular sieve. The benefit of using synthetic zeolite pellets is that they are essentially comparable to using a catalyst, in being reusable and in not being consumed in the process, and the pellets require only re-heating (perhaps on a backyard grill, in a solar reflector furnace, or with heated carbon dioxide gas collected and saved from the fermentation process) to drive off the water molecules absorbed into the zeolite. Research has also been done at Purdue University on using corn grits as a desiccant. Once the ground corn becomes water logged, the corn grits can be processed much as the zeolite pellets, at least for a number of drying cycles before the grits lose their effectiveness. Once this occurs, it is possible to run the now water-logged corn grits through the natural fermentation process and convert them into even more ethanol fuel.


Air/Fuel mixture problems

Running a non-FFV with a high percentage of ethanol will cause the air fuel mixture to be leaner than normal in carbureted or open loop fuel injection engines, and cause closed loop fuel injection systems to adjust for the increase in oxygen content of the fuel mixture. A lean mixture, when leaner than stoichiometric, is unlikely to cause heat related engine damage because temperature decreases quickly once there is a surplus of air during the combustion event. The surplus air cools the burn, and lowers the exhaust gas temperature. The effects of surplus oxygen on the catalytic converter may be undesirable, and if too lean the engine will display roughness in operation. If the percentage of ethanol used results in sustained operation in the range between stoichiometric and best power mixture, problems may develop. In this range, between peak exhaust gas temperature and approximately 50 degrees rich of peak, combustion temperatures are at the highest possible, and may exceed the design temperatures for the engine. Detonation margins are reduced, and if operation at elevated temperatures is allowed to persist over considerable periods of time, heat related damage to valves and pistons can occur.

Without in-depth knowledge of the engine's mixture control system and instrumentation to monitor exhaust gas temperature, cylinder head temperature, cylinder pressure, and/or exhaust oxygen content, it is difficult to know whether the engine is operating in the "red" zone, or an acceptable mixture zone. Closed loop fuel injection systems eliminate much of the risk. This is also why the check engine light will illuminate if you mix more than around 50% to 60% E85 by volume with your gasoline in a non-FFV. If this happens, just add more 87 octane regular grade gasoline as soon as possible to correct the problem. (Some premium blends contain up to 10% ethanol; to correct the problem as quickly as possible, always add regular grade gasoline, not premium grade gasoline.) These fuel/air mixture related problems will not happen in a properly-converted vehicle.

Expansion chamber

An Expansion chamber is an exhaust system used on a two-stroke cycle engine to enhance its power output by improving its volumetric efficiency. It makes use of the energy left in the burnt exhaust exiting the cylinder to aid the filling of the cylinder for the next cycle. It is the two-stroke equivalent of the tuned pipes (or headers) used on four-stroke cycle engines.


How it works

The high pressure gas exiting the cylinder initially flows in the form of a "wavefront" as all disturbances in fluids do. The exhaust gas pushes its way into the pipe which is already occupied by gas from previous cycles, pushing that gas ahead and causing a wave front. Once the gas flow itself stops, the wave continues on by passing the energy to the next gas down stream and so on to the end of the pipe. If this wave encounters any change in cross section or temperature it will reflect a portion of its strength in the opposite direction to its travel. For example a high pressure wave encountering an increase in area will reflect back a low pressure wave in the opposite direction. A high pressure wave encountering a decrease in area will reflect back a high pressure wave in the opposite direction. The basic principle is described in wave dynamics An expansion chamber makes use of this phenomenon by varying its diameter (cross section) and length to cause these reflections to arrive back at the cylinder at the desired times in the cycle.


There are three main parts to the expansion cycle.


Blowdown

When the descending piston first exposes the exhaust port on the cylinder wall, the exhaust flows out powerfully due to its own pressure without assistance from the expansion chamber and so the diameter/area over the length of the first portion of the pipe is constant or near constant with a divergence of 0 to 2 degrees which preserves wave energy. This section of the system is called the "head pipe" (the exhaust port length is considered part of the head pipe for measurement purposes). By keeping the head pipe diameter near constant, the energy in the wave is preserved because there is no expansion until needed later in the cycle. In any case the flow leaving the cylinder during most of the blowdown process is sonic or supersonic and therefore no wave could travel back into the cylinder against that flow.


Transfer

Once the exhaust pressure has fallen to near atmospheric level the piston uncovers the transfer ports. At this point energy from the expansion chamber can be used to aid the flow of fresh mixture into the cylinder. To do this the expansion chamber is increased in diameter so that the out going high pressure wave reflects a negative pressure wave back toward the cylinder. This negative pressure arrives in the cylinder during the transfer cycle and greatly increases the flow of fresh mixture into the cylinder and can even suck fresh mixture out into the headpipe. This part of the pipe is called the divergent (or diffuser) section and it diverges at 6 to 12 degrees. It may be made up of more than one diverging cone depending on requirements.


Port blocking

When the transfer is complete the piston is on the way back up on its compression stroke but the exhaust port is still open, an unavoidable problem with the two stroke design. To help prevent the piston pushing fresh mixture out the open exhaust port a strong high pressure wave from the expansion chamber is timed to arrive during the compression stroke. The port blocking wave is created by reducing the diameter of the chamber. This is called the convergent section (a.k.a baffle cone or section). The outgoing high pressure wave hits the narrowing convergent section and reflects back a high pressure wave to the cylinder which arrives in time to block the port during the compression stroke and can push back into the cylinder any fresh mixture drawn out into the head pipe. The convergent section is made to converge at 8 to 90 degrees depending on requirements.

Combined with the high pressure wave there is a general rise in pressure in the chamber caused by deliberately restricting the outlet with a small tube called the stinger. The stinger restricts flow out of the chamber to cause higher pressure during the compression cycle and empties the chamber during the compression/power stroke to ready it for the next cycle. The stingers length and inside diameter are selected to match the engines requirements. (The inside diameter has the greatest effect and so is the most sensitive of the two.)


Complicating Factors

The operation of expansion chambers in practice is not as straightforward as described above. Waves traveling back up the pipe encounter the divergent section in reverse and reflect a portion of their energy back out. Temperature variations in different parts of the pipe cause reflections and changes in the local speed of sound. Sometimes these secondary wave reflections can inhibit the desired goal of more power.

It is useful to keep in mind that although the waves traverse the entire expansion chamber over each cycle, the actual gasses leaving the cylinder during a particular cycle do not. The gas flows and stops intermittently and the wave continues on to the end of the pipe. The hot gasses leaving the port form a "slug" which fills the header pipe and remains there for the duration of that cycle. This causes a high temperature zone in the head pipe which is always filled with the most recent and hottest gas. Because this area is hotter, the speed of sound and thus the speed of the waves that travel theough it are increased. During the next cycle that slug of gas will be pushed down the pipe by the next slug to occupy the next zone and so on. The volume this "slug" occupies constantly varies according to throttle position and engine speed. It is only the wave energy itself that traverses the whole pipe during a single cycle. The actual gas leaving the pipe during a particular cycle was created two or three cycles earlier.

Expansion chambers almost always have turns and curves built into them to accommodate their fit within the engine bay. Gasses and waves do not behave in the same way when encountering turns. Waves travel by reflecting and spherical radiation. Turns causes a loss in the sharpness of the wave forms and therefore must be kept to a minimum to avoid unpredictable losses.

Calculations used to design expansion chambers take into account only the primary wave actions. This is usually fairly close but errors can occur due to these complicating factors.



How Expansion chambers are made

There are three main methods of fabricating expansion chambers.


Hand formed

Flat sheet metal is rolled into cones and round sections, which are then welded together section by section. Although time consuming, it is usually the method chosen for development of a new design due to its flexibility, accuracy and low tooling costs.


Hydroforming

Two flat representations of the required finished pipe are cut out of sheet metal. The edges of the two identical flat cutouts are welded together forming a sandwich. On one end of the pipe a fitting is welded and high-pressure water is pumped into the cavity between the sheets. The pressure inflates the flat sheet into its final rounded shape. This method can be quicker than hand forming and only slightly more costly in tooling, however it requires a number of trials before a finished design as accurate as hand formed or stamped can be produced. All curves must be made in a single plane so cutting apart and re-welding is often required but the final product can be as good as a stamped pipe if enough care is taken to be precise.


Stamping

Flat sheet metal is pressed between a male and female mold in the shape of the required pipe. Each half of the pipe is stamped this way and the two halves are welded together. Stamping requires expensive tooling and machinery and is used only for mass production.

(Note-Functionally, expansion chambers need not be round in cross section but in practice a round shape is the best acoustically and is the only shape which (at a reasonable weight) can withstand the intense vibration and pounding without cracking.)


Summary

All these events need to be synchronized with the engine port timings and speed. An expansion chamber “tuned” for 8,000 rpm will not deliver the proper wave timings at 4,000 or 11,000 rpm. In fact it is likely to incur a power loss outside its “tuned” range.

The length of the pipe determines at what time the waves arrive back at the cylinder. Longer pipes require more time for the waves to traverse and so will be tuned to a lower rpm than a shorter pipe. The shorter the pipe the higher the rpm it is tuned to.

The rate of convergence/divergence of the cones determines the duration of the wave returned. A gentle taper give a long duration but weaker return wave while a steeper taper gives a short but strong return wave. The longer the wave, the broader the RPM range at which it is useful. This extra power band width is at the sacrifice of peak torque.

The diameter of the center or dwell section determines the ratio of scavenging suction to port blocking pressure as well as the over all energy recovery. The resulting volume determines the maximum pressure rise with large volumes giving less pressure rise. The fatter the pipe the harder it sucks but the weaker the blocking pressure. Thinner pipes will scavenge less but block the port very strongly. The optimum diameter is related to compression ratio, the quality of the transfer port layout and its scavenging efficiency.

A variety of devices are used to try to extend the tuned range of the expansion chamber. Pipes that slide like a trombone adjust the timing to match the rpm changes of the running engine. Devices that control the exhaust port timing to vary blowdown duration as well as extending the tuned range of the expansion chamber. Valves that open at certain speeds to absorb or dump waves arriving at undesirable times.

Another approach to altering the tuned RPM of an expansion chamber is to alter the speed of the pressure waves inside the exhaust pipe. The speed at which pressure waves travel is greatly affected by temperature: higher temperature means faster wave speed. As a result, expansion chambers can be retuned for higher-than-design RPM resonance, by increasing the average temperature of the exhaust gases inside the pipe. Techniques to achieve this increase in gas temperature can include: insulating the pipe (thermal wrap), restricting flow from the pipe (smaller stinger diameter), or by retarding the ignition timing at the correct RPM (a later burn allows more heat to escape into the pipe).

Conversely, a pipe can be retuned to work at a lower-than-design RPM range by reducing the temperature of the exhaust gases. Injecting water or a water-alcohol mix into the headpipe of an expansion chamber can reduce temperatures significantly, enough to lower the tuned RPM of an exhaust system by as much as 1500- 2000 RPM. The heat absorbed as the liquid changes into a gas is responsible for the drop in temperature. As a result, the two stroke exhaust can be tuned to stay "on the pipe" over a remarkably wide RPM range, if the designer takes advantage of all the tools available.