Continuously variable transmission

The continuously variable transmission (CVT) is a transmission in which the ratio of the rotational speeds of two shafts, as the input shaft and output shaft of a vehicle or other machine, can be varied continuously within a given range, providing an infinite number of possible ratios.

The continuously variable transmission should not be confused with the power split transmission (PST), as used in the Toyota Prius and other hybrid vehicles that use two or more inputs with one output, despite some similarities in their function.

A CVT need not be automatic, nor include zero or reverse output. Such features may be adapted to CVTs in certain specific applications.

Other mechanical transmissions only allow a few different discrete gear ratios to be selected, but the continuously variable transmission essentially has an infinite number of ratios available within a finite range, so it enables the relationship between the speed of a vehicle engine and the driven speed of the wheels to be selected within a continuous range. This can provide better fuel economy than other transmissions by enabling the engine to run at its most efficient speeds within a narrow range.

CVT transmissions have been refined over the years and are much improved from their origins.



Types


Infinitely Variable Transmission (IVT)

A specific type of CVT is the infinitely variable transmission (IVT), which has an infinite range of input/output ratios in addition to its infinite number of possible ratios; this qualification for the IVT implies that its range of ratios includes a zero output/input ratio that can be continuously approached from a defined "higher" ratio. A zero output implies an infinite input, which can be continuously approached from a given finite input value with an IVT. Low gears are a reference to low ratios of output/input which have high input/output ratios that are taken to the extreme with IVTs, resulting in a "neutral", or non-driving "low" gear limit. Most continuously variable transmissions are not infinitely variable.

Most (if not all) IVTs result from the combination of a CVT with an epicyclic gear system (which is also known as a planetary gear system) that facilitates the subtraction of one speed from another speed within the set of input and planetary gear rotations. This subtraction only needs to result in an continuous range of values that includes a zero output; the maximum output/input ratio can be arbitrarily chosen from infinite practical possibilities through selection of extraneous input or output gear, pulley or sprocket sizes without affecting the zero output or the continuity of the whole system. Importantly, the IVT is distinguished as being "infinite" in its ratio of high gear to low gear within its range; high gear is infinite times higher than low gear. The IVT is always engaged, even during its zero output adjustment.

The term "Infinitely Variable Transmission" does not imply reverse direction, disengagement, automatic operation, or any other quality except ratio selectabilty within a continuous range of input/output ratios from a defined minimum to an undefined, "infinite" maximum. This means continuous range from a defined output/input to zero output/input ratio.


Ratcheting CVT

The Ratcheting CVT is a transmission that relies on static friction and is based on a set of elements that successively become engaged and then disengaged between the driving system and the driven system, often using oscillating or indexing motion in conjunction with one-way clutches or ratchets that rectify and sum only "forward" motion. The transmission ratio is adjusted by changing linkage geometry within the oscillating elements, so that the summed maximum linkage speed is adjusted, even when the average linkage speed remains constant. Power is transferred from input to output only when the clutch or ratchet is engaged, and therefore when its locked into a static friction mode where the driving & driven rotating surfaces momentarily rotate together without slippage.

These CVT transmissions can transfer substantial torque because their static friction actually increases relative to torque throughput, so slippage is impossible in properly designed systems. Efficiency is generally high because most of the dynamic friction is caused by very slight transitional clutch speed changes. The drawback to ratcheting CVT's is vibration caused by the successive transition in speed required to accelerate the element which must supplant the previously operating & decelerating, power transmitting element. An Infinitely Variable Transmission (IVT) that is based on a Ratcheting CVT and subtraction of one speed from another will greatly amplify the vibration as the IVT output/input ratio approaches zero.

Ratcheting CVT's are distinguished from Variable Diameter Pulleys (VDP's) and Roller-based CVT's by being static friction-based devices, as opposed to being dynamic friction-based devices that waste significant energy through slippage of twisting surfaces.


Variable-diameter pulley (VDP)

This type of CVT uses pulleys, typically connected by a rubber-covered metal or laminated steel belt. A chain may also be used. A large pulley connected to a smaller pulley with a belt or chain will operate in the same manner as a large gear meshing with a smaller gear. Typical CVTs have pulleys formed as pairs of opposing cones. Moving the cones in and out has the effect of changing the pulley diameter since the belt or chain must take a large-diameter path when the conical pulley halves are close together. This motion of the cones can be computer-controlled and driven, for example by a servo motor. However, in the light-weight VDP transmissions used in automatic motorscooters and light motorcycles, the change in pulley diameter is accomplished by a variator, an all-mechanical system that uses weights and springs to change the pulley diameters as a function of belt speed. In higher power types, for example that produced by Van Doorne's Transmissie (part of the Bosch Group), an oil-cooled laminated steel belt is used.

In the case of a chain the links bear on the pulleys via tapered sides on the links. Some such transmissions have been designed to transmit the forces between pulleys using compressive (pushing) rather than traction (pulling) forces. The chain driven transmission designed by LuK and VAG/Audi uses a special lubricant which undergoes a phase change under extreme pressure to form a glassy solid, enabling the chain to transmit considerable torque through small contact surfaces.


Roller-based CVT

(marketed as the Traction CVT, Extroid CVT, Nuvinci CVP, or IVT)

Consider two almost-conical parts, point to point, with the sides dished such that the two parts could fill the central hole of a torus. One part is the input, and the other part is the output (they do not quite touch). Power is transferred from one side to the other by one or more rollers. When the roller's axis is perpendicular to the axis of the almost-conical parts, it contacts the almost-conical parts at same-diameter locations and thus gives a 1:1 gear ratio. The roller can be moved along the axis of the almost-conical parts, changing angle as needed to maintain contact. This will cause the roller to contact the almost-conical parts at varying and distinct diameters, giving a gear ratio of something other than 1:1. Systems may be partial or full toroidal. Full toroidal systems are the most efficient design while partial toroidals may still require a torque converter (e.g., Jatco "Extroid"), and hence lose efficiency.


Hydrostatic CVT

Hydrostatic transmissions use a variable displacement pump and a hydraulic motor. All power is transmitted by hydraulic fluid. These types can generally transmit more torque, but are very sensitive to contamination. Some designs are also very expensive. However, they have the advantage that the hydraulic motor can be mounted directly to the wheel hub, allowing a more flexible suspension system and eliminating efficiency losses from friction in the drive shaft and differential components. This type of transmission has been effectively applied to expensive versions of light duty ridden lawn mowers, garden tractors and some heavy equipment. Agricultral machinery including foragers and comblins butr not anything that works the ground beacause the transmission cannot transmit enough torque.


Hydristor IVT

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The Hydristor torque converter is a true IVT in that the front unit connected to the engine can displace from zero to 27 cubic inches per revolution forward and zero to -10 cubic inches per revolution reverse. The rear unit is capable of zero to 75 cubic inches per revolution. The common "kidney port" plate between the two sections communicates the hydraulic fluid under pressure and suction return in a "serpentine-torodial" flow path between the two Hydristor internal units. The IVT ratio is determined by the ratio of input displacement to output displacement. Therefore, the theoretical range of Hydristor IVT ratios is 1/infinity to +-infinity/1 but real-world ratios are constrained by physics.


Simkins' Ratcheting CVT

This transmission is an example of a Ratcheting CVT, prototyped as a bicycle transmission, protected under U.S. Patent #5516132. The input is the crank with a round hub integrated with it, and an array of twelve arms that are pivotally mounted to pins in the hub circle. Each arm has a pinion gear mounted on a one way clutch that allows only clockwise rotation of the pinion relative to the arm. All of these pinions are engaged with a large ring gear that is integrated with the chainwheel as the output, and the ring gear/chainwheel assembly is mounted to a mechanism that enables it to be adjusted from a position of concentricity with the crank hub to various amounts of eccentricity with the crank hub. Adjustment of this eccentricity variably changes the output/input ratio from 1:1 to 2.6:1 as the ring gear/sprocket assembly is moved from a position concentric with the crank hub to an eccentric position.

The eccentricity control mechanism is connected to a spring that pushes the transmission into its eccentric high gear position shown in the picture. The largest spread of the arms is indicative of the gear ratio because the spreading arms are the only arms whose pinions (and one-way clutches) are locked and driving the ring gear/chainwheel assembly. Strong pedaling torque causes this mechanism to react against the spring, moving the ring gear/chainwheel assembly toward a concentric, lower gear position. When the pedaling torque relaxes to lower levels, the transmission self-adjusts toward higher gears, accompanied by an increase in transmission vibration that produces a foot massage! This transmission behaves according to the definition of a Ratcheting CVT.


Anderson A+CVT

Anderson A+CVT is a technology invented by Larry Anderson, under US patents 6,575,856 and 6,955,620. Two parallel cones have "floating sprocket bars" mounted in longitudinal grooves around the circumference of each cone.

A specially-designed chain meshes with the floating sprocket bars, and is free to slide along the length of cones, changing the gear ratio at each point. The floating sprocket bars make the A+CVT positive-drive, non-friction-dependent. Another advantage of the A+CVT is the simplicity of its design, as it consists of far fewer components than other transmissions. The technology is also adaptable to a variable diameter pulley-type CVT, by mounting the floating sprocket bars on the inner face of the pulley sheaves. A few critics[attribution needed] have speculated that noise could be a problem with the A+CVT. However, Anderson has said that he believes noise will be no more of an issue with the A+CVT than with other transmissions, as the A+CVT will be lubricated and encased in a housing.


Advantages and drawbacks

Compared to hydraulic automatic transmissions:

* CVTs can smoothly compensate for changing vehicle speeds, allowing the engine speed to remain at its level of peak efficiency. They may also avoid torque converter losses. This improves both fuel economy and exhaust emissions. However, some units (e.g., Jatco "Extroid") also employ a torque converter. Fuel efficiency advantages as high as 20% over four-speed automatics can be obtained.

* CVTs have much smoother operation. This can give a perception of low power, because many drivers expect a jerk when they begin to move the vehicle. The satisfying jerk of a non-CVT transmission can be emulated by CVT control software though, eliminating this marketing problem.

* Since the CVT keeps the engine turning at constant RPMs over a wide range of vehicle speeds, pressing on the accelerator pedal will make the car move faster but doesn't change the sound coming from the engine as much as a conventional automatic transmission gear-shift. This confuses some drivers and again, leads to a mistaken impression of a lack of power.

* Most CVTs are simpler to build and repair.

* CVT torque handling capability is limited by the strength of their belt or chain, and by their ability to withstand friction wear between torque source and transmission medium for friction-driven CVTs. CVTs in production prior to 2005 are predominantly belt or chain driven and therefore typically limited to low powered cars and other light duty applications. More advanced IVT units using advanced lubricants, however, have been proven to support any amount of torque in production vehicles, including that used for buses, heavy trucks, and earth moving equipment.

Close-ratio transmission

A close-ratio transmission is a transmission in which there is a relatively little difference between the gear ratios of the gears. Consequently, note that the word close implies "near", not "shut". The gear ratio numbers are in a smaller numeric range, hence closer together.

In the context of close-ratio transmissions, a transmission with large differences between gears is termed "wide-ratio". Close-ratio vs. wide-ratio are relative terms, with no standardization. Therefore, a transmission that a manufacturer terms close-ratio when paired with a V8 engine with a wide power band may be termed wide-ratio when paired with a high-revving straight-4.


Comparison with ordinary transmission

Gear	"Typical" stock 5 speed	"Typical" close-ratio 5 speed for same vehicle
1st	3.25	2.60
2nd	1.90	1.66
3rd	1.20	1.35
4th	1.00	1.15
5th	0.80	1.00

Note how the ordinary 5 speed transmission has a high 5th gear. This is for fuel-efficient cruising with relatively low RPMs at freeway speeds. Such a high gear is not necessarily useful in a race situation. In order for the car's transmission be in that gear and simultaneously for its engine to be in its high-power RPM range, the absolute speed of the vehicle may simply be too great. In other words, the closeness of the ratios of a close-ratio transmission may be obtained by compressing both ends: raising the lower gear ratios, and lowering the higher ones.


Application

A close-ratio type of transmission is designed to allow an engine to remain in a relatively narrow operating speed. Alternately, a wide-ratio transmission requires the engine to operate over a greater speed range, but requires less shifting and allows a wider range of output speeds. Close-ratio transmissions are generally offered in sports cars, in which the engine is tuned for maximum power in a narrow range of operating speeds and the driver can be expected to enjoy shifting often to keep the engine in its power band.

A race is driven at high speed, close to the top speed that is achievable with the car's engine power. The speed has to be reduced for taking turns of various curvatures. Within this range of racing speeds, it may be useful to have many gears to choose from in order to always operate near the maximum engine speed.

Race cars do not have to deal with stop-and-go traffic, intersections, frequent stops, parallel parking, or climbing steep hills at slow speed. Race cars are also not called upon to perform fuel-efficient cruising at low RPM. Consequently, it makes little sense to have gears that support these driving situations at the expense of insufficient gear ratio variety for the intended use, and for this reason, a conventional 5-speed transmission would effectively offer too few useful gears in the race situation. After being used briefly at the very start of the race, the first two gears would never be used again. Moreover, the highest gear could even be too high to get the car into its top speed on a long, straight section of the course. The highest gear should be such that it allows the top speed of the car to coincide with the engine's peak power RPM, where the engine power is just sufficient to fight air drag and other sources of impedance.

The wide gear ratios may also simply be too far apart for fast acceleration, due to each successive gear dropping the engine RPM too low. Suppose that a given engine's power band lies between 7000 and 8000 RPM. Shifting up from a 1.20 gear to a 0.9 gear drops the original RPM by 25% (reducing it to 0.75 of the original rate). That is enough of a drop to take the engine out of its power RPM zone. For instance, if the shift is executed at 8000 RPM, the engine falls to about 6200 RPM, where it will generate a lot less power. The climb from 6200 will be a slow, labored acceleration. By contrast, shifting up from a 1.15 gear to a 1.0 gear represents only a 13% drop in engine revolution speed. Executed at 8000 RPM, the shift will achieve nearly 7000 RPM, just at the low end of the example engine's power band, allowing the car to continue accelerating quickly.


Pseudo-close-ratio transmissions

One way to obtain some of the benefits of a close-ratio transmission, without the compromises, is simply to cram more gears into the transmission. In fact, some six-speed gearboxes available in consumer vehicles are labelled as "close-ratio".

Whether a six speed transmission can be legitimatelly called "close-ratio" depends on whether, compared to a five speed model, it adds an extra high overdrive gear for leisurly freeway cruising, or whether it keeps the top gear about the same as in a comparable 5-speed model, and rather distributes more closely spaced ratios among the lower gears.

To simultaneously capture the advantages of a regular five-speed wide-ratio transmission as well as a five-speed close-ratio transmission, it can be argued that seven gears are required (like current Formula One cars and BMW M5). Six are too few, because a low first gear and a tall, smooth-cruising overdrive gear leave only four remaining gears. If truly close ratios are assigned to these, then second gear will be too tall.

Belt (mechanical)

Belts are used to mechanically link two or more rotating items. They may be used as a source of motion, to transmit power at up to 98% efficiency between two points, or to track relative movement.

As a source of motion, a conveyor belt is one application where the belt is adapted to continually carry a load between two points. A belt may also be looped (or crossed) between two points so that the direction of rotation is reversed at the other point.

Power transmission is achieved by specially designed belts and pulleys. The demands on a belt drive transmission system are large and this has led to many variations on the theme.

The earliest was the flat belt, used with line shafting. It is a simple system of power transmission that was well suited to its time in history. The Industrial Revolution soon demanded more from the system, as flat belt pulleys need to be carefully aligned to prevent the belt from slipping off. The flat belt also tends to slip on the pulley face when heavy loads are applied. In practice, such belts were often given a half-twist before joining the ends (forming a Möbius strip), so that wear was evenly distributed on both sides of the belt.

Round belts are a circular cross section belt designed to run in a pulley with a circular (or near circular) groove. They are for use in low torque situations and may be purchased in various lengths or cut to length and joined, either by a staple, gluing or welding (in the case of polyurethane). The early sewing machines utilized a leather belt, joined either by a metal staple or glued, to great affect.

Vee belts (also known as v-belt or wedge rope) are an early solution that solved the slippage and alignment problem. The V-belt was developed in 1917 by John Gates of the Gates Rubber Company. The "V" shape of the belt tracks in a mating groove in the pulley (or sheave), with the result that the belt cannot slip off. The belt also tends to wedge into the groove as the load increases — the greater the load, the greater the wedging action — improving torque transmission and making the vee belt an effective solution. They can be supplied at various fixed lengths or as a segmented section, where the segments are linked (spliced) to form a belt of the required length. For high-power requirements, two or more vee belts can be joined side-by-side in an arrangement called a multi-V, running on matching multi-groove sheaves. The strenght of these belts is obtained by reinforcements with fibers like steel, polyester or aramid (e.g. Twaron).

Timing belts, (also known as Toothed, Notch or Cog) belts are a positive transfer belt and can track relative movement. These belts have teeth that fit into a matching toothed pulley. When correctly tensioned, they have no slippage and are often used to transfer direct motion for indexing or timing purposes (hence their name). Camshafts of automobiles and stepper motors often utilize these belts.

Timing belts with a helical offset tooth design are available. The helical offset tooth design forms a chevron pattern and causes the teeth to engage progressively. The chevron pattern design is self-aligning. The chevron pattern design does not make the noise that some timing belts make at idiosyncratic speeds.

Belts normally transmit power only on the tension side of the loop. However, designs for continuously variable transmissions exist that use belts that are a series of solid metal blocks, linked together as in a chain, transmitting power on the compression side of the loop.

Super Select (Active-Trac)

Super Select is the brand name of a four-wheel drive system produced by Mitsubishi Motors, used worldwide except for North America, where it is known as Active-Trac. It was first introduced in 1991 with the then-new second generation of the Mitsubishi Pajero.

The system offers a choice of four rear- or four-wheel driving modes, selected using a lever mounted alongside the gear shift, and can be changed while the vehicle is in motion. In 2H mode the front axle is disconnected and the vehicle is rear-wheel drive. Reduced frictional losses in the powertrain mean that fuel economy improves while noise levels are reduced. 4H is a part-time four-wheel drive mode using a viscous coupling unit (VCU) and center differential to direct drive to the front wheels when the rear axle loses traction, and is capable of handling a wide variety of road conditions and speeds. 4HLc locks the center differential to provide extra traction for sandy, snowy or poorly surfaced roads in "high range" mode, while 4LLc, the "low range" mode, also offers a much lower gearing, providing the maximum amount of traction. Changing between 4HLc and 4LLc is only possible with the vehicle stationary.

The system is used on Mitsubishi's Pajero iO mini SUV, while its larger Pajero, Challenger, Triton and Delica models use a more complex system dubbed Super Select II (SS4-II). In most respects the two are the same, although the torque-split in SS4-II is 33/67 front/rear, meaning two thirds of the torque is channelled to the rear axle. In Super Select (SS4i) the torque-split is an equal 50/50. SS4-II also offers an option to lock the rear differential, offering greater traction to the rear axle.

Corvair engines Trivia and arcana

Many Corvair engine fans acquired a second life after the demise of their engines, mounted bottom side out on the outside of the wheels of Corvettes involved in road-racing, in order to pull air through the brakes and keep them cool. Lightweight and cheap, they were perfectly sized.

The single carburetor on each head of the two carburetor engine was not mounted symmetrically in the center of the intake manifold, where it might be intuitively placed, but offset from the center, between the middle and end cylinders. Although sometimes erroneously cited as an engineering error, this was in fact an example of clever attention to detail; had the carburetor been placed in the center of the manifold, the center cylinder would have received a significantly greater air/fuel charge then either end cylinder. Instead, the carburetor was situated so that the firing order required the air flow to reverse itself when filling either of the nearer cylinders, whereas the airflow to the far cylinder was merely an extension of the airflow to the center cylinder, which was just prior in the firing order. This allowed for a more balanced filling of the three cylinders, and smoother operation.

High performance parts manufacturer Edelbrock made available a set of larger bore aluminum cylinder barrels (with cast iron liners to withstand wear); when combined with their aluminum pushrods, the rate of thermal expansion of all parts of the valve train became compatible, so that solid valve lifters could be used, rather than the hydraulic lifters required by the stock cast iron cylinders. This in turn allowed the engine to run to higher RPMs; in conjunction with the increased torque resulting from the increase in cylinder bore, this resulted in a substantially more powerful engine.

In addition, "stroker" crankshafts with longer stroke were quickly made available for the original engine. When Chevrolet increased the stroke of the stock engine, however, there was no longer room to increase it any further.

Immediately after the car became available with the original two carburetor engine, a number of manufacturers began to sell conversion kits for attachment of four carburetors, with either two stock carburetors, two of the ubiquitous Stromberg 97 carburetors, or a Rochester two barrel carburetor for each bank of cylinders. The means of attachment varied from simple two into one adapters, to machining off the entire top surface of the intake manifold (cast as part of the head), enlarging the internal passages of the manifold, and attaching a new upper surface incorporating the appropriate mounting pads for the new carburetors. Similarly, aftermarket manufacturers provided several means of supercharging the original engine, including belt driven centrifugal, axial flow, or rotary vane type compressors. Chevrolet, seeing the marketing opportunity available in these aftermarket options, of course went on to offer its own four carburetor and turbocharged versions.

Corvair engines swapped into Volkswagens

Initially, the cooling fans were designed with a twist to the vanes, so that they were only efficient when rotating in the correct direction. Early on, however, the vanes on the fan became vertical and radial, so that the fan functioned identically in either rotation. Whatever the reason for this change, one effect was that the engine could easily be configured to run in the direction opposite from stock. This proved useful for those who swapped the engine into Volkswagen Beetles and dune buggies, since the Corvair engine's normal direction of rotation was opposite to that of the Volkswagen (and most other automobiles). Otherwise, the ring gear of the Volkswagen differential had to be flipped over by 180 degrees to allow the transmission's forward and reverse directions to be correct.

This swap was fairly common at the time, with the Corvair engine serving to give a power boost to Volkswagen Beetles, dune buggies, and Karmann Ghias. Excessively vigorous use of first gear would break the transaxle (the prudent driver would avoid first gear altogether), and the engine cover of the Karmann Ghia would not close completely with a Corvair engine in place, but otherwise the swap was relatively problem free, as such things go.

Chevrolet Corvair engine Problems

The Corvair engine design was so unique that good dealer service and maintenance was spotty. Mechanics, unused to the aluminum head and crankcase, would frequently overtighten threaded fasteners and spark plugs, stripping the threads out of the aluminum, requiring extensive repair.

Due to the greater thermal expansion of aluminum, hydraulic valve lifters were used to maintain correct lash as the engine expanded. These were trouble free and did not require periodic adjustment. Tuning issues related to the dual (or quadruple) carbs in non-turbocharged Corvairs sometimes led to erroneous diagnosis of valve issues in Corvairs- in fact, the Corvair had top quality valve materials in all models and valve jobs were almost never required. In fact, the valve train in most engines usually functioned perfectly for the life of the car.

Early engines were subject to occasional failures of the head gasket, between the heads and the cylinder barrels; this was addressed in later models by increasing the width of the sealing area and redesigning the gasket material and cross section, eliminating any issues.

The large cooling fan located on top of the engine required the fan belt to bend from the vertical plane of the crankshaft to the horizontal plane of the fan, causing additional stress. Chevrolet engineers designed a unique fan belt, which many owners and dealers replaced with an inappropriate design. The correct fan belt, properly installed to proper tension, worked well, while other belts even of proper size installed loose or tight would break frequently, giving the engine fan and belt design an undeserved bad reputation. Since failure of the cooling fan on an air-cooled engine leads to immediate overheating much more quickly than in a water-cooled engine (within 15 seconds at the high RPMs when the belts were likely to fail), mechanically inclined owners would routinely carry a spare belt and the 9/16 inch box wrench needed to change the belt, in addition to adding a large and eye catching warning light in parallel with the normally sized factory generator/alternator warning light. Aftermarket manufacturers made available differently sized pulleys which reduced the fan speed to 1.3 or 1.2 times engine speed, rather than the stock 1.5; this reduced the tendency to throw or break a fan belt for engines which spent most of their time at higher RPMs.

The pushrods were located below the cylinders, each in a separate metal tube between the crankcase and the head; these tubes also served to return oil from the head to the crankcase, and were fitted with neoprene O-rings at each end. After a short time, the neoprene exposed to the intense heat of the head lost resilience and developed a tendency to leak oil which became characteristic of Corvairs; unfortunately, since engine cooling air was diverted to the interior heater, this caused an unpleasant odor. Improved elastomer O-rings with much greater durability became available from aftermarket suppliers.

To address fuel slosh and cut-out issues in very hard cornering, some owners acquired an aftermarket kit to rotate the carburetors through ninety degrees and attach the now colinear throttle shafts of the two carburetors on each side together. However, this also eliminated the progressive feature of the stock carburetor linkage, so that performance could not be optimized both at low to midrange rpm and at high rpm.

Other owners replaced the four single-barrel carburetors with a single four-barrel carburetor, centrally mounted on a manifold with four long arms that attached to the original carburetor mounting pads on the heads. While this caused the carburetor and manifold to be slow to warm up to operating temperature and therefore caused problems with flooding and cold temperature operation, it eliminated linkage problems, simplified tuning the carburetor, and provided access to the large variety of four-barrel carburetors available on the market. This modification was especially ill-suited to models with Powerglide.

A factor which would have, in itself, led to the demise of the air cooled engine design was the rapid and relatively large temperature variation of the air-cooled engine with variations in load and rpm; this would have made meeting the upcoming emissions requirements of the 1970s difficult. Engine temperatures on lower performance Corvairs with the AIR system were comparable to the Turbocharged models in some situations- head temperatures under full throttle could exceed 600F.

Chevrolet Corvair engine

The Chevrolet Corvair engine was a flat-6 (or boxer engine) piston engine used exclusively in the 1960s Chevrolet Corvair automobile. It was a highly unusual engine for General Motors: It was air-cooled, used a flat design, with aluminum heads (incorporating integral intake manifolds) and crankcase, and individual iron cylinder barrels. The heads were modeled after the standard Chevrolet overhead valve design, with large valves operated by rocker arms, actuated by pushrods run off a nine lobe camshaft (exhaust lobes did double duty for two opposing cylinders) running directly on the crankcase bore without an inserted bearing, operating hydraulic valve lifters (which eliminated low temperature valve clatter otherwise seen with that much aluminum in the engine, due to its high degree of thermal expansion).


The flat horizontally opposed ("flat engine") air-cooled engine design, previously used by Volkswagen and Porsche as well as Lycoming aircraft engines, offered many advantages. Unlike inline or V designs, the horizontally opposed design made the engine inherently mechanically balanced, so that counterweights on the crankshaft were not necessary, reducing the weight greatly. Eliminating a water-cooling system further reduced the weight, and the use of aluminum for the heads and crankcase capitalized on this weight reduction; so that with the use of aluminum for the transaxle case, the entire engine/transaxle assembly weighed under 500 pounds (225 kilograms). In addition, the elimination of water-cooling eliminated several points of maintenance and possible failure, reducing them all to a single point; the fan belt. As with the Volkswagen and Porsche designs, the low weight and compact but wide packaging made the engine ideal for mounting in the rear of the car, eliminating the weight and space of a conventional driveshaft.


Two years after its 1960 debut, the Corvair engine gained another unusual attribute: it was the second production engine ever to be equipped from the factory with a turbocharger, released shortly after the Oldsmobile Jetfire V8.


Aircraft hobbyists and small volume builders, perhaps seeing the Corvair engine's similarity to Lycoming aircraft engines, very quickly began a cottage industry of modifying Corvair engines for aircraft use, which continues to this day. The Corvair engine also became a favorite for installation into modified Volkswagens and Porsches, as well as dune buggies and homemade sports and race cars.




140

The Corvair's innovative turbocharged engine; The turbo, located at top right, takes in air through the large air cleaner at top left, passes it through the sidedraft carburetor in between, and feeds pressurized fuel/air mixture into the engine through the chrome T-tube visible spanning the engine from left to right.
The Corvair's innovative turbocharged engine; The turbo, located at top right, takes in air through the large air cleaner at top left, passes it through the sidedraft carburetor in between, and feeds pressurized fuel/air mixture into the engine through the chrome T-tube visible spanning the engine from left to right.


The initial Corvair engine displaced 140 in³ (2.3 L) and produced 80 hp (60 kW). The high performance optional "Super TurboAir" version, introduced mid 1960 with a special camshaft and revised carburetors and valve springs produced 95 hp (70 kW).



145

In 1961, the engine received its first increases in size via a larger bore. The engine was now 145 in³ and the base engine was said to produce the same 80 hp (60 kW). The new high performance engine was rated at 98 hp (73 kW). In 1962 the high performance engine was rated at 102 hp (76 kW). The high compression 102 HP heads were added to the Monza models equipped with Powerglide when the standard engine was ordered, giving an 84 HP engine rating. 1962 engines returned to automatic chokes after a one year only manual choke on 1961 models.


The ultimate performance was found in the Spyder model, which became available with a turbocharged engine rated at 150 hp (112 kW). The turbocharger was mounted on the right side of the firewall behind the rear seat, fed by both exhaust manifolds; a single sidedraft carburetor mounted on the left side of the firewall fed directly into the turbocharger's intake, with a chromed pipe leading from the turbocharger's outlet to what would otherwise be the carburetor mounting pads on the intake manifolds, which were integral parts of the heads. The turbocharged heads received some valve upgrades to improve durability. Exhaust valves on turbocharged engines were made from a non-ferrous material used in jet engine turbine buckets, called 'Nimonic 80-A'. All other Corvair engines had slight upgrades in valve and valve seat materials as well for 1962.



164

The engine was stroked out (from 2.6" to 2.94") displacing 164 in (2.7 L) for 1964. Power output was boosted to 95 hp (70 kW) for the base model and 110 hp (80 kW) in the high performance normally aspirated engine, while the Turbocharged engine remained rated at 150 hp for this year. This increase in stroke was the maximum the engine could tolerate, to the point that the bottoms of the cylinder barrels had to be notched to clear the big end of the connecting rods.


For the 1965 model year, all engines had the head gasket area between the cylinder and the head widened, with a new design folded "Z" section stainless steel head gasket virtually eliminating any risk of head gasket failure. A 140 hp (104 kW) version with 4 single barrel carburetors, and a progressive linkage was introduced in 1965 as option L63 'Special High Performance Engine' and was standard equipment on the Corsa model. The carburetors consisted of a single barrel primary and a single barrel secondary on each head, connected by a progressive linkage; in addition, the heads featured a 9.25:1 compression ratio, and the cars received dual exhaust systems. Engines supplied with the automatic transmission after spring 1965 were modified with a camshaft from the 95 Horsepower base engine, and a special crankshaft gear that retarded its timing 4 degrees- the former to increase torque and smooth idle with the Powerglide transmission, the latter to restore some of the peak HP lost at higher engine speeds by the economy contoured camshaft with short timing.


1966 engines were basically carryover from the 1965 models, however Corvairs sold in California (except Turbocharged models) now featured the General Motors Air Injection Reactor System (AIR), and emissions control system consisting of an engine driven air pump that drew filtered air from the air cleaner, and injected a metered amount into the exhaust manifolds via tubing to promote complete oxidation and combustion of exhaust gasses to lower emissions. Specially calibrated carburetors and slight changes to the ignition timing and advance curves were part of the package. The AIR system had an unfortunate effect of sustantially raising exhaust gas, valve and head temperatures, particularly under heavy loads and this was a drawback on the Corvair where engine cooling could not be easily improved to cope with the higher temperatures. Nonetheless, performance and drivability were not noticably effected in most circumstances. In 1968, all Corvair (and other GM) engines got the AIR system for every market.


The 140 HP engine was officially discontinued for '67, but became optional in 1967 as COPO 9551-B, not a regular production option. Chevrolet sold 279 of these engines in the 1967 model year, 232 with manual transmissions, and 47 with Powerglide transmissions. Only six were sold with the four carburetor engine and the AIR injection system required by California emissions standards. These figures include 14 Yenko Stingers and 3 Dana Chevrolet variants of the Stinger.


Both the 140 HP engines and the Turbocharged engines had many special quality features not shared with lesser Corvairs- Moly insert top rings, stellite tips and faces on the valves, a Tufftrided (cold gas hardened) crankshaft, and Delco Moraine '400' aluminum engine bearings- the quality of the 140HP Corvair engine for materials is directly comparable to the Rolls Royce V8 of that era, item for item. It was a fabulous bargain for the $79 premium it commanded over the basic 95HP engine. Performance of the 140HP engine was better than you might expect, with a 5200 rpm peak horsepower output, it offered road performance in a Corvair comparable to contemporary Cadillac models of the day.


The turbocharged engine now developed 180 hp (134 kW). Contemporary reviews describe a similarity in power between the turbocharged and four-carburetor engines throughout the low and mid rpm range, with the turbocharged engine being superior only when it was possible to sustain boost continously. The turbocharged engines long suit was highway acceleration, flooring the accelerator at turnpike speeds produced ferocious acceleration in the upper speed ranges as the turbocharger began to boost, reaching manifold pressures approaching 15 PSI. No wastegate was used on the Corvair turbocharged engine, boost was controlled by careful balancing of exhaust restriction, mostly via the muffler, and intake restrictions from the smallish Carter YH carburetor used. Preignition and knock under boost was controlled using a novel 'pressure retard' device, essentially a modified vacuum advance device, on the specially curved distributor, as boost pressures built, ignition advance was progressively reduced to preclude detonation.

Variable geometry turbocharger

The Variable geometry turbocharger (VGT) exists in several forms, usually designed to allow the effective A/R ratio of the turbo to be altered as the conditions change. This is done as the optimum A/R at low engine speeds is very different to the optimum at high engine speeds. If too large an A/R ratio is used, the turbo will fail to create boost until a relatively high engine speed. However, if too small an A/R ratio is used, the turbo will choke the engine at high speeds, leading to large exhaust manifold pressures, high pumping losses and ultimately lower power. By altering the geometry of the turbine housing as the engine accelerates, the turbo's A/R ratio can be maintained at its optimum. Because of this, VGT turbochargers have a minimal amount of lag, have a low boost threshold and are very efficient at higher engine speeds. In many setups these turbos don't even need a wastegate. This however depends on whether the fully open position is sufficiently open to allow boost to be controlled to the desired level at all times. Some VGT implementations have been known to over-boost if a wastegate is not fitted.

The most common implementation is a set of several aerodynamically-shaped vanes in the turbine housing near the turbine inlet. As these vanes move, the area between the tips of them change, thereby leading to a variable A/R ratio. Usually, the vanes are controlled by a membrane actuator identical to the one on a wastegate, although electric servo actuated vanes are becoming more common.

The first production car to use these turbos was the limited-production 1989 Shelby CSX-VNT, equipped with a 2.2L petrol engine. The Shelby CSX-VNT utilised a turbo from Garrett, called the VNT-25 because it uses the same compressor and shaft as the more common Garrett T-25. This type of turbine is called a Variable Nozzle Turbine (VNT). Turbocharger manufacturer Aerocharger uses the term 'Variable Area Turbine Nozzle' (VATN) to describe this type of turbine nozzle. Other common terms include Variable Turbine Geometry (VTG), Variable Geometry Turbo (VGT) and Variable Vane Turbine (VVT).

The 2006 Porsche 911 Turbo has a twin turbocharged 3.6-litre flat six, and the turbos used are BorgWarner's Variable Turbine Geometry (VTGs). This is significant because although VGTs have been used on advanced turbo diesel engines for a few years and on the Shelby CSX-VNT, this is the first time the technology has been implemented on a high production petrol car (only 500 Shelby CSX-VNTs were ever produced). Exhaust temperatures in petrol cars are much higher than in diesel cars and this normally has adverse effects on the delicate, moveable vanes of the turbo. BorgWarner engineers however have managed to combat this problem with the new 911 Turbo.

Radial tire

A radial tire (more properly, a radial-ply tire) is a particular design of automotive tire (in British English, tyre). The design was originally developed by Michelin in 1946 [1] but, because of its advantages, has now become the standard design for essentially all automotive tires.

Tires are not fabricated just from rubber; they would be far too flexible and weak. Within the rubber are a series of plies of cord that act as reinforcement. All common tires (since at least the 1960s) are made of layers of rubber and cords of polyester, steel, and/or other textile materials. This network of cords that gives the tire strength and shape is called the carcass.

In the past, the fabric was built up on a flat steel drum, with the cords at an angle of about +60 and -60 degrees from the direction of travel, so they criss-crossed over each other. They were called cross ply or bias ply tires. The plies were turned up around the steel wire beads and the combined tread/sidewall applied. The green (uncured) tire was loaded over a curing bladder and shaped into the mould. This shaping process caused the cords in the tire to assume an S shape from bead to bead. The angle under the tread stretched down to about 36 degrees. This was called the Crown Angle. In the sidewall region the angle was 45 degrees and in the bead it remained at 60 degrees. The low crown angle gave rigidity to support the tread and the high sidewall angle gave comfort.

By comparison, radial tires lay all of the cord plies at 90 degrees to the direction of travel (that is, across the tire from lip to lip). This design avoids having the plies rub against each other as the tire flexes, reducing the rolling friction of the tire. This allows vehicles with radial tires to achieve better fuel economy than vehicles with bias-ply tires. It also accounts for the slightly "low on air" (bulging) look that radial tire sidewalls have, especially when compared to bias-ply tires.


Construction

As described, a radial tire would not be sufficiently strong and the surface in contact with the ground would not be sufficiently rigid. To add further strength, the entire tire is surrounded by additional belts that are oriented along the direction of travel. First made of tire cord, these belts were made of steel (hence the term "steel-belted radial") by 1948, and subsequently aramid fibers such as Kevlar.

In this way, radial tires separate the tire carcass into two separate systems:

* The radial cords in the sidewall allow it to act like a spring, giving flexibilty and ride comfort.

* The rigid steel belts reinforce the tread region, giving high mileage and performance.

Each system can then be individually optimized for best performance.

Filter (oil)

Many items requiring lubrication by petroleum products need the lubricant to be especially clean. The oil filter is a device used for this purpose, particularly in automotive and other applications for internal combustion engines.

Early automobiles did not have any way of filtering oil. For this reason, along with the low standards to which lubricating oil was generally refined in the era, very frequent oil changes, of the order of every 500 miles (800km) or 1000 miles (1600 km) were often specified for early vehicles. As automotive technology advanced, the first oil filtration devices were developed, becoming widespread by the late 1920s. Early automotive oil filters were largely of the cartridge type, generally consisting of a pleated paper element, surrounded by a metal canister perforated with many holes inside a sheet metal housing.

Cartridge-type oil filters were a considerable advance over the previous practice, of the oil going unfiltered through the engine but were still only partially effective, in that much of the oil bypassed the filter, which was located on an entirely separate oil line and, hence, went unfiltered. By the 1950s, the 'spin-on' or 'full flow' filter had become widespread. This device attaches directly to the side of the engine block, by a threaded fitting and was positioned so that all of the engine's oil capacity eventually had to pass through it during the course of normal operation. This type of filter is now used almost exclusively in modern passenger cars and, in recent years, has gained in use even in heavy-duty uses such as large truck engines and non-road going equipment such as bulldozers. Oil quality and filtering capabilities have now advanced so far that some manufacturers such as Mobil sell engine oils and filters that claim to have up to a 15,000 mile change interval. Many vehicle manufacturers recommend replacing the fitler each and every time the oil is changed. A dirty filter can quickly contaminate clean oil.

Some spin-on filters incorporate an integrated pressure relief valve. If the filter becomes completely blocked due to a lack of maintenance, this valve allows oil to bypass the blocked filter, which protects the bearings from oil starvation. The valve may also open in very cold conditions if a high viscosity oil is used.

Major brands of oil filters available in the U.S. include Fram (an Allied Signal brand), Wix, AC Delco (a General Motors brand) and Motorcraft (a Ford Motor Company brand). Some brands, such as Ford's Motorcraft, are manufactured by other companies (i.e. Purolator for Motorcraft) but are generally designed and quality tested by the brand selling them. Many of the brands manufature filters for a wide variety of makes and models of vehicles. For instance, Motorcraft sells oil filters that fit GM, Chrysler, Honda, and Toyota vehicles, in addition to Fords. The manufacturer usually provides a list of what makes and models they supply filters for.

Some have argued that there is a major difference in quality of various oil filter brands, and some studies have proven it. Generally speaking, those branded by automotive manufactuers (such as Motorcraft and AC Delco as listed above) usually meet higher standards without costing significantly more than cheaper-made (and poorer performing) brands such as Fram or Penzoil brand. Very expensive brands such as Mobil and K&N perform excellently, but cost a lot more than traditional brands.

Many major autoparts stores (such as AutoZone, which sells the Valucraft brand and NAPA, which sells NAPA and NAPA GOLD) offer their own brands of oil filters, but these are usually also made by one of the other major oil fiter makers.

Oil filters are not limited to automotive use. Power generating stations use upwards of 40,000 gallons of turbine lube oil to lubricate large bearings. Hydraulic lines are used in industry for many purposes. All of this oil needs to be filtered and the level of filtration is much more stringent than that of standard automobile filtration. In these applications many times a resin impregnated glass fiber filtration media down to even 1um is used, whereas in automobile filtration it is always cellulose which has a micron rating of 50um or more. Industrial applications do not "change their oil" frequently as changing tens of thousands of gallons of oil @ $10 a gallon quickly adds up. This is why much higher quality filters are usually used. Subsequently the cost for an industrial grade oil filter can be anywhere from $50 to $1000 (depending on size). You can not purchase an industrial grade filter and expect it to fit on your car, as these filters are sometimes 6" in diameter and upwards of 60" long. Nor would you want to, as in automobile filtration problems often result from the additives package breaking down, more so than particle contamination. Major players in industrial oil filtration are Pall, Donaldson, Parker, Kaydon, and Vickers. The industrial oil filtration market is full of retrofitted or will-fit filter elements. Every major manufacturer has a filter element that will fit in another manufacturers housing. Some manufacturers specialize in only retro-fitting other manufacturers filters elements, usually for 1/4 to 1/2 the cost.

Nissan VG engine

The VG engine family consists of V6 piston engines designed and produced by Nissan for several vehicles in the Nissan lineup. The VG series started in 1983 becoming Japan's first mass produced V6 engine. VG engines displace between 2.0 L and 3.3 L and feature an iron block and aluminum head. The early VG30 featured SOHC, 12 valve heads. A Later revision featured a slightly different block, and DOHC, 24 valve heads with Nissan's own version of variable valve timing for increased high RPM efficiency. The block is a particularly strong design with a single piece main bearing cap, and is capable of reliably supporting more than 1000hp. The production blocks and production head castings were used successfully in the Nissan IMSA cars in the 80's and 90's.

The VG series engine found its way into thousands of Nissan vehicles, starting in 1984. The VG design was retired in 2004, as all models received the VQ series engine instead.


VG20E

The VG20E is a 2 L (1998 cc) engine produced from 1984 on. It produces 126 hp.

Applications:

* Nissan Gloria/Nissan Cedric
* Nissan Leopard
* Nissan Fairlady Z


VG20ET

The VG20ET is the same as the VG20E, but with turbocharger. The VG20ET produces 170 hp.

It was used in the following vehicles:

* Nissan 200Z (Z31)
* Nissan 200ZG (Z31)
* Nissan 200ZS (Z31)


VG20DET

The VG20DET is an 2,0L engine with DOHC and a turbocharger. It produces 210 hp.

It was used in the following vehicles:

* Nissan Leopard (F31)
* Nissan Gloria/Nissan Cedric (Y31)


VG20P

The VG20P is the autogas LPG (Liquified petroleum gas) version of the VG20. It produces 99 ps @5600 rpm and 149 nm @2400 rpm. It is an OHC 12 valve engine.

It is used in the following vehicles:

1987-1991 Nissan Cedric Y31


VG30i

The VG30i is a 3 L (2960 cc) engine produced from 1986 through 1989 and featured a throttle body fuel injection system. It has a long crank snout, a cylinder head temperature sensor positioned behind the timing belt cover, and a knock sensor in the cylinder valley.

Applications:

* 1986-1989 Hardbody Truck
* 1986-1989 Nissan Pathfinder


VG30E

The 3.0 L (2960 cc) VG30E produced 153 hp and 182 ft.lbf. Bore is 3.43 in (87 mm) and stroke is 3.27 in (83 mm). In 300ZX form, it produced 160hp and 174lb-ft. 1988 saw the 300ZX gain 5 more horses for a total of 165; however, torque ratings remained the same. In 1989, the Maxima received the 160hp rating, but also used a variable intake plenum that let it make 182lb-ft@3200rpm. Strangely, the 300ZX never received the variable intake plenum.

It was used in the following vehicles:

* 1984–1989 Nissan 300ZX/Nissan Fairlady Z
* 1987–1988 Nissan 200SX SE
* 1984–1994 Nissan Maxima
* 1990–1991 Infiniti M30/Nissan Leopard
* 1990–1996 Hardbody Truck
* 1990–1995 Nissan Pathfinder/Nissan Terrano
* 1992–1999 Nissan Gloria/Nissan Cedric (179 hp)
* 1992–1995 Nissan Quest/Mercury Villager (modified to become a non-interference design)


VG30ET

The 3.0 L (2960 cc) VG30ET was available in early production with a single Garrett T3 turbocharger and a 7.8:1 compression ratio. The USDM version produced 200 hp and 227 ft.lbf. In 1988 it changed to a single Garrett T25 turbocharger and an 8.3:1 compression ratio to reduce turbo lag, and was bumped to 205 hp and 227 ft.lbf. No VG30ET was ever factory equipped with an intercooler as they featured low boost pressure for fast response.

It was used in the following vehicles:

* 1984–1989 Nissan 300ZX Turbo
* 1984–1986 Nissan Fairlady Z
* Nissan Leopard
* Nissan Gloria/Nissan Cedric


VG30DE

The 3.0 L (2960 cc) VG30DE produces 222 hp and 198 ft.lbf. Bore is 3.43 in (87 mm) and stroke is 3.27 in (83 mm).

It is used in the following vehicles:

* 1990–1996 Nissan 300ZX
* 1987–1999 Nissan Fairlady Z
* 1988 Nissan 200zx (similar chassis to the 300zx, different panels
* 1993–1998 Infiniti J30 and Nissan Leopard J. Ferie
* 1992–1995 Nissan Gloria and Cedric
* 1989–1991 Nissan Cima


VG30DET

The VG30DET is the same as the VG30DE, but with a single ceramic turbo. It produces 255 hp. It was used in the Nissan Leopard (F31)

As well as the Nissan Cima, Gloria, Cedric (y31).


VG30DETT

The 3.0 L (2960 cc) VG30DETT produces 280 hp and 283 ft.lbf when mated with a 4 speed automatic transmission. When used with a 5spd manual transmission, it was rated at 300hp and 283tq. It featured twin T25 turbochargers, twin intercoolers and variable valve timing.

It is used in the following vehicles:

* 1990–1996 Nissan 300ZX Twin Turbo
* 1990–1999 Nissan Fairlady Z Twin Turbo


VG33E

The VG33E is a 3.3 L (3275 cc) version built in Smyrna, TN. Bore is 91.5 mm and stroke is 83 mm. Output is 180 hp (134 kW) at 4800 RPM with 202 ft.lbf (274 Nm) of torque at 2800 RPM. It has a cast iron engine block and aluminum SOHC cylinder heads. It uses SFI fuel injection, has 2 valves per cylinder with roller followers and features forged steel connecting rods, a one-piece cast camshaft, and a cast aluminum intake manifold.

It is used in the following vehicles:

* 1996–1999 Nissan Pathfinder
* 2000–2004 Nissan Frontier
* 2000–2004 Nissan Xterra
* 1998–2004 Nissan Elgrand
* 1999–2002 Nissan Quest/Mercury Villager


VG33ER

The 3.3 L (3275 cc) VG33ER or VG33S is supercharged and produces 210 hp (157 kW) at 4800 RPM with 246 ft.lbf (334 Nm) of torque at 2800 RPM.

It is used in the following vehicles:

* 2001–2004 Nissan Frontier SC
* 2001–2004 Nissan Xterra SC

Mazda RX-7 Motorsport

Racing versions of the first-generation RX-7 were entered at the prestigious 24 hours of Le Mans endurance race. The first outing for the car, equipped with a 13B engine, failed by less than one second to qualify in 1979. The next year, a 12A-engine car not only qualified, it placed 21st overall. That same car did not finish in 1981, along with two more 13B cars. Those two cars were back for 1982, with one 14th place finish and another DNF. The RX-7 Le Mans effort was replaced by the 717C prototype for 1983. In 1991, Mazda became the first (and so far, only) Japanese manufacturer to win the 24 hours of Le Mans. The car was a 4-rotor prototype class car, the 787B. Le Mans outlawed rotary engines shortly after this win.

Mazda began racing RX-7s in the IMSA GTU series in 1979. That first year, RX-7s placed first and second at the 24 Hours of Daytona, and claimed the GTU series championship. The car continued winning, claiming the GTU championship seven years in a row. The RX-7 took the GTO championship ten years in a row from 1982. The RX-7 has won more IMSA races than any other car model.

The RX-7 also fared well at the Spa 24 Hours race. Three Savanna/RX-7s were entered in 1981 by Tom Walkinshaw Racing. After hours of battling with several BMW 530i and Ford Capri, the RX-7 driven by Pierre Dieudonné and Tom Walkinshaw won the event. Mazda had turned the tables on BMW, who had beaten Mazda's Familia Rotary to the podium eleven years earlier at the same event. TWR's prepared RX-7s also won the British Touring Car Championship in 1980 and 1981, driven by Win Percy.

Canadian/Australian touring car driver Allan Moffat was instrumental in bringing Mazda into the Australian touring car scene. Over a four year span beginning in 1981, Moffat took the Mazda RX-7 to victory in the 1983 Australian Touring Car Championship, as well as a trio of Bathurst 1000 podiums, in 1981 (3rd with Derek Bell), 1983 (second with Yoshima Katayama) and 1984 (third with former motorcycle champion Gregg Hansford). Australia's adoption of international Group A regulations, combined with Mazda's reluctance to homologate a Group A RX-7, ended Mazda's active participation in the touring car series at the end of the 1984 season.

The RX-7 even made an appearance in the World Rally Championship. The car finished 11th on its debut at the RAC Rally in Wales in 1981. Group B received much of the focus for the first part of the 1980s, but Mazda did manage to place third at the 1985 Acropolis Rally, and the Familia 4WD claimed the victory at Swedish Rally in both 1987 and 1989.

The RX-7 is considered as a popular choice in import drag racing, during the late nineties toward 2004 Abel Ibarra raced a spaceframe FD which averaged no less than high 6 seconds passes, until he replaced it with a spaceframe RX-8, the FD was later to shipped and sold to an Australian.

The FC and FD is considered a popular choice for drifting contests, given the long wheelbase and an average of 450bhp. Youichi Imamura won the D1 Grand Prix title in 2003 and Masao Suenaga narrowly lost his in 2005, both in FDs.

The RX-7 is a popular choice among autocross drivers,

In Japan, the RX-7 has always been a popular choice in domestic events, competing in Group 5 based Formula Silouette to its modern day incarnation, the Super GT series from when the Japan Sport Sedan series would become the GT300 category which it had been competing in. Its patience would pay off as in 2006, RE Amemiya Racing Asparadrink FD3S won the GT300 class championship.


Notes

Recently, Mazda has revived the rotary engine in the form of the RX-8. It produces approximately 232HP naturally aspirated (the FD3S produces 255hp stock with two Hitachi turbochargers), while the Japanese market version produces around 250HP.


Movies and TV

The car appeared in the Japanese anime series, Initial D, driven by the Takahashi brothers; Keisuke and Ryosuke, with Keisuke driving a yellow FD3S and Ryosuke driving a white FC3S.The FD was featured in several Need for Speed games as well as Japanese imported racing computer games. Many who played Need for Speed: Underground praised the FD for its versatile capabilities.[verification needed] The RX-7 has made an appearance in every Gran Turismo game to date, which includes many types of the different generations, including specially tuned racing versions by the various 'shops' in 'Gran Turismo mode'. The RX-7 has also been featured in every film in the 'Fast and the Furious' franchise so far.


Video Game Appearances

* Auto Modellista features all three generations of the RX-7, which can also be customized and driven.
* Driving Emotion Type-S features the FC and FD RX-7.
* D1 Grand Prix features the FC and FD models which can be customized and driven.
* Enthusia Professional Racing features all three generations of the RX-7.
* Forza Motorsport features both the FD and FC RX-7.
* Full Throttle (known as Top Speed outside Japan) was the first game to feature an FC3S in its 1987 release.
* Initial D features the FC and FD RX-7 which can be customized and driven.
* Juiced features the stock FD RX-7.
* Gran Turismo features racing and stock versions of the FC and FD RX-7.
* Gran Turismo 2 features more racing and stock versions of the RX-7.
* Gran Turismo 3: A-Spec features more racing and stock versions of the RX-7 and also offers the LM version as a prize car.
* Gran Turismo 4 features more racing and stock versions of the RX-7. Some RX-7s are also available in the Used Car Shops. The LM version again makes an appearance with notable engine sound effects.
* Gran Turismo HD will feature the Veilside RX-7.
* The Need for Speed features the 1993 FD RX-7.
* Need for Speed: Underground features an FD RX-7 that can be unlocked and then driven and modified in the game.
* Need for Speed: Underground 2 features the RX-7 with more parts available.
* Need for Speed: Most Wanted features the RX-7.
* Need for Speed: Carbon features the RX-7.
* R:Racing Evolution features the FC and FD RX-7.
* Sega GT also features the last two generations of the RX-7.
* Sega GT 2002 and its Online incarnation feature all three generations of the RX-7.
* Street Racing Syndicate features a customisable FD RX-7.
* Tokyo Xtreme Racer: Zero features all three generations of the RX-7, which can also be customized and driven
* Tokyo Xtreme Racer: 3 features all three generations of the RX-7, which can also be customized and driven
* Import Tuner Challenge Features the Mazda RX7 (1993)
* The Fast and The Furious Features the Mazda RX7 Infini and the original RX7

Mazda RX-7

The Mazda RX-7 (also called the Ẽfini RX-7) is a sports car produced by the Japanese automaker Mazda since 1978. The original RX-7 competed in the affordable sports car segment with the likes of the Nissan Fairlady Z. The styling was inspired by the Lotus Elan 2+2. It featured a unique twin-rotor Wankel rotary engine and a sporty front-midship, rear-wheel drive layout, making it well balanced and appropriate for racing. The RX-7 was a direct replacement for the RX-3 (both were sold in Japan as the Savanna) and subsequently replaced all other Mazda rotary cars with the exception of the Cosmo.

The original RX-7 was a true sports coupé design, as opposed to a sports car like the Triumph TR6 or a sedan with sporting intentions. The compact and light-weight Wankel engine, also known as a rotary engine is situated slightly behind the front axle. It was offered in America as a two-seat coupé, with four seats being optional in Japan, Australia, and other parts of the world.

The RX-7 made Car and Driver magazine's Ten Best list five times. In total, 811,634 RX-7s were produced.




First generation (SA/FB)

* Series 1 (1979–1980) is commonly referred to as the "SA22C" from the first alphanumerics of the vehicle identification number- although RX-7 tech site Rotorhead.ca points out that the chassis code used by Mazda was 'P642'. This series of RX-7 had exposed steel bumpers and a high-mounted license plate located in an indented part of the rear of the car, famously criticized by Werner Buhrer of Road & Track magazine as a "Baroque depression."

* Series 2 (1981–1983) had smoothly integrated plastic-covered bumpers, wide black rubber body side moldings, wraparound taillights and updated engine control components. The GSL package provided optional 4-wheel disc brakes and clutch-type rear limited slip differential (LSD). Known as the "FB" in North America after the US Department of Transportation mandated 17 digit Vehicle Identification Number changeover. Elsewhere in the world, the 1981-1985 RX-7 is technically still an 'SA22C' among enthusiasts.

* Series 3 (1984–1985) featured an updated lower front fascia and different instrument cluster (the S3 RX-7 is the only rotary-engined car to not have a centrally mounted tachometer). GSL package was continued into this series, but Mazda introduced the GSL-SE sub-model. The GSL-SE had a fuel injected 1.3 L 13B RE-EGI engine producing 135 hp (101 kW) and 135 lb-ft. GSL-SEs had much the same options as the GSL (clutch-type rear LSD and rear disc brakes), but the brake rotors were larger, allowing Mazda to use the more common lug nuts (versus bolts), and a new bolt pattern of 4x114.3 (4x4.5"). Also, they had upgraded suspension with stiffer springs and shocks, and a new, heavy duty oil cooler.

The 1984 RX-7 S has an estimated 29 highway miles per gallon (12.33 kilometres per litre)/19 estimated city miles per gallon (8.08 k/l). According to Mazda, its rotary engine, licensed by NSU-Wankel allowed the RX-7 S to accelerate from 0 to 50 (80kph) in 6.3 seconds. Kelley Blue Book, in its January-February 1984 issue, noted that a 1981 RX-7 S retained 93.4% of its original sticker price.

The handling and acceleration of the car were noted to be of a high caliber for its day. This generation RX-7 had "live axle" 4-link rear suspension with Watt's linkage, a 50/50 weight ratio, and weighed under 2600 lb (1180 kg). It was the lightest generation of RX-7 ever produced. 12A-powered models accelerated from 0–60 mph in 9.2 s, and turned 0.779 lateral Gs on a skidpad. The 12A engine produced 100 hp (75 kW) at 6000 rpm, allowing the car to reach speeds of over 120 mph (190 km/h). Because of the smoothness inherent in the Wankel rotary engine, little vibration or harshness was experienced at high rpm, so a buzzer was fitted to the tachometer to warn the driver when the 7000 rpm redline was approaching.

Options and models varied from country to country. The gauge layout and interior styling in the Series 3 was only changed for North American versions. Additionally, North America was the only market to have offered the first generation RX-7 with the fuel injected 13B. A turbocharged (but non-intercooled) 12A engine was available for the top-end model of Series 3 in Japan.

Sales were strong, with a total of 474,565 first generation cars produced; 377,878 were sold in the United States alone. In 2004, Sports Car International named this car #7 on its list of Top Sports Cars of the 1970s. In 1983, the RX-7 would appear on Car and Driver magazine's Ten Best list for the first time.



Second generation (FC)


* Series 4 (1986–1988) was available with a naturally aspirated, fuel-injected 13B-VDEI producing 146 hp (108 kW). An optional turbocharged model, known as the Turbo II, had 182 hp (141 kW).

* Series 5 (1989–1992) featured updated styling and better engine management, as well as lighter rotors and a higher compression ratio, 9.7:1 for the naturally aspirated model, and 9.0:1 for the turbo model. The Turbo II monicker was dropped, and the turbocharged model was simply dubbed Turbo. The naturally aspirated Series 5 FC made 160 hp (119 kW), while the Series 5 Turbo made 200 hp (147 kW).

The second generation RX-7 ("FC", VIN begins JM1FC3 or JMZFC1), still known as the "Savanna RX-7" in Japan, featured a complete restyling reminiscent of the Porsche 928. Mazda's stylists, lead by Chief Project Engineer Akio Uchiyama, actually focused more on the Porsche 944 for their inspiration in designing the FC because the new car was being styled primarily for the American market where the majority of first generation RX-7's had been sold. This strategy was chosen after Uchiyama and others on the design team spent time in the United States studying owners of earlier RX-7's and other sports cars popular in the American market. The Porsche 944 was selling particularly well at the time and provided clues as to what sports car enthusiasts might find compelling in future RX-7 styling and equipment. While the SA22/FB was a purer sports car, the FC tended toward the softer sport-tourer trends of its day. Handling was much improved, with less of the oversteer tendencies of the FB. Steering was more precise, with rack and pinion steering replacing the old recirculating ball steering of the FB. Disc brakes also became standard, with some models (S4: GXL, GTU, Turbo II, Convertible; S5: GTUs, Turbo, Convertible) offering four-piston front brakes. The revised independent rear suspension incorporated special toe control hubs which were capable of introducing a limited degree of passive rear steering under cornering loads. The rear seats were optional in some models of the FC RX-7, but are not commonly found.

Though about 80 lb heavier and more isolated than its predecessor, the FC continued to win accolades from the press. The FC RX-7 was Motor Trend's Import Car of the Year for 1986, and the Turbo II was on Car and Driver magazine's Ten Best list for a second time in 1987.

In 1988, a convertible version started production in atmospheric and turbocharged form, proving an instant success. This sleek, clean lined model featured a cabriolet design and was introduced to the American market in splashy television advertisements featuring Hollywood actor James Garner. Several leading car magazines at the time also selected the convertible as the best ragtop available on the market, and it was the star of auto shows around the globe. The convertible's well orchestrated introduction caused a notable public sensation and heavy demand for these vehicles. Dealers took full advantage of the situation, charging up to $5,000 above Mazda's suggested retail selling price with buyers happy to pay the premium. It is believed Mazda exported approximately five thousand convertibles to the United States in 1988 and fewer in each of the next three model years, although it is difficult to confirm these figures, as Mazda USA did not keep RX-7 import records by model type. Despite production ceasing in October 1991, Mazda built a limited run of 500 convertibles for 1992 as "specials" for the domestic market only. In Japan, the United Kingdom, and other regions outside the US, a turbocharged version of the convertible was available. Being former "dream cars", it now appears a nascent collectors market is developing for these classic, semi-exotic sports cars.

In the Japanese market, only the turbo engine was available; the atmospheric version was allowed only as an export. This can be attributed to insurance companies penalising turbo cars (thus restricting potential sales). This emphasis on containing horsepower and placating insurance companies to make RX-7's more affordable seems ironic in retrospect. Shortly after the discontinuance of the second generation RX-7's in 1991, an outright horsepower "arms race" broke out between sports car manufacturers, with higher and higher levels of horsepower required to meet buyer demands.

Overall, the second generation was the most successful for Mazda sales wise, with 86,000 units sold in the US alone in 1986, its first model year. The FC model is believed to have achieved its peak in sales in 1988..



Third generation (FD)

* Series 6 (1992–1995) was exported throughout the world and had the highest sales. In Japan, Mazda sold the RX-7 through its Efini brand as the Efini RX-7. Only the 1993–1995 model years were sold in the U.S. and Canada.

* Series 7 (1996–1998) included minor changes to the car. Updates included a simplified vacuum routing manifold and a 16-bit ECU allowing for increased boost which netted an extra 10 hp. In Japan, the Series 7 RX-7 was marketed under the Mazda brand name. The Series 7 was also sold in Australia, New Zealand and the U.K. Series 7 RX-7s were produced only in right-hand-drive configuration.

* Series 8 (January 1999– August 2002) was the final series, and was only available in the Japanese market. More efficient turbochargers were installed, while improved intercooling and radiator cooling was made possible by a revised frontal area. The seats, steering wheel, and front and rear lights were all changed. The rear wing was modified and gained adjustability. The top-of-the-line "Type RS" came equipped with a Bilstein suspension and 17" wheels as standard equipment, and reduced weight to 1280 kg. Power was officially claimed as 280 ps (276 hp, 208 kW) (with 330 N·m (243 ft·lbf) of torque) as per the maximum Japanese limit, though realistic power was more likely 220–230 kW (290–308 hp). The Type RZ version included all the features of the Type RS, but at a lighter weight (at 1270 kg). It also featured custom gun-metal colored BBS wheels and a custom red racing themed interior. Further upgrades included a new 16-bit ECU and ABS system upgrades. The improved ABS system worked by braking differently on each wheel, allowing the car better turning during braking. The effective result made for safer driving for the average buyer. Easily the most collectible of all the RX-7s was the last 1,500 run-out specials. Dubbed the "Spirit R", they combined all the "extra" features Mazda had used on previous limited-run specials and all sold within days of being announced. They still command amazing prices on the Japanese used car scene years later.

-There are three kinds of "Spirit R"s: the "Spirit A", "Spirit B", and "Spirit C". The "Spirit A", which accounts for 1,000 of the 1,500 "Spirit" models produced, has a 5-speed manual transmission, and is said to have the best performance of the three models. The "Spirit B" is a four-seater, and sports a 5-speed manual transmission. "The Spirit C" is also a four-seater, but has a 4-speed automatic transmission.

There is also a "Touring Model" which includes a sun roof, and Bose stereo system. Compared to the R1 and R2 which both don't have a moon roof, and they have an extra front oil cooler in the front bumper, and other race modification equipment

The third and final generation of the RX-7, FD (with FD3S for the JDM and JM1FD for the USA VIN), was an outright, no-compromise sports car by Japanese standards. It featured an aerodynamic, futuristic-looking body design (a testament to its near 11-year lifespan). The 13B-REW was the first-ever mass-produced sequential twin-turbocharger system to export from Japan, boosting power to 255 hp (190 kW) in 1993 and finally 280 ps (276 hp, 208 kW, the Japanese manufacturers' gentlemen's agreement on engine power) by the time production ended in Japan in 2002.

The FD RX-7 was Motor Trend's Import\Domestic Car of the Year. When Playboy magazine first reviewed the FD RX-7 in 1993, they tested it in the same issue as the [then] new Dodge Viper. In that issue, Playboy declared the RX-7 to be the better of the two cars. It went on to win Playboy's Car of the Year for 1993. The FD RX-7 also made Car and Driver magazine's Ten Best list for 1993 through 1995.

The sequential twin turbocharged system was a very complex piece of engineering, developed with the aid of Hitachi and previously used on the domestic Cosmo series (JC Cosmo=90–95). The system was comprised of two small turbochargers, one to provide torque at low RPM. The 2nd unit was on standby until the upper half of the rpm range during full throttle acceleration. The first turbocharger provided 10 psi of boost from 1800 rpm, and the 2nd turbocharger was activated at 4000 rpm and also provided 10 psi (70 kPa). The changeover process was incredibly smooth, and provided linear acceleration and a very wide torque curve throughout the entire rev range.

Handling in the FD was regarded as world-class, and it is still regarded as being one of the finest handling and best balanced cars of all time. The continued use of the front-midship engine and drivetrain layout, combined with an 50:50 front-rear weight distribution ratio and low center of gravity made the FD a very competent car at the limits.

In North America, three models were offered; the "base", the touring, and the R models. The touring FD had a sunroof, leather seats, and a complex Bose Acoustic Wave system. The R (R1 in 1993 and R2 in 1994–95) models featured stiffer suspensions, an aerodynamics package, suede seats, and Z-rated tires.

Australia had a special high performance version of the RX-7 in 1995, dubbed the RX-7 SP. This model was developed as a homologated road-going version of the race car used in the 12hr endurance race held at Bathurst, New South Wales, beginning in 1991. An initial run of 25 were made, and later an extra 10 were built by Mazda due to demand. The RX-7 SP produced 204 kW (274 hp) and 357 N·m (263 ft·lbf) of torque, compared to 176 kW (236 hp) and 294 N·m (217 ft·lbf) on the standard version. Other changes included a race-inspired nose cone, race-proven rear wing, a 120 L fuel tank (as opposed to the 76 L tank in the standard car), a 4.3:1-ratio rear differential, 17 in diameter wheels, larger brake rotors and calipers. An improved intercooler, exhaust, and modified ECU were also included. Weight was reduced significantly with the aid of carbon fibre; a lightweight bonnet and seats were used to reduce weight to just 1218 kg (from 1310 kg). It was a serious road going race car that matched their rival Porsche 968CSRS for the final year Mazda officially entered. The formula paid off when the RX-7SP won the title, giving Mazda the winning trophy for a fourth straight year. A later special version, the Bathurst R, was released in 2001.

A popular modification to the 3rd Gen RX-7 is the substitution of a 20B (2.0 litre) 3-rotor engine taken from the Eunos Cosmo in place of the stock 13B (1.3 litre) 2-rotor engine. Many aftermarket performance houses sell conversion kits with the 20B engine, such as Stillen and Pettit Racing. Such 3-rotor configurations typically produce 550hp and a top speed of well over 200 MPH. While critics claim that any 13B 2-rotor RX-7 can be highly tuned to achieve this level of performance, the difference is in daily drivability and reliability that makes the 20B conversion superior to the stock 13B motor.

Front mounted intercooler

Front mounted intercooler, an IC mount position, which involves mounting the intercooler at the front of the engine, usually in the bumper. Often found in high performance cars, although many manufacturers and racing teams use TMICs.

FMICs generally require open bumpers, and front spoilers, which will force air into the bumper and provide downforce 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. Secondly, FMICs, by virtue of their siting 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. Thirdly, 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 (acceptable for a personally modified car, but a major detriment to a stock car). One of the very few manufacturers to offer an FMIC setup in their factory street cars is Mitsubishi, in the Lancer Evolution series.

Top mounted intercooler

A top mounted intercooler (TMIC) is an automotive intercooler mounted within the engine bay, above the engine. Because of restricted airflow to this location, a hood scoop is virtually a necessity for a TMIC.






TMIC is circled in red


Advantages

* The TMIC may be placed close to the turbocharger and/or supercharger compressor and to the engine's intake. As a result, the intake tubing can be kept short. The longer the path from the intercooler to the engine, the more air must be pressurised within the hoses when a change in pressure is demanded - and the greater the lag imposed. When used in combination with quick-spooling turbochargers, such as ball bearing turbochargers, the result is a more responsive engine.

* Unlike front-mounted intercoolers, TMICs do not block any airflow to the radiator and/or oil cooler, allowing better engine cooling.


Disadvantages

* Heat from the engine may be conducted through to the intercooler, usually while trying to escape through an open hood vent. For this reason hot, cramped or poorly ducted engine bays (commonly the case with rotary engines) negatively affect the performance of TMICs.

* TMICs tend to be less efficient than similarly sized front mount intercoolers, due to the smaller amount of cold air flow through the hood scoop compared to the front grille area in most car designs.


Applications

TMICs are used in many street cars, such as all current intercooled Subarus, the MINI Cooper'S and also in older cars such as the Mazda RX-7 (86-91 model).

A properly designed top mount intercooler's advantage in responsiveness is preferred over more lagging front mount intercoolers in situations where responsiveness is more important than total power - notably in rallying, drifting, autocross and touge.


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 utilised 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.

Torque converter

A torque converter is modified form of a hydrodynamic fluid coupling, and like the fluid coupling, is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load. As with the fluid coupling, the torque converter takes the place of a mechanical clutch. Unlike a fluid coupling, however, a torque converter is able to multiply torque when there is a substantial difference between input and output rotational speed, thus providing the equivalent of a reduction gear. The most widespread usage of torque converters is in automobile, bus and light truck automatic transmissions. Torque converters are also found in marine propulsion systems and industrial applications.



Function

Torque Converter Elements

A torque converter is a type of hydrodynamic drive whose function is very similar to that of a fluid coupling. The principal difference is that whereas a fluid coupling is a two element drive that is incapable of multiplying torque, a torque converter has at least one extra element—the stator—which alters the drive's characteristics during periods of high slippage, producing an increase in output torque. It is suggested to the reader that he or she become familiar with the principles of hydrodynamic drives before continuing by reading the fluid coupling article.

In a torque converter there are at least three rotating elements: the pump, which is mechanically driven by the prime mover; the turbine, which drives the load; and the stator, which is interposed between the pump and turbine so that it can alter oil flow returning from the turbine to the pump. The classic torque converter design dictates that the stator be prevented from rotating under any condition, hence the term stator. In practice, however, the stator is mounted on an overrunning clutch, which prevents the stator from counter-rotating the prime mover but allows for forward rotation.

Modifications to the basic three element design have been periodically found, especially in applications where higher than normal torque mutiplication is required. Most commonly, these have taken the form of multiple turbines and stators, each set being designed to produce differing amounts of torque multiplication. For example, the Buick Dynaflow automatic transmission was a non-shifting design and, under normal conditions, relied solely upon the converter to multiply torque. The Dynaflow used a five element converter to produce the wide range of torque multiplication needed to propel a heavy vehicle.

Although not strictly a part of classic torque converter design, many automotive converters include a lock-up clutch to improve cruising power transmission efficiency. The application of the clutch locks the turbine to the pump, causing all power transmission to be mechanical, thus eliminating losses associated with fluid drive.


Operational Phases

For the purposes of explanation, a torque converter can be considered to have three stages of operation:

* Stall. The prime mover is applying power to the pump but the turbine cannot rotate. For example, in an automobile, this stage of operation would occur when the driver has placed the transmission in gear but is preventing the vehicle from moving by continuing to apply the brakes. At stall, the torque converter can produce maximum torque multiplication if sufficient input power is applied (the resulting multiplication is called the stall ratio). The stall phase actually lasts for a brief period when the load (e.g., vehicle) initially starts to move, as there will be a very large difference between pump and turbine speed.

* Acceleration. The load is accelerating but there still is a relatively large difference between pump and turbine speed. Under this condition, the converter will produce torque multiplication that is less than what could be achieved under stall conditions. The amount of multiplication will depend upon the actual difference between pump and turbine speed, as well as various other design factors.

* Coupling. The turbine has reached approximately 90 percent of the speed of the pump. Torque multiplication has ceased and the torque converter is behaving in a manner similar to a fluid coupling. In modern automotive applications, it is usually at this stage of operation where the lock-up clutch is applied, a procedure that tends to improve fuel efficiency.

The key to the torque converter's ability to multiply torque lies in the stator. In the classic fluid coupling design, periods of high slippage cause the fluid flow returning from the turbine to the pump to oppose the direction of pump rotation, leading to a significant loss of efficiency and the generation of considerable waste heat. Under the same condition in a torque converter, the returning fluid will be redirected by the stator so that it aids the rotation of the pump, instead of impeding it. The result is that much of the energy in the returning fluid is recovered and added to the energy being applied by the pump itself. This action causes a substantial increase in the mass of fluid being directed to the turbine, producing an increase in output torque. Since the returning fluid is initially traveling in a direction opposite to pump rotation, the stator will likewise attempt to counter-rotate as it forces the fluid to change direction, an effect that is resisted by the one-way stator clutch.

Unlike the radially straight blades used in a fluid coupling, a torque converter's turbine and stator use angled and curved blades. The blade shape of the stator is what alters the path of the fluid, forcing it to coincide with the pump rotation. The matching curve of the turbine blades helps to correctly direct the returning fluid to the stator so the latter can do its job. The shape of the blades represents a bit of a black art in converter design, as minor variations can result in significant changes to the converter's performance.

During the stall and acceleration phases, in which torque multiplication occurs, the stator remains stationary due to the action of its one-way clutch. However, as the torque converter approaches the coupling phase, the energy and volume of the fluid returning from the turbine will gradually decrease, causing pressure on the stator likewise decrease. Once in the coupling phase, the returning fluid will reverse direction and now rotate in the direction of the pump and turbine, an effect which will attempt to forward-rotate the stator. At this point, the stator clutch will release and the pump, turbine and stator will all (more or less) turn as a unit.

Unavoidably, some of the fluid's kinetic energy will be lost due to friction and turbulence, causing the converter to waste heat (dissipated in many applications by water cooling). This effect, often referred to as pumping loss, will be most pronounced at or near stall conditions. In modern designs, the blade geometry minimizes oil velocity at low pump speeds, which allows the turbine to be stalled with the engine at idle speed for long periods with little danger of overheating.


Efficiency and Torque Multiplication

A torque converter cannot achieve 100 percent coupling efficiency. The Twin Turbine Dynaflow torque converter has an efficiency curve that resembles an inverted letter J: zero efficiency at stall, maximum efficiency at approximately 50 percent coupling, and very low efficiency at maximum coupling while the classic three element torque converter has an asymptotical efficiency curve that resembles an inverted U. The loss of efficiency as the converter enters the coupling phase is a result of the turbulence and fluid flow interference generated by the stator, and as mentioned above, is commonly overcome by mounting the stator on a one-way clutch.

Even with the benefit of the one-way stator clutch, a converter cannot achieve the same level of efficiency in the coupling phase as an equivalently sized fluid coupling. Some loss is due to the presence of the stator (even though rotating as part of the assembly), as it always generates some power-absorbing turbulence. Most of the loss, however, is caused by the curved and angled turbine blades, which do not absorb kinetic energy from the fluid mass as well as radially straight blades. Since the turbine blade geometry is a crucial factor in the converter's ability to multiply torque, trade-offs between torque multiplication and coupling efficiency are inevitable. In automotive applications, where steady improvements in fuel economy have been mandated by market forces and government edict, the nearly universal use of a lock-up clutch has helped to eliminate the converter from the efficiency equation during cruising operation.

The maximum amount of torque multiplication produced by a converter is highly dependent on the size and geometry of the turbine and stator blades, and is generated only when the converter is at or near the stall phase of operation. Typical stall torque multiplication ratios range from 1.8:1 to 2.5:1 for most automotive applications (although multi-element designs as used in the Buick Dynaflow and Chevrolet Turboglide could produce more). Specialized converters design for industrial or heavy marine power transmission systems are capable of as much as 5.0:1 multiplication. Generally speaking, there is a trade-off between maximum torque multiplication and efficiency—high stall ratio converters tend to be relatively inefficient below the coupling speed, whereas low stall ratio converters tend to provide less possible torque multiplication.

While torque multiplication increases the torque delivered to the turbine output shaft, it also increases the slippage within the converter, raising the temperature of the fluid and reducing overall efficiency. For this reason, the characteristics of the torque converter must be carefully matched to the torque curve of the power source and the intended application. Changing the blade geometry of the stator and/or turbine will change the torque-stall characteristics, as well as the overall efficiency of the unit. For example, drag racing automatic transmissions often use converters modified to produce high stall speeds to improve off-the-line torque, and to get into the power band of the engine more quickly. Highway vehicles generally use lower stall torque converters to limit heat production, and provide a more firm feeling to the vehicle's characteristics.

A design feature once found in some General Motors automatic transmissions was the variable-pitch stator, in which the blades' angle of attack could be varied as much as 75 degrees in response to changes in engine speed and load. The effect of this was to vary the amount of torque multiplication produce by the converter. At the normal angle of attack, the stator caused the converter to produce a moderate amount of multiplication but with a higher level of efficiency. If the driver abruptly opened the throttle, a valve would switch the stator pitch to a different angle of attack, increasing torque multiplication at the expense of efficiency.

Some torque converters use multiple stators and/or multiple turbines to provide a wider range of torque multiplication. Such multiple-element converters are more common in industrial environments than in automotive transmissions, but automotive applications such as Buick's Triple Turbine Dynaflow and Chevrolet's Turboglide also existed. The Buick Dynaflow utilized the torque-multiplying characteristics of the its planetary gearset in conjunction with the torque converter for low gear and bypassed the first turbine, using only the second turbine as vehicle speed increased. The unavoidable trade-off with this arrangement was poor efficiency and eventually these transmission were discontinued in favor of the more efficient three speed units with a conventional torque converter.

Lock-up Torque Converters

As described above, pumping losses within the torque converter reduce efficiency and generate waste heat. In modern automotive applications, this problem is commonly avoided by use of a lock-up clutch that physically links the pump and turbine, effectively changing the converter into a purely mechanical coupling. The result is no slippage, and therefore virtually no power loss.

The first automotive application of the lock-up principle was Packard's Ultramatic transmission, introduced in 1949, which locked up the converter at cruising speeds, unlocking when the throttle was floored for quick acceleration or as the vehicle slowed down. This feature was also present in some Borg-Warner automatics produced during the 1950's. It fell out of favor in subsequent years due the extra complexity and cost it added to the transmission. However, in the late 1970's lock-up clutches started to reappear in response to demands for improved fuel economy. They are now nearly universal in automotive applications.


Capacity and Failure Modes

As with a fluid coupling, the theoretical torque capacity of a converter is proportional to r(N^2)(D^5), where r is the mass density of the fluid, N is the impeller speed, and D is the diameter. In practice, the maximum torque capacity is limited by the mechanical characteristics of the materials used in the converter's components, as well as the ability of the converter to dissipate heat (often through water cooling). As an aid to strength, reliability and economy of production, most automotive converter housings are of welded construction. Industrial units are usually assembled with bolted housings, a design feature that eases the process of inspection and repair, but adds to the cost of producing the converter.

In high performance, racing and heavy duty commercial converters, the pump and turbine may be further strengthened by a process called furnace brazing, in which molten brass is forced into seams and joints to produce a stronger bond between the blades, hubs and annular ring(s). Because the furnace brazing process creates a small radius at the point where a blade meets with a hub or annular ring, a theoretical decrease in turbulence will occur, resulting in a corresponding increase in efficiency.

Overloading a converter can result in several failure modes, some of them potentially dangerous in nature:

* Overheating: Continuous high levels of slippage may overwhelm the converter's ability to dissipate heat, resulting in damage to the elastomer seals that retain fluid inside the converter. This will cause the unit to leak and eventually stop functioning due to lack of fluid.

* Stator Clutch Seizure: The inner and outer elements of the one-way stator clutch become permanently locked together, thus preventing the stator from rotating during the coupling phase. Most often, seizure is precipitated by severe loading and subsequent distortion of the clutch components. Eventually, galling of the mating parts occurs, which triggers seizure. A converter with a seized stator clutch will exhibit very poor efficiency during the coupling phase, and in a motor vehicle, fuel consumption will drastically increase. Converter overheating under such conditions will usually occur if continued operation is attempted.

* Stator Clutch Breakage: A very abrupt application of power can cause shock loading to the stator clutch, resulting in breakage. When this occurs, the stator will freely counter-rotate the pump and almost no power transmission will take place. In an automobile, the effect is similar to a severe case of transmission slippage and the vehicle is all but incapable of moving under its own power.

* Blade Deformation and Fragmentation: Due to abrupt loading or excessive heating of the converter, the pump and/or turbine blades may be deformed, separated from their hubs and/or annular rings, or may break up into fragments. At the least, such a failure will result in a significant loss of efficiency, producing symptoms similar (although less pronounced) to those accompanying stator clutch failure. In extreme cases, catastrophic destruction of the converter will occur.

* Ballooning: Prolonged operation under excessive loading, very abrupt application of load, or operating a torque converter at very high RPM may cause the shape of the converter's housing to be physically distorted due to internal pressure and/or the stress imposed by centrifugal force. Under extreme conditions, ballooning will cause the converter housing to rupture, resulting in the violent dispersal of hot oil and metal fragments over a wide area.

Vehicle tracking system

Vehicle Tracking Systems are electronic devices installed in vehicles to enable vehicle owners or third parties to track the location of a vehicle. Most modern vehicle tracking systems now use GPS modules to allow for easy and accurate location of the vehicle. Many systems also combine a communications component such as cellular or satellite transmitters to communicate the vehicle’s location to a remote user. Vehicle information can be viewed on electronic maps via the Internet or specialized software.

Current vehicle tracking systems have their roots in the shipping industry. Corporations with large fleets of vehicles required some sort of system to determine where each vehicle was at any given time. Vehicle tracking systems can now also be found in consumers vehicles as a theft prevention and retrieval device. Police can simply follow the signal emitted by the tracking system and locate the stolen vehicle.

Many vehicle tracking systems are now using GPS or a form of Automatic Vehicle Location (AVL) to allow for easy location of the vehicle. The GPS satellite system was built and is maintained by government and is available at no cost to civilians. This makes this technology very inexpensive. Other AVL systems do not require the antenna to be in direct line of sight with the sky. Terrestrial based systems such as Loran and LoJack tracking units use radio frequency (RF) transmitters which will transmit through walls, garages, or buildings. Many police cruisers around the world have a form of AVL tracking as standard equipment in their vehicles.

Some vehicle tracking systems incur a cost to the user in the form of monthly fees. Companies such as StreetEagle, and Track Star bundle mapping software, with hardware, installation and tracking into monthly subscriptions. Other companies such as the LoJack units are paid for upon installation and will continue to work for the life of the vehicle. The decision to adopt an active technology based on RF (e.g. Loran), satellite or public carrier (e.g. CDMA) is driven by the quantity of information, the frequency of updates, and the physical environment of the device. For example a fleet manager may want 5 minute updates, telling whether a vehicle is on or off, or may want 30 second updates tracking engine vitals, brake status, container status, vehicle speed and direction and so on.



Active versus passive tracking

Several types of Vehicle Tracking devices exist. Typically they are classified as Passive and Active. Passive devices store GPS location, speed, heading and sometime a trigger event such as key on/off, door open/closed. Once the vehicle returns to a pre-determined point, the device is removed and the data downloaded to a computer for evaluation. Active devices also collect the same information but usually transmit the data in real-time via cellular or satellite networks to a computer or data center for evaluation.

Some taxi services are using vehicle tracking systems for better serving their customers. By using Vehicle Tracking Systems, their operators can see all their empty taxis, so they can choose the closer one to pickup the order from their customer.


Common uses

Vehicle Tracking Systems are commonly used by fleet operators for fleet management functions such as routing, dispatch, on-board information and security. Other applications include monitoring driving behavior, such as an employer of an employee, or a parent with a teen driver.

Vehicle tracking systems are also popular in consumer vehicles as a theft prevention and retrieval device. Police can simply follow the signal emitted by the tracking system and locate the stolen vehicle. When used as a security system, a Vehicle Tracking System may serve as either an addition to or replacement for a traditional Car alarm. The existence of vehicle tracking device then can used to reduce the insurance cost, because the lost risk of the vehicle drops significantly.

Vehicle Tracking Systems are an integrated part of the “layered approach” to vehicle protection, recommended by the National Insurance Crime Bureau (NICB) to prevent motor vehicle theft. This approach recommends four layers of security based on the risk factors pertaining to a specific vehicle. Vehicle Tracking Systems are one such layer, and are described by the NICB as “very effective” in helping police recover stolen vehicles.

Some Vehicle Tracking Systems integrate several security systems, for example by sending an automatic alert to a phone or email if an alarm is triggered or the vehicle is moved without authorization.


Major markets

Vehicle Tracking can be used in the following scenarios;

Stolen Vehicle Recovery: Both consumer and commercial vehicles can be outfitted with RF or GPS units to allow police to do tracking and recovery. In the case of LoJack, the police can activate the tracking unit in the vehicle directly and follow tracking signals.

Fleet Management: When managing a fleet of vehicles, knowing the real-time location of all drivers allows management to meet customer needs more efficiently. Whether it is delivery, service or other multi-vehicle enterprises, drivers now only need a mobile phone with telephony or Internet connection to be inexpensively tracked by and dispatched efficiently. Asset Tracking: Companies needing to track valuable assets for insurance or other monitoring purposes can now plot the real-time asset location on a map and closely monitor movement and operating status.

Field Service Management: Companies with a field service workforce for services such as repair or maintenance, must be able to plan field workers’ time, schedule subsequent customer visits and be able to operate these departments efficiently. Vehicle tracking allows companies to quickly locate a field engineer and dispatch the closest one to meet a new customer request or provide site arrival information.

Field Sales: Mobile sales professionals can access real-time locations. For example, in unfamiliar areas, they can locate themselves as well as customers and prospects, get driving directions and add nearby last-minute appointments to itineraries. Benefits include increased productivity, reduced driving time and increased time spent with customers and prospects.

Trailer Tracking: Haulage and Logistics companies often operate lorries with detachable load carrying units. The part of the vehicle that drives the load is know as the cab and the load carrying unit is known as the trailer. There are different types of trailer used for different applications, e.g. flat bed, refrigerated, curtain sider, box container.

Suzuki DL650 VStrom

Following their introduction of the DL1000 in 2002 (verify), Suzuki introduced the DL650 V-Strom in 2004 as a dual-purpose motorcycle, emphasizing the bike's on-road rather than off-road capability.

For the purpose of further distinguishing the two bikes, members of two large enthusiast groups (Vstrom.info and Stromtrooper.com) often refer to the DL1000 as the "Vee" or "Vee-Strom" and the DL650 as the "Wee" or Wee-strom."

With a 6-speed transmission mated to the fuel-injected and slightly re-retuned 650cc V-twin engine from Suzuki's own SV650 sport bike, the DL650 provides a combination of light weight, energetic acceleration and agile handling. These qualities -- along with the bike's price, fuel economy, large fuel capacity and upright riding position -- combine to make the V-Strom 650 adaptable to a wide range of applications from commuting to off-road and touring duties. For 2007, Suzuki offers ABS for the DL650, reinforcing the bike's capability.


Suzuki's DL650 has found a following across Europe, Oceania and the America's, including new and re-entry riders, riders down-sizing from unwieldy heavier bikes and adventure-touring riders who recognize despite the Wee-Strom's prosaic styling and humble specification a bike of broad capability.

Twice consecutively, the DL650 has earned the title Alpenkoenig, winning the German magazine Motorrad's grueling trans-alp multi-bike test in 2005 and 2006.

In a September 2006 article, Cycle World magazine declared the DL650 "may just be the most shockingly competent machine in the world today."

Dry gas

Dry gas is an ethanol-based additive used in automobiles to prevent any water in the fuel from freezing, or to restore combustive power to gasoline spoiled by water. It is a liquid that is added in to the fuel tank, that absorbs the water and keeps it in solution. (Some brands contain methanol and some contain isopropyl alcohol.)

Some states require a 10-15% ethanol solution be sold at refueling stations. Most current gasoline-powered automobiles can safely run up to a 15% ethanol solution without any modification. However, at 20% or above older vehicles may require replacing the fuel lines to prevent degradation and rupture, and the electric fuel pump may need modification to prevent ethanol "dry rot". There is no point in adding dry gas to fuel that already contains a significant percentage of ethanol.

Dry gas also describes natural gas that is always in the gaseous state, because it produces little condensable hydrocarbons.

Distributor

The distributor in the ignition system of an internal combustion engine is a device which routes the high voltage in the correct firing order to the spark plugs.

It consists of a rotating arm or rotor inside the distributor cap, on top of the distributor shaft, but insulated from it and the body of the vehicle ("earth"). The metal part of the rotor contacts the central high voltage cable from the coil via a spring loaded carbon brush. The metal part of the rotor arm passes close to (but does not touch) the output contacts which connect via high tension cables to the spark plug of each cylinder. As the rotor spins within the distributor, electrical current is able to jump the small gaps created between the rotor arm and the contacts due to the high voltage created by the ignition coil.

The distributor shaft has a cam that operates the contact breaker. Opening the points causes a high induction voltage in the system's ignition coil.

The distributor also houses the centrifugal advance unit: a set of hinged weights attached to the distributor shaft, that cause the breaker points mounting plate to slightly rotate and advance the spark timing with higher engine rpm. In addition, the distributor has a vacuum advance unit that advances the timing even further as a function of the vacuum in the inlet manifold. Usually there is also a capacitor attached to the distributor. The capacitor is connected parallel to the breaker points, to suppress sparking and prevent wear of the points.

Around the 1970s the primary breaker points were largely replaced with Hall effect sensors. As this is a non-contacting device and the primary circuit is controlled by solid state electronics, a great amount of maintenance in point adjustment and replacement was eliminated. This also eliminates any problem with breaker follower or cam wear, and by eliminating a side load extends distributor shaft bearing life. The remaining secondary (high voltage) circuit was as described above, using a single coil and a rotary distributor.


Distributor caps

These are used in automobile engine to cover the distributor and its internal rotor. The rotor switches a high sparking voltage to the spark plugs so that these fire in correct sequence.

The distributor cap is a prime example of a component that eventually succumbs to heat and vibration. But even if its bakelite housing has not broken or cracked, carbon deposits and eroded metal terminals can cause distributor-cap failure. However it is a fairly easy and inexpensive part to replace.

The distributor cap has one post for each cylinder and in points ignition systems there is a central post for the coil voltage coming into the distributor. In HEI (High Energy Ignition) systems where there is not a central post, the ignition coil sits on top of the distributor. On the inside of the cap there is a terminal that corresponds to each post and the plug terminals are arranged around the circumference of the cap according to the firing order in order to send the secondary voltage to the proper spark plug at the right time.

The "rotor" head is attached to the top of the distributor shaft which is driven by a gear on the engine's camshaft and thus synchronized to it. This rotor is pressed against a carbon brush on the center terminal of the distributor cap which connects to the ignition coil either through the top and wired directly to the coil in HEI systems; or via the center terminal in points ignition systems and remotely connected to the coil. The rotor is constructed such that the center tab is electrically connected to its outer edge so the voltage coming in to the center post will travel through the carbon point to the outer edge of the rotor. As the camshaft rotates, the rotor spins and its outer edge passes each of the internal plug terminals to fire each spark plug.


Direct ignition

Modern engine designs are tending to do away with the distributor and coil, instead performing the distribution function in the primary circuit electronically and applying the primary (low-voltage) pulse to individual coils on top of each spark plug (Direct Ignition or coil-on-plug). This avoids the need to switch very high voltages, which is very often a source of trouble, especially in damp conditions.

Engine configuration

Engine configuration is an engineering term for the layout of the major components of an internal combustion engine. These components include cylinders, pistons, crankshaft or crankshafts and camshaft or camshafts.

For many automobile engines, the term block is interchangeable with engine in this context, for example V block and V engine can often be used interchangeably in American English. This is because the most common forms are all based on a combined engine block and crankcase that are milled from a single piece of cast metal. The locations of the major components are largely determined by the shape of this one component.

The standard names for some configurations are historic, arbitrary, or both, with some overlap. For example, the cylinder banks of a 180° V engine do not in any way form a V, but it is regarded as a V engine because of its crankshaft and big end configuration, which result in performance characteristics similar to a V engine. But it is also considered a flat engine because of its shape. On the other hand, some V-twin engines which have none of the typical V engine crankshaft design features and consequent performance characteristics are also regarded as V engines, purely because of their shape. Similarly, the Volkswagen VR6 engine is a hybrid of the V engine and the straight engine, and can not be definitively labeled as either. The names W engine and rotary engine have each been used for several unconnected designs. The H-4 and H-6 engines produced by Subaru are not H engines at all, but boxer engines.


Categorisation by piston motion

Engine types include:

* Single cylinder engines

* Inline engine designs:
o Straight engine, with all of the pistons are placed in a single row
o V engine, with two banks of cylinders at an angle, most commonly 60 or 90 degrees.

o Flat engine, two banks of cylinders directly opposite each other on either side of the crankshaft.

o H engine, two crankshafts.

o W engine. Can be both 3 banks and 4 banks.

o Square engine.

o Opposed piston engine, with multiple crankshafts, an example being:
+ Delta engines, with three banks of cylinders and three crankshafts
o U engine, two separate straight engines with crankshafts linked by a central gear.

o X engine.

* Radial designs, including most:

o Rotary engine designs.

* Pistonless rotary engines, notably:

o Wankel engine.


Other categorisations

The majority of four stroke engines have poppet valves although some aircraft engines had sleeve valves. Valves may be located in the cylinder block (side valves) or in the cylinder head (overhead valves). Modern engines are invariably of the latter design. There may be two, three or four valves per cylinder. ie exhaust and inlet valves.

Poppet valves are opened by means of a camshaft which revolves at half the crankshaft speed. This can be either chain, gear or toothed belt driven from the crankshaft and can be located in the crankcase (where it may serve one or more bank of cylinders) or in the cylinder head. There may be one or two camshafts in a cylinder head. If the camshaft is located in the crankcase, a valve train of pushrods and rockers will be required to operate overhead valves. With the side valve arrangement, the valve stems rested on the camshaft. This is a very simple mechanical arrangement but the gas flows within the cylinder head with the side valve arrangement is very poor. If the camshaft(s) is/are located in the cylinder head, the valvetrain will be shorter, no pushrods being required. Some single camshaft designs, still have a rocker. This facilates adustment of mechanical clearances. If there are two camshafts in the cylinder head, (DOHC, double overhead cam)the cams normally bear directly on to the valve stems. This is the usual arrangement for a four-valves-per-cylinder design. This latter arrangement is the most inertia free, allows the most unimpeded gas flows in the engine and is the usual arrengement for high performance automobile engines. It also permits the spark plug to be located in the centre of the cylinder head, which promotes better combustion characteristics. Very large engines eg marine engines can have either extra camshafts or extra lobes on the camshaft to enable the engine to run in either direction.

Cylinder bank

Piston engines are typically arranged with their pistons in rows, moving inside individual cylinders. This allows the engine block to be built from a single piece of metal, which is machined. Engines often have more than one row of pistons, each with their own block, and these are referred to as cylinder banks.

Note that not all engine configurations have cylinder banks. Radial engines have each piston in a separate cylinder, and this was common in earlier in-line engine designs as well.

Vehicle clutche

There are many diferent vehicle clutch designs but most are based on one or more friction discs, pressed tightly together or against a flywheel using springs. The friction material is very similar to the material used in brake shoes and pads and contained asbestos in the past. Also, clutches found in heavy duty applications such as trucks and competition cars use ceramic clutches that have a greatly increased friction coefficient, however these have a "grabby" action and are unsuitable for road cars. The spring pressure is released when the clutch pedal is depressed thus either pushing or pulling the diaphragm of the pressure plate, depending on type, and the friction plate is released and allowed to rotate freely.

While engaging the clutch, the engine speed may need to be increased from idle, using the manual throttle, so that the engine does not stall (although in most cars, especially diesels, there is enough power at idling speed that the car can move although fine movements with the clutch are needed). However, raising the engine speed too high will cause excessive clutch plate wear and cause a harsh, jerky start. This kind of start is desired in drag racing and other competitions, however.


Wet and dry clutches

A 'wet clutch' is immersed in a cooling lubricating fluid, which also keeps the surfaces clean and gives smoother performance and longer life. A 'dry clutch', as the name implies, is not bathed in fluid that robs it of some energy. Since the surfaces of a wet clutch can be slippery (as with a motorcycle clutch bathed in engine oil), stacking multiple clutch disks can compensate for slippage. Most Moto Guzzi and BMW motorcycles use a triple plate clutch like a car.


Clutch operation in automobiles

In a car it is operated by the left-most pedal using hydraulics or a cable connection from the pedal to the clutch mechanism. Even though the clutch may physically be located very close to the pedal, such remote means of actuation are necessary to eliminate the effect of slight engine movement, engine mountings being flexible by design. With a rigid mechanical linkage, smooth engagement would be near-impossible, because engine movement inevitably occurs as the drive is "taken up". No pressure on the pedal means that the clutch plates are engaged (driving), while depressing the pedal will disengage the clutch plates, allowing the driver to shift gears.

A manual transmission contains cogs for selecting gears. These cogs have matching teeth, called dog teeth, which means that the rotation speeds of the two parts have to match for engagement. This speed matching is achieved by a secondary clutch called a synchronizer, a device that uses frictional contact to bring the two parts to the same speed, and a locking mechanism called a blocker ring to prevent engagement of the teeth (full movement of the shift lever into gear) until the speeds are synchronized.


Non-powertrain clutches in automobiles

There are other clutches found in a car. For example, the radiator fan may have a clutch that is heat-activated. The driving and driven elements are separated by a silicone-based fluid. When the temperature is low, the fluid is thin and so the clutch slips. When the temperature is high, the fluid thickens, causing the fan to spin.


Clutch operation in motorcycles

On most motorcycles, the clutch is operated by the clutch lever, located on the left handlebar. No pressure on the lever means that the clutch plates are engaged (driving), while pulling the lever back towards the rider will disengage the clutch plates, allowing the rider to shift gears. Some cars and mopeds have a centrifugal clutch, using centrifugal forces to engage the clutch above certain rpm, see Saxomat. Racing motorcycles often use slipper clutches to eliminate the effects of engine braking.


Other clutches

A clutch may also be a device on a shaft that will "slip" when higher than normal resistance is encountered on a machine. An example of a clutch such as this may be mounted on the driving shaft of a large grass mower. The clutch will "slip" or "give" if the blades were to hit a rock, stump, or other immobile object.

Supercharger

A supercharger (also known as a blower) is an air compressor used to force more air (and hence more oxygen) into the combustion chamber(s) of an internal combustion engine than can be achieved at ambient atmospheric pressure.

The additional mass of oxygen-containing air that is forced into the engine improves on its volumetric efficiency which allows it to burn more fuel in a given cycle - which in turn makes it produce more power. A supercharger can be powered mechanically by belt, gear, or chain-drive from the engine's crankshaft. It can also be driven by a gas turbine powered by the exhaust gases from the engine. Turbine-driven superchargers are correctly referred to as turbo-superchargers - or more commonly as turbochargers.



Types of supercharger

There are two main types of supercharger defined according to the method of compression, positive displacement and dynamic compressors. The former deliver a fairly constant level of boost regardless of engine speed (RPM), whereas the later deliver increasing boost with increasing engine speed.



Positive displacement

Positive displacement pumps deliver a nearly fixed volume of air per revolution at all speeds (minus leakage which is nearly constant at all speeds for a given pressure and so its importance decreases at higher speeds). The device divides the air mechanically into parcels for delivery to the engine, mechanically moving the air into the engine bit by bit.

Major types of positive displacement pumps include:

* Roots
* Lysholm screw
* Sliding Vane
* Scroll-type supercharger, also known as the G-lader
* Piston
* Wankel

Positive displacement pumps are further divided into internal compression and external compression types.

Roots superchargers are typically external compression only (although high helix roots blowers attempt to emulate the internal compression of the Lysholm screw).

* External compression refers to pumps which transfer air at ambient pressure into the engine. If the engine is running under boost conditions, the pressure in the intake manifold is higher than that coming from the supercharger. That causes a back flow from the engine into the supercharger until the two reach equilibrium. It is the back flow which actually compresses the incoming gas. This is a highly inefficient process and the main factor in the lack of efficiency of roots superchargers when used at high boost levels. The lower the boost level the smaller is this loss and roots blowers are very efficient at moving air at low pressure differentials, which is what they were first invented for (hence the original term "blower").

All the other types have some degree of internal compression.

* Internal compression refers to the air being compressed within the supercharger itself and this compressed air, already at or close to boost level, can be delivered smoothly to the engine with little or no backflow. This is more efficient than backflow compression and allows higher efficiency to be achieved. Internal compression devices usually use a fixed internal compression ratio. When the boost pressure is equal to the compression pressure of the supercharger, the backflow is zero. If the boost pressure exceeds that compression pressure, backflow can still occur as in a roots blower. Internal compression blowers must be matched to the expected boost pressure in order to achieve the higher efficiency they are capable of, otherwise they will suffer the same problems and low efficiency of the roots blowers.

Positive displacement superchargers are usually rated by their capacity per revolution. In the case of the roots blower, the GMC rating pattern is typical. The GMC types are rated according to how many two stroke cylinders, and the size of those cylinders, it is designed to scavenge. GMC has made 2-71 3-71 4-71 and the famed 6-71 blowers. For example a 6-71 blower is designed to scavenge 6 cylinders of 71 cubic inches each and would be used on a two-stroke diesel of 426 cubic inches which is designated a 6-71 and the blower takes this same designation. However because 6-71 is actually the engines designation,the actual displacement is less than the simple multiplication would suggest. A 6-71 actually pumps 339 cubic inches per revolution.

Aftermarket derivatives continue the trend with 8-71 to current 14-71 blowers. From this you can see that a 6-71 is roughly twice the size of a 3-71. GMC also made -53 cubic inch series in 2,3,4,6 and 8-53 sizes as well as a “V71” series for use on engines using a V configuration.



Roots Efficiency map

For any given roots blower running under given conditions, a single point will fall on the map. This point will rise with increasing boost and will move to the right with increasing blower speed. It can be seen that at moderate speed and low boost the efficiency can be over 90%. This is the area in which roots blowers were originally intended to operate and they are very good at it.

Boost is given in terms of pressure ratio which is the ratio of absolute air pressure before the blower to the absolute air pressure after compression by the blower. If no boost is present the pressure ratio will be 1.0 (meaning 1:1) as the outlet pressure equals the inlet pressure. 15 psi boost is marked for reference (slightly above a pressure ratio of 2.0 compared to atmospheric pressure). At 15 psi boost Roots blowers hover between 50% to 58%. Replacing a smaller blower with a larger blower moves the point to the left. In most cases, as the map shows, this will moves it into higher efficiency areas on the left as the smaller blower likely will have been running fast on the right of the chart. Usually, using a larger blower and running it slower to achieve the same boost will give an increase in compressor efficiency.

The volumetric efficiency of the roots type blower is very good. Usually staying above 90% at all but the lowest blower speeds. Because of this, even a blower running at low efficiency will still mechanically deliver the intended volume of air to the engine but that air will be hotter. In drag racing applications where large volumes of fuel are injected with that hot air, vaporizing the fuel absorbs the heat. This functions as a kind of liquid after cooler system.



Dynamic

Dynamic compressors rely on accelerating the air to high speed and then exchanging that velocity for pressure by diffusing or slowing it down.

Major types of dynamic compressor are:

* Centrifugal
* Multi stage axial flow

-Comprex superchargers do not fit neatly into either dynamic or positive displacement categories. The Comprex design uses the exhaust gas to directly compress the incoming charge.



Supercharger drive types

Superchargers are further defined according to their method of drive (mechanical - or turbine).

Mechanical:

* Belt(V belt, Toothed belt, Flat belt)
* Direct drive
* Gear drive
* Chain drive

Exhaust gas turbines:

* Axial turbine
* Radial turbine

All types of compressor may be mated to and driven by either gas turbine or mechanical linkage. Dynamic compressors are most often matched with gas turbine drives due to their similar high-speed characteristics, while positive displacement pumps usually use one of the mechanical drives. However, all of the possible combinations have been tried with various levels of success.



Automobiles

In cars, the device is used to increase the "effective displacement" and volumetric efficiency of an engine, and is often referred to as a blower. By pushing the air into the cylinders, it is as if the engine had larger valves and cylinders, resulting in a "larger" engine that weighs less.

In 1900 Gottlieb Daimler (of Daimler-Benz / Daimler-Chrysler fame) became the first person to patent a forced-induction system for internal combustion engines. His first superchargers were based on a twin-rotor air-pump design first patented by American Francis Roots in 1860. This design is the basis for the modern Roots type supercharger.

It wasn't long before the supercharger was applied to custom racing cars, with the first supercharged production vehicles being built by Mercedes and Bentley in the 1920s. Since then superchargers (as well as turbochargers) have been widely applied to both racing and production cars, although their complexity and cost have largely relegated the supercharger to pricey performance cars.

Boosting, or adding a supercharger to a stock naturally-aspirated engine, has made a comeback in recent years due largely to the increased quality of the alloys and machining used in modern engines. In the past, boosting would dramatically shorten engine life due to the extreme temperature and pressure created by the supercharger, but modern engines produced with modern materials provide considerable overdesign; thus, boosting is no longer a serious reliability concern. For this reason boosting is commonly used in smaller cars, where the added weight of the supercharger is less than the weight of a larger engine delivering the same amount of power. This also results in better gas mileage, as mileage is often a function of the overall weight of the car, a sizeable percentage of which is weight of the engine. Nevertheless, adding boost to a car will often void the drivetrain warranty. Also, improperly installed or excessive boost will greatly reduce the life expectancy of the engine, the differential and transmission (which may not have been designed to cope with additional torque).



Supercharging and Turbocharging

The term supercharging technically refers to any pump that forces air into an engine - but in common usage, it refers to pumps that are driven directly by the engine as opposed to turbochargers that are driven by the pressure of the exhaust gasses.

Positive displacement superchargers may absorb as much as a third of the total crankshaft power of the engine, and in many applications are less efficient than turbochargers. In applications where engine response and power is more important than any other consideration, such as top-fuel dragsters and vehicles used in tractor pulling competitions, positive displacement superchargers are extremely common. Superchargers are generally the reason why tuned engines have a distinct high-pitched whine upon acceleration. Cars that whine in this way include the Ford Mustang Cobra, Mercedes SLR and the MINI Cooper S.

There are three main styles of supercharger for automotive use:

* Centrifugal turbochargers - driven from exhaust gasses.

* Centrifugal superchargers - driven directly by the engine via a belt-drive.

* Positive displacement pumps (such as the Roots and the Lysholm (Whipple) blowers).

The thermal efficiency, or fraction of the fuel/air energy that is converted to output power, is less with a mechanically driven supercharger than with a turbocharger, because turbochargers are using energy from the exhaust gases that would normally be wasted. For this reason, both the economy and the power of a turbocharged engine are usually better than with superchargers. The main advantage of an engine with a mechanically driven supercharger is better throttle response, as well as the ability to reach full boost pressure instantaneously. With the latest Turbo Charging technology, throttle response on turbocharged cars is nearly as good as with mechanical powered superchargers, but the existing lag time is still considered a major drawback. Especially considering that the vast majority of mechanically driven superchargers are now driven off clutched pulleys, much like an air compressor.

Roots blowers tend to be 40-50% efficient at high boost levels. Centrifugal Superchargers are 70-85% efficient. The Lysholm style blowers are nearly as efficient as their Centrifugal counterparts.

Keeping the air that enters the engine cool is an important part of the design of both superchargers and turbochargers. Compressing air makes it hotter - so it is common to use a small radiator called an intercooler between the pump and the engine to reduce the temperature of the air.

Picking any method of compression that cannot support the mass of airflow needed for the engine creates excessive heat in the air/fuel charge temperatures. This is true with all forms of supercharging. It is critical to not undersize the component.

Turbochargers also suffer (to a greater or lesser extent) from so-called turbo-lag in which initial acceleration from low RPM's is limited by the lack of sufficient exhaust gas pressure. Once engine RPM is sufficient to start the turbo spinning, there is a rapid increase in power as higher turbo boost causes more exhaust gas production - which spins the turbo yet faster, leading to a belated "surge" of acceleration. This makes the maintenance of smoothly increasing RPM far harder with turbochargers than with belt-driven superchargers which apply boost in direct proportion to the engine RPM.

Turbo-lag is often confused with the term Turbo-spool. Turbo Lag refers to how long it takes to spool the turbo when there is sufficient engine speed to create boost. This is greatly affected by the specifications of the turbocharger. If the turbocharger is too large for the powerband that is desired, needless time will be wasted trying to spool the turbocharger.

By correctly choosing a turbocharger for its use, response time can be improved to the point of being nearly instant. Many well-matched turbochargers can provide boost at cruising speeds.

Centrifugal turbochargers suffer from a form of turbo spool. Due to the fact that the turbine speed is directly proportional to the RPM, pressure and flow output at low RPM is limited, thus it is possible for the demand to outweigh the supply and a vacuum is created until the turbine reaches its compression threshold.



Sequential, Twin and Compound turbochargers

Many efforts have been made to mitigate the effects of turbo-lag in exhaust-driven turbochargers.

Sequential Turbo Charging was used on the Toyota Supra. The MKIV Toyota Supra uses two equally sized turbos. At low RPMs the exhaust gas is flowed through solely the first turbo. Once the boost pressure reaches a pre-set level, the exhaust gas flow is directed through both turbos equally. These two small turbos are then operating in parallel.

An alternative arrangement utilizes two turbochargers of the same size, known as a "Twin-turbo". Twin Turbo Charging can make more power than a single turbo of the same output for two reasons. One is the lower rotating mass of two smaller turbos versus one large turbo, which allows the compressor to spin up to speed much more quickly. The second is the increased exhaust outlet area available for the exhaust gas to flow out of the twin turbo exhaust manifold. Increased exhaust flow will increase power in most situations.

Another style of turbo charging is called "Compound Turbo charging". This is gaining popularity for diesel engines. Tractor engines which compete in tractor pulling use compound turbo charging in some classes. Compound Turbo Charging can create boost levels above 200psig. Compound turbochargers are set up in various fashions. The most popular set up is to use one smaller and one larger turbo. The larger turbo compressor blows into the smaller turbo compressor. The exhaust is set up to first enter the turbine of the smaller turbo, and then into the turbine of the larger turbo. Compound Turbo Charging has little "turbo lag" and can create high power levels.

There are also acts of combining both turbocharging, and a positive displacement supercharger. By compressing air first in the turbocharger, and feeding it to the supercharger. By running more compression in the turbocharger, efficiency is improved as superchargers are less efficient.

Still other combinations are possible - there are after-market kits for several supercharged cars to add a turbocharger either before, after or in parallel with the supercharger. In this manner the supercharger operates alone at lower RPM's and the turbo either takes over from - or adds to the supercharger once there is sufficient exhaust gas pressure available.

Fuel filter

Found in most internal combustion engines, a fuel filter is a filter in the fuel line that screens out dirt and rust particles from the fuel.

Fuel filters serve a vital function in today's modern, tight-tolerance engine fuel systems. Unfiltered fuel may contain several kinds of contamination, for example paint chips and dirt that has been knocked into the tank while filling, or rust caused by moisture in a steel tank. If these substances are not removed before the fuel enters the system, they will cause rapid wear and failure of the fuel pump and injectors, due to the abrasive action of the particles on the high-precision components used in modern injection systems. Fuel filters also improve performance, as the less contaminants in the fuel, the more efficiently it can be burnt.

Fuel filters need to be maintained at regular service intervals. This is usually a case of simply disconnecting the filter from the fuel line and replacing it with a new one, although some specially designed filters can be cleaned and reused many times. If a filter is not replaced regularly it may become clogged with contaminants and cause a restriction in the fuel flow, causing an appreciable drop in engine performance as the engine struggles to draw enough fuel to continue running normally.

Some filters, especially found on diesel engines, consist of a bowl-like design which will collect water in the bottom (as water is more dense than diesel). The water can then be drained off when required, by opening a valve in the bottom of the bowl and letting the water run out, until the bowl contains only diesel. It is especially undesirable for water to be drawn into a diesel engine fuel system, as the system relies on the diesel for lubrication of the moving parts, and if water gets into a moving part which requires constant lubrication (for example an injector valve), it will quickly cause overheating and unnecessary wear. This type of filter may also include a sensor, which will alert the operator when the filter needs to be drained. In automobiles this usually causes an idiot light (customarily orange, and with the image of a fuel filter) on the dashboard to illuminate.

Exhaust pipe

An exhaust pipe is usually tubing used to guide waste exhaust gases away from a controlled combustion inside an engine or stove.

An exhaust pipe must be carefully designed to carry toxic and/or noxious gases away from the users of the machine. Indoor generators and furnaces can quickly fill an enclosed space with carbon monoxide or other poisonous exhaust gases if they are not properly vented to the outdoors. Also, the gases from most types of machine are very hot; the pipe must be heat-resistant, and it must not pass through or near anything which can burn or can be damaged by heat. A chimney serves as an exhaust pipe in a stationary structure.

With a ship's or large boat's onboard below-decks diesel engine:-

* Lagging the exhaust pipe stops it from overheating the engine room where people must work to service the engine.

* Feeding water into the exhaust pipe cools the exhaust gas and thus lessens the back-pressure at the engine's cylinders' exhaust ports and thus helps the cylinders to empty quicker.

An automobile's exhaust system usually connects to the exhaust manifold and usually includes a muffler (British English: silencer) to reduce engine noise, and often in recent years a catalytic converter to reduce the emissions that contribute to air pollution.

In a two-stroke engine, such as that used on dirt bikes, a bulge in the exhaust pipe known as an expansion chamber uses the pressure of the exhaust to create a pump that squeezes more air and fuel into the cylinder during the intake stroke. This provides greater power and fuel efficiency.

On a two-cylinder motorcycle, "siamese exhaust pipes" are where both cylinders blow into the same exhaust pipe. This usage is derived from "Siamese twin".

Most motorcycles' exhaust pipes and their silencers/mufflers, and the heat shields around some trucks' exhaust pipes, are chrome plated and act as display features.

Various Types of Tires

By: James Hunt

Today tires are being designed to suit the needs of every driver. There are tire companies that offer a complete line of tires for passenger vehicles, light trucks and commercial vehicles as well as giant tires for off road performance. Whatever the type of vehicle you have, you can get tires that fir the make and model of your car or truck.

The most common type of tires that people buy is all season tires. These tires feature a special all weather design in the tread so you know that they are dependable in whatever driving conditions you may encounter. These types of tires have deep open groves that provide excellent traction in water because these grooves throw the eater away from the long lateral sipes.

There are companies that specialize in making winter tires that use what is called the microbit compound that gives the tires an extra grip on the road. These tires have a new unidirectional pattern in the tread for better traction when driving in snow. There are other tires that are made specially for driving on ice and in slippery conditions. These tires usually are more expensive then all season tires as they are made for a certain time of the year.

There are certain tire and wheel companies that create tires for light trucks that feature a compute-designed variable pitch tread so that that there is less noise when you are driving. They have a deep traction tread and a special shoulder block design for improved grip in wet or snowy driving conditions. The wear on the tires is minimized by an optimized design with open lateral sipes and a proper tread radius so that the tires receive a more uniform wear. The light truck tires are constructed with high ply turn up so that the response from the steering wheel is enhanced, giving the truck better stability when carrying a heavy load.

Article Source: http://www.articlerich.com

James Hunt has spent 15 years as a professional writer and researcher covering stories that cover a whole spectrum of interest. Read more at www.best-in-tires.info

Engine tuning

Engine tuning or engine building is the adjustment, modification or design of internal combustion engines to yield optimal performance, either in terms of power output or economy. It is a popular pastime with amateur mechanics or "gearheads" and "petrolheads". It has a long history, almost as long as the development of the car in general, originating with the development of early racing cars, and later, with the post-war hot-rod movement.

Tuning can describe a wide variety of adjustments and modifications, from the routine adjustment of the carburetor and ignition system to significant engine modifications. On older engines, setting the idling speed, mixture, carburetor balance, spark plug and distributor point gaps and ignition timing were both regular tasks on all engines and the final but essential steps in setting up a racing engine. On modern engines some or all of these tasks are automated.

At the other end of the scale, performance tuning of an engine can involve revisiting some of the design decisions taken at quite an early stage in the development of the engine.


Engine Tune-up

Tune-up describes the normal, routine adjustments -- without modifications -- of the engine to meet the manufacturer's specifications. Tune-ups are periodically needed, for example every 12 months or 19,000 km to ensure an automobile runs as expected. Modern vehicles now often run over 160,000 km (or 10 years) without requiring a tune-up.

Tune-ups may include the following:

* Re-fastening of cylinder head bolts
* Adjustment of the carburetor idle speed and the air-fuel mixture
* Inspection and possible replacement of ignition system components like contact points, distributor cap and rotor button
* Replacement of air filter and other filters
* Inspection of emission controls

The engine manufacturer specifies the schedule and method of engine-tuneup. However, the method tuning car engines goes beyond the manufacturer's suggestions.



Performance tuning

Performance tuning focuses on tuning an engine for motor sport, although many cars built by hobbyists never compete but rather are built for display at motor shows or the simple pleasure of owning and driving such a car. In this context (and depending on the particular event), the power output, torque, and responsiveness of the engine are of premium importance, but reliability and economy are also relevant. To win, a car must complete the event. This means the engine must be strong enough to do so, often far stronger than the production design on which it is based, and also that the vehicle must carry sufficient fuel. The weight of this fuel will affect the overall performance of the car, so fuel economy is a competitive advantage. This also means that the performance tuning of an engine should take place in the context of the development of the overall vehicle. In particular, transmission, suspension and brakes must match the performance of the engine, otherwise the car will be unreliable, uncompetitive, and perhaps extremely dangerous.

In most cases, people are interested in increasing the power output of an engine. Many well tried and tested techniques have been devised to achieve this, but all essentially operate to increase the rate (and to a lesser extent efficiency) of combustion in a given engine. This is achieved by putting more fuel/air mixture into the engine, using a fuel with higher energy content, burning it more rapidly, and getting rid of the waste products more rapidly - this increases volumetric efficiency. The specific ways this is done include:

* Increasing the engine displacement. This can be done by "boring" - increasing the diameter of the cylinders and pistons, or by "stroking" - using a crankshaft with a longer stroke (in combination with pistons of shorter compression height, to maintain the original compression ratio), or both.

* Using larger or multiple carburetors, to create more fuel/air mixture to burn, and to get it into the engine more quickly. In modern engines, fuel injection is more often used, and may be modified in a similar manner.

* Increasing the size of the valves in the engine, thus decreasing the restriction in the path of the fuel/air mixture entering, and the exhaust gases leaving the cylinder. Using multiple valves per cylinder results in the same thing - it is often more practical to have several small valves than have larger single valves.

* Using larger bored, smoother, less contorted intake and exhaust manifolds. This helps maintain the velocity of gases. Similarly, the ports in the cylinder can be enlarged and smoothed to match. This is termed "Cylinder head porting", usually with the aid of an air flow bench for testing and verifying the efficiency of the modifications.

* The larger bore may extend right through the complete exhaust system, using larger diameter piping and low back pressure mufflers, and through the intake system, with larger diameter airboxes and high-flow, high-efficiency air filters. Muffler modifications will change the sound of the car's engine, usually making it louder; for some tuners this is in itself a desirable property.

* Increasing the valve opening height (lift), by changing the profiles of the camshaft or the lift (lever), ratio of the valve rockers (OHV engines), or cam followers (OHC engines).

* Optimising the valve timing to improve burning efficiency - usually this increases power at one range of operating RPM at the expense of reducing it at others. For many applications this compromise is acceptable. Again this is usually achieved by a differently profiled camshaft. See also Four-stroke cycle#Valve Timing, variable valve timing.

* Raising the compression ratio, which makes more efficient use of the cylinder pressure developed and leading to more rapid burning of fuel, by using larger compression height pistons or thinner head gasket, or by milling "shaving" the cylinder head.

* Forced Induction; adding a turbocharger or supercharger. The fuel/air mass entering the cylinders is increased by compressing the air first, usually mechanically.

* Using a fuel with higher energy content or by adding an oxidiser such as nitrous oxide.

* Changing the tuning characteristics electronically, by changing the firmware of the engine management system (EMS). This chip tuning often works because modern engines are designed to give a great deal of raw power, which is then reduced by the engine management system to make the engine operate smoothly over a wider RPM range, with low emissions. By analogy with an operational amplifier, the EMS acts as a feedback loop around an engine with a great deal of open loop gain. Many modern engines are now of this type and amenable to this form of tuning. Naturally many other design parameters are sacrificed in the pursuit of power.

The choice of modification depends greatly on the degree of performance enhancement desired, budget, and the characteristics of the engine to be modified. Intake, exhaust, and chip upgrades are usually amongst the first modifications made as they are the cheapest, make reasonably general improvements (whereas a different camshaft, for instance, requires trading off performance at low engine speeds for improvements at high engine speeds), can often improve fuel economy, generally don't affect engine reliability much (because no moving parts are modified), and are in any case essential to take full advantage of any further upgrades.

* Manufacturer Detuned Engines - Changing the tuning characteristics electronically, by changing the firmware of the engine management system (EMS). This chip tuning also works because many manufacturers produce one engine which is used in a range of models and the power and torque characteristics are determined solely by the engine management system software. This allows the manufacturers to sell cars in various markets with different tax and emissions regulations without the huge development cost of designing different engines. Cross platform engine sharing also allows for a single engine to be used by different brands, tuned to suit their particular market.

Examples of models using one engine with different ECU software providing varying specifications:

The Volvo V70 D5 Euro IV is available as 126 bhp, 163 bhp, and 185 bhp, all sharing the same 2.4 turbo diesel engine. The Mini One and Mini Cooper are available as 90 bhp and 127 bhp respectively, both sharing the same 1.6 normally aspirated engine. The Ford Focus ST225 and Volvo S40 T5 both share the Volvo 2.5 turbo petrol engines, with different power outputs controlled by the engine management system.




Definitions

NOTE: None of these terms necessarily mean new pistons, block line-boring, balancing, etc. The proof is in the fine print. Ask your engine builder for details in writing before committing to purchase engine work.



Overhaul

An engine Overhaul means putting the engine back to factory specifications. This generally involves new piston rings, bearings and gaskets. When done by a competent engine builder, you can be confident the engine will perform as new.



Rebuild

Rebuild is a marketing term with no fixed definition. It is often taken to means a professional overhaul with certain parts replaced with new units whether needed or not. For example some rebuilders will always replace the pistons (which not usually replaced during an overhaul unless damaged).



Re-manufacture

Re-manufactured is a marketing term to mean an engine put together to match factory specifications e.g. "as new". Although often a buyer may take this to mean all-new parts are used, this is never the case. At the very least, the cylinder block will be used, as may most other parts. High-quality rebuilds will often include new pistons and line-boring of the crankshaft and camshaft bores.



Blueprinting

In engine blueprinting, all the specifications are double-checked. Usually this indicates closer-than-factory tolerances, with custom specifications appropropriate for a street car or a race car. The goals usually are to:

* Ensure the engine puts out the rated horsepower (because not all mass-production engines put out the rated horsepower) for its manufacturer's design

or

* Eke more horsepower out of a given engine design, by extra careful measurement and assembly

* balancing of reprocating parts and rotating assemblies, to reduce engine vibrations thus achieving more horsepower due to recover of horsepower "lost" to vibrations

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.

For example, an engine manufacturer may list a piston ring end-gap specification of 0.003 to 0.005 inches for general use in a consumer automobile application. But or an endurance racing engine which runs hot, a "blueprinted" specification of 0.00045 to 0.00050 may be desired. For a drag-racing engine which runs only in short burts, a tight 0.00035 to .00040 inch tolerance may be used instead.

Crossflow cylinder head

A crossflow cylinder head is a cylinder head that features the intake and exhaust ports on opposite sides. The gases can be thought to flow across the head. This is in contrast to reverse-flow cylinder head designs that have the ports on the same side.

A crossflow head gives better performance, but the popular explanation put forward for this — that the gases don't have to change direction and hence are moved into and out of the cylinder more efficiently — is a simplification since there is no continuous flow because of valve opening and closing. But since there is overlap between the intake and exhaust profiles there is a point in which both valves are open. At that point the inertia of the exhaust gases leaving the cylinder helps to aspirate the intake gases into the cylinder. The other main reason for a crossflow's performance is that the ports and valves can be larger and its physical separation of the hot exhaust manifold keeps the air in the intake manifold cooler. Most modern engines are of a crossflow design.

"Crossflow" is often used to refer specifically to Ford Motor Company's Kent Crossflow 4-cylinder OHV engine. This unit has been used in cars from the 1960s up to the present day, albeit with the addition of fuel injection and a modern engine management system.

This term is used for engines which have only one intake and one exhaust valve per cylinder; four (or five) valves per cylinder engines get their superior performance from total port size, not the relative location of the ports, which doesn't have to be mentioned.

Immobiliser

An immobiliser or immobilizer is an electronic device fitted to an automobile which prevents the engine from running unless the correct key (or other token) is present. This prevents the car from being "hot wired" after entry has been achieved.

Immobilisers have been mandatory in all new cars sold in the United Kingdom since 1997 and in Australia since 2001. Early models used a static code in the ignition key (or key fob) which was recognised by an RFID loop around the lock barrel and checked against the vehicle's ECU for a match. If the code is unrecognised, the ECU will not allow fuel to flow and ignition to take place. Later models use rolling codes or advanced cryptography to defeat copying of the code from the key or ECU.

The microcircuit inside the key is activated by a small electromagnetic field which induces current to flow inside the key body, which in turn broadcasts a unique binary code which is read by the automobile's ECU. When the ECU determines that the coded key is both current and valid, the ECU activates the fuel-injection sequence.

In some vehicles, attempts to use an unauthorized or "non-sequenced" key cause the vehicle to activate a timed no-start condition and in some highly advanced systems, even use satellite or mobile phone communication to alert a security firm that an unauthorized attempt was made to code a key.

Coincidentally, this information is often recorded in modern automobile ECUs, which may record many other variables including speed, temperature, driver weight, geographic location, throttle position and yaw angle. This information can be used during insurance investigations, warranty claims or technical troubleshooting.

Add-on immobilisers are available for older cars or vehicles without factory immobilisers. The insurance approval for a self-arming immobiliser is known as "Thatcham 2" after the Motor Insurance Repair Research Centre in Thatcham, Berkshire, England. Approved immobilisers must intercept at least two circuits; typically the low-voltage ignition circuit and the fuel pump circuit. Some may also intercept the low-current starter motor circuit from the key switch to the relay.

Statistics in Australia show that 3 out of 4 vehicle thefts are older cars stolen for joyriding, transport or to commit another crime. Immobilisers are fitted to around 45% of all cars in Australia, but only 7% of those that are stolen. In many instances, where a vehicle fitted with an immobiliser has been stolen, the thief had access to the original key. Only around 1 in 4 vehicles are stolen by professional thieves. The majority of vehicles are stolen by opportunistic thieves relying on finding older vehicles that have ineffective security or none at all. An engine immobiliser will deter opportunistic thieves.

Block heater

A block heater or headbolt heater is an electric heater that heats the engine of a car to ease starting in cold weather. They are connected to normal AC power overnight or before driving, via regular power plugs that are fed through a vehicle's grille. This allows easier starting in cold temperatures, by keeping the coolant warm. Heaters are also available for motor oil so that the oil does not gel and its viscosity remains low. The rapid heat circulation caused by block heaters also aids the initial vaporization of fuel in the engine; because of this effect, block heaters reduce pollution, as poor fuel vaporization causes much higher emissions.

Block heaters are widely used in many northern U.S. states, and are very common in countries with colder climates like Canada and Scandinavia. In colder climates block heaters are often standard equipment in new vehicles. In extremely cold climates, electrical outlets are sometimes found in public or private parking lots, especially in multi-storey car parks. Some parking lots cycle the power on for 20 minutes and off for 20 minutes (e.g. the Light Rail Transit lots for a number of Canadian cities), in order to reduce electricity costs. This results in a decrease in heating effectiveness for the average block heater. However, to what extent this reduces block temperatures in −30 degrees Celsius (−20 degrees Fahrenheit) weather is in question.

Factory installed block heaters are usually inserted into a freeze plug manufacturing hole in the cylinder block, heating the metal, coolant and oil. Although identical heaters are available and can be installed fairly easily, more commonly after market heaters are attached to the oil pan, sometimes with magnets, or a heated dipstick may be used. An alternative to block heaters is a battery warmer which keeps just the battery warm. This maintains the efficiency of the battery, which is highly dependent on temperature, and is cheaper than heating the entire engine block. Heated blankets are available for the entire engine area, as well. A standard timer switch can be used with any of these heaters, so that it does not have to be left on all the time. This can help lower the electrical costs of owning and using a block heater.


Andrew Freeman, a North Dakotan, invented the headbolt heater around 1940 and received a patent for it on November 8, 1949. Before the block heater was invented, people utilized various means of warming engines before starting them, such as pouring hot water on the engine block or draining the engine's oil for storage inside overnight. Some even shoveled hot coals underneath their vehicle's engine to achieve the same effect.

Epicyclic gearing

Epicyclic gearing or planetary gearing is a gear system that consists of one or more outer gears, or planet gears, rotating about a central, or sun gear. Typically, the planet gears are mounted on a movable arm or carrier which itself may rotate relative to the sun gear. Epicyclic gearing systems may also incorporate the use of an outer ring gear or annulus, which meshes with the planet gears.



Gear ratio

The gear ratio in an epicyclic gearing system is somewhat non-intuitive, particularly because there are several ways in which an input rotation can be converted into an output rotation. The three basic components of the epicyclic gear are:

* Sun: The central gear

* Planet carrier: Holds one or more peripheral planet gears, of the same size, meshed with the sun gear

* Annulus: An outer ring with inward-facing teeth that mesh with the planet gear or gears

In many epicyclic gearing systems, one of these three basic components is held stationary; one of the two remaining components is an input, providing power to the system, while the last component is an output, receiving power from the system. The ratio of input rotation to output rotation is dependent upon the number of teeth in each gear, and upon which component is held stationary.

One situation is when the planetary carrier is held stationary, and the sun gear is used as input. In this case, the planetary gears simply rotate about their own axes at a rate determined by the number of teeth in each gear. If the sun gear has S teeth, and each planet gear has P teeth, then the ratio is equal to -S/P. For instance, if the sun gear has 24 teeth, and each planet has 16 teeth, then the ratio is -24/16, or -3/2; this means that one clockwise turn of the sun gear produces 1.5 counterclockwise turns of the planet gears.

This rotation of the planet gears can in turn drive the annulus, in a corresponding ratio. If the annulus has A teeth, then the annulus will rotate by P/A turns for each turn of the planet gears. For instance, if the annulus has 64 teeth, and the planets 16, one clockwise turn of a planet gear results in 16/64, or 1/4 clockwise turns of the annulus. Extending this case from the one above:

* One turn of the sun gear results in − S / P turns of the planets
* One turn of a planet gear results in P / A turns of the annulus

So, with the planetary carrier locked, one turn of the sun gear results in − S / A turns of the annulus.

The annulus may also be held fixed, with input provided to the planetary gear carrier; output rotation is then produced from the sun gear. This configuration will produce an increase in gear ratio, equal to 1+A/S.

These are all described by the equation:

(2 + n)ωa + nωs − 2(1 + n)ωc = 0

where n is the form factor of the planetary gear, defined by:

If the annulus is held stationary and the sun gear is used as the input, the planet carrier will be the output. The gear ratio in this case will be 1/(1+A/S). This is the lowest gear ratio attainable with an epicyclic gear train. This type of gearing is sometimes used in tractors and construction equipment to provide high torque to the drive wheels.

More planet and sun gear units can be placed in series in the same ring gear housing (where the output shaft of the first stage becomes the input shaft of the next stage) providing a larger (or smaller) gear ratio. This is the way some automatic transmissions work.

During World War II, a special variation of epicyclic gearing was developed for portable radar gear, where a very high reduction ratio in a small package was needed. This had two outer annular gears, each half the thickness of the other gears. One of these two annular gears was held fixed and had one fewer teeth than did the other. Therefore, several turns of the "sun" gear made the "planet" gears complete a single revolution, which in turn made the rotating annular gear rotate by a single tooth.


A simpler way to calculate the output RPM from the input RPM

It is first drawn simplified as the sun, a single planet, the ring GEAR, and an arm holding the planet. Any gear can be the input or output, including the arm.

Now, simply plug in the known values and solve for wout:



where N is the number of teeth, w is rpm.

One caveat: if the arm is the input or output, say the ring is the output/input instead and reverse the direction (since if the arm moves a certain speed relative to the ring, the ring moves that same speed the other way relative to the arm, and obviously the arm does not have a tooth count to plug in)

To derive this, just imagine the arm is locked, and calculate the gear ratio wout : win = Nin : Nout, then unlock the arm. From the arms reference frame the ratio is always Nin/Nout, but from your frame all the speeds are increased by the angular velocity of the arm. So to write this relative relationship, you arrive at the equation from above.

Also, make sure Nsun+2Nplanet=Nring where N is the number of teeth. This simply says that the gears will fit, since N is directly proportional to diameter.

Fluid coupling

A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and/or controlled start-up without shock loading of the power transmission system is essential.

A fluid coupling is a sealed chamber containing two toroid shaped impellers immersed in fluid (usually oil). The driving impeller, often referred to as the pump or driving torus (the latter a General Motors automotive term), is rotated by the prime mover, which is typically an internal combustion engine or electric motor. The motion of the pump's radial chambers imparts a relatively complex centripetal motion to the fluid. The moving fluid reaches the center of the driven impeller, referred to as the turbine or driven torus (the latter also a General Motors term), where Coriolis force reaction transfers the angular fluid momentum outward, applying torque to the turbine, thus causing it to rotate in the same direction as the pump. The fluid leaving the outer edges of the turbine returns to the pump, where the cycle repeats.

In automotive applications, the pump is connected to the flywheel of the engine (in fact, the coupling's enclosure may be part of the flywheel proper), and thus is turned by the engine's crankshaft. The turbine is connected to the input shaft of the transmission. As engine speed increases while the transmission is in gear, torque is transferred from the engine to the input shaft by the motion of the fluid, propelling the vehicle. In this regard, the behavior of the fluid coupling strongly resembles that of a mechanical clutch driving a manual transmission.

An important characteristic of a fluid coupling is its stall speed. The stall speed is defined as the highest speed at which the pump can turn when the turbine is locked and maximum input power is applied, a condition which could occur in an automobile if the driver were to fully open the throttle while applying the brakes with a force sufficient to keeping the vehicle from moving. Under stall conditions, all of the engine's power would be dissipated in the fluid coupling as heat, possibly leading to damage.

A fluid coupling cannot achieve 100 percent power transmission efficiency, as some of the energy transferred to the fluid by the pump will be lost to friction (transformed to heat). As a result, the turbine will always spin slower than the pump, this difference increasing with an increase in load on the coupling and/or a decrease in prime mover speed. This speed difference is called slip or slippage.

Also affecting the fluid coupling's efficiency is the fact that the fluid returning from the turbine to the pump is moving in the opposite direction of the pump's rotation, resulting in some braking effect and a good deal of turbulence. This effect substantially increases as the difference between pump and turbine speed increases, causing efficiency to rapidly deteriorate with increasing load.

Generally speaking, the power transmitting capability of a given fluid coupling is exponentially related to pump speed, a characteristic that generally works well with applications where the applied load doesn't fluctuate to a great degree. The torque transmitting capacity of any hydrodynamic coupling can be described by the expression r(N^2)(D^5), where r is the mass density of the fluid, N is the impeller speed, and D is the impeller diameter. In the case of automotive applications, where loading can vary to considerable extremes, r(N^2)(D^5) is only an approximation. Stop-and-go driving will tend to operate the coupling in its least efficient range, causing an adverse effect on fuel economy.

Fluid couplings were used in a variety of early semi-automatic transmissions and automatic transmissions, the largest such application being in the General Motors single, dual range and Jetaway Hydramatic models. Since the late 1940's, the more versatile hydrodynamic torque converter has replaced the fluid coupling in automotive applications. Fluid couplings are still widely used in industrial applications, especially in machine drives that involve high inertia starts or constant cyclic loading.

Automatic transmission

An automatic transmission is an automobile gearbox that can change gear ratios automatically as the car or truck moves, thus freeing the driver from having to shift gears manually. (Similar but larger devices are also used for railroad locomotives.)

Most cars sold in the United States since the 1950s have been equipped with an automatic transmission. This has, however, not been the case in Europe and much of the rest of the world. Automatic transmissions, particularly earlier ones, reduce fuel efficiency and power. Where fuel is expensive and, thus, engines generally smaller, these penalties are more burdensome. In recent years, automatic transmissions have significantly improved in their ability to support high fuel efficiency but manual transmissions are still generally more efficient.

Most automatic transmissions have a set selection of possible gear ranges, often with a parking pawl feature that will lock the output shaft of the transmission.

However, some simple machines with limited speed ranges and/or fixed engine speeds only use a torque converter to provide a variable gearing of the engine to the wheels. Typical examples include forklift trucks and some modern lawn mowers.

Recently manufacturers have begun to make continuously variable transmissions commonly available (earlier models such as the Subaru Justy did not popularize CVT). These designs can change the ratios over a range rather than between set gear ratios. Even though CVTs have been used for decades in a few vehicles (e.g. DAF saloons and the Volvo 340 series that succeeded them, and later the Subaru Justy), the technology has recently gained greater acceptance among manufacturers and customers.



Hydraulic automatic transmissions

It is invented by Makarand Patil ,DET 06.working in Ashok leyland

The predominant form of automatic transmission is hydraulically operated, using a fluid coupling or torque converter and a set of planetary gearsets to provide a range of torque multiplication.

===Parts and operation===A hydraulic automatic transmission consists of the following parts:

* Fluid coupling or torque converter: A hydraulic device connecting the engine and the transmission. It takes the place of a mechanical clutch, allowing the engine to remain running at rest without stalling. A torque converter is a fluid coupling that also provides a variable amount of torque multiplication at low engine speeds, increasing "breakaway" acceleration.

* Planetary gearset: A compound planetary set whose bands and clutches are actuated by hydraulic servos controlled by the valve body, providing two or more gear ratios.

* Valve body: hydraulic control center that receives pressurised fluid from a main pump operated by the fluid coupling/torque converter. The pressure coming from this pump is regulated and used to run a network of spring-loaded valves, check balls and servo pistons. The valves use the pump pressure and the pressure from a centrifugal governor on the output side (as well as hydraulic signals from the range selector valves and the throttle valve or modulator) to control which ratio is selected on the gearset; as the car and engine change speed, the difference between the pressures changes, causing different sets of valves to open and close. The hydraulic pressure controlled by these valves drives the various clutch and brake band actuators, thereby controlling the operation of the planetary gearset to select the optimum gear ratio for the current operating conditions. However, in many modern automatic transmissions, the valves are controlled by electro-mechanical servos which are controlled by the Engine Management System or a separate transmission controller. (See History and improvements below.)

The multitude of parts, along with the complex design of the valve body, originally made hydraulic automatic transmissiondfhndfgs much more complicated (and expensive) to build and repair than manual transmissions. In most cars (except US family, luxury, sport-utility vehicle, and minivan models) they have usually been extra-cost options for this reason. Mass manufacturing and decades of improvement have reduced this cost gap.



History and improvements

Oldsmobile's 1940 models featured Hydra-Matic drive, the first mass-production fully automatic transmissions. Initially an Olds exclusive, Hydra-Matic had a fluid coupling (not a torque converter) and three planetary gearsets providing four speeds plus reverse. Hydra-Matic was subsequently adopted by Cadillac and Pontiac, and was sold to various other automakers, including Bentley, Hudson, Kaiser, Nash, and Rolls-Royce. From 1950 to 1954 Lincoln cars were also available with GM Hydra-Matic. Mercedes-Benz subsequently devised a four-speed fluid coupling transmission that was similar in principle to Hydra-Matic, but did not share the same design.

The first torque converter automatic, Buick's Dynaflow, was introduced for the 1948 model year. It was followed by Packard's Ultramatic in mid-1949 and Chevrolet's Powerglide for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the torque converter for additional gear reduction. In the early 1950s Borg-Warner developed a series of three-speed torque converter automatics for American Motors Corporation, Ford Motor Company, Studebaker, and several other manufacturers in the US and other countries. Chrysler was late in developing its own true automatic, introducing the two-speed torque converter PowerFlite in 1953 and the three-speed TorqueFlite in 1956.

By the late 1960s most of the fluid-coupling four-speeds and two-speed transmissions had disappeared in favor of three-speed units with torque converters. By the early 1980s these were being supplemented and eventually replaced by overdrive-equipped transmissions providing four or more forward speeds. Many transmissions also adopted the lock-up torque converter (a mechanical clutch locking the torque converter impeller and turbine together to eliminate slip at cruising speed) to improve fuel economy.

As the engine computers became more and more capable, even more of the valve body's functionality was offloaded to them. These transmissions, introduced in the late 1980s and early 1990s, remove almost all of the control logic from the valve body, and place it in into the engine computer. (Some manufacturers use a separate computer dedicated to the transmission but sharing information with the engine management computer.) In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather than the spring-loaded valves in the valve body. This allows for more precise control of shift points, shift quality, lower shift times, and (on some newer cars) semi-automatic control, where the driver tells the computer when to shift. The result is an impressive combination of efficiency and smoothness. Some computers even identify the driver's style and adapt to best suit it.

ZF Friedrichshafen AG and BMW were responsible for introducing the first five-speed automatic (the ZF 5HP18 in the 1992 BMW E34 5-Series) and the first six-speed (the ZF 6HP26 in the 2002 BMW E65 7-Series). Mercedes-Benz's 7G-TRONIC was the first seven-speed in 2003, with Toyota Motor Company introducing an 8-speed in 2007 on the Lexus LS 460 and 600.



Automatic transmission modes

In order to select the mode, the driver must move a gear shift lever which can be located on the steering column or on the floor next to the driver. In order to select gears/modes the driver must push a button in (called the shift lock button) or pull the handle (only on column mounted shifters) out.

Automatic Transmissions have various modes depending on the model and make of the transmission. Some of the common modes are:

Park (P) – This selection mechanically locks the transmission, restricting the car from moving in any direction. A pin prevents the transmission from moving forward (although wheels, depending on the drive train, can still spin freely), it is recommended to use the hand brake (or emergency brake) because this actually locks the wheels and prevents them from moving, and increases the life of the transmission and the park mechanism. A car should be allowed to come to a complete stop before setting transmission into park to prevent damage. Park is one of only two selections in which the car can be started. In some cars (notably those sold in the US), the driver must have the footbrake depressed before the transmission can be taken out of park.

Reverse (R) – This puts the car into the reverse gear, giving the ability for the car to back up. In order for the driver to select reverse they must come to a complete stop, and push the shift lock button in and select reverse. Not coming to a complete stop can cause severe damage to the transmission.

Neutral/No gear (N)– This disconnects the transmission from the wheels so the car can move freely under its own weight. This is the only other selection in which the car can be started.

Drive (D)– This allows the car to move forward and accelerate through a range of gears. The number of gears a transmission has depends on the model, but they can commonly range from 3, 4 (the most common), 5, 6 (found in VW/Audi Direct Shift Gearbox), and 8 in the new model of Lexus cars.

* D4 – In Honda and Acura automatics this mode is used commonly for highway use (as stated in the manual) and uses all 4 forward gears.

* D3 – This is also found in Honda and Acura automatics and only uses the first 3 gears and according to the manual it is used for stop & go traffic such as city driving.

* + - and M – This is the manual selection of gears for automatics with Tiptronic. The driver can shift up and down at their will.

Second (2 or S) – This mode limits the transmission to the first two gears, or more commonly locks the transmission in second gear. This can be used to drive in adverse conditions such as snow and ice, as well as climbing or going down hills in the winter time.

First (1 or L) – This mode locks the transmission in first gear only. It will not accelerate through any gear range. This, like second, can be used during the winter season, or towing.

Some cars when put into D will automatically lock the doors or turn on the daytime running lights.


Automatic Transmission Models

Some of the best known automatic transmission families include:

* General Motors — Powerglide, Turbo-Hydramatic 350 and 400, 4L60-E, 4L80-E
* Ford: Cruise-O-Matic, C4, C6, AOD/AODE, E4OD, ATX, AXOD/AX4S/AX4N
* Chrysler: TorqueFlite 727 and 904, A500, A518, 45RFE, 545RFE
* BorgWarner (later Aisin AW)
* ZF Friedrichshafen AG
* Allison Transmission
* Voith Turbo
* Aisin AW; Aisin AW is a Japanese automotive parts supplier, known for its automatic transmissions and navigation systems
* Honda
* Nissan/Jatco

Automatic transmission families are usually based on Ravigneaux, Lepelletier, or Simpson planetary gearsets. Each uses some arrangement of one or two central sun gears, and a ring gear, with differing arrangements of planet gears that surround the sun and mesh with the ring. An exception to this is the Hondamatic line from Honda, which uses sliding gears on parallel axes like a manual transmission without any planetary gearsets. Although the Honda is quite different from all other automatics, it is also quite different from an automated manual transmission.


Continuously variable transmissions

A different type of automatic transmission is the continuously variable transmission or CVT, which can smoothly alter its gear ratio by varying the diameter of a pair of belt or chain-linked pulleys, wheels or cones. Some continuously variable transmissions use a hydrostatic drive consisting of a variable displacement pump and a hydraulic motor to transmit power without gears. CVT designs are usually as fuel efficient as manual transmissions in city driving, but early designs lose efficiency as engine speed increases.

A slightly different approach to CVT is the concept of toroidal CVT or IVT (from infinitely variable transmission). These concepts provide zero and reverse gear ratios.

Some current hybrid vehicles, notably those of Toyota, Lexus and Ford Motor Company, have an "electronically-controlled CVT" (E-CVT). In this system, the transmission has fixed gears, but the ratio of wheel-speed to engine-speed can be continuously varied by controlling the speed of the third input to a differential using an electric motor-generator.


Manually controlled automatic transmissions

Most automatic transmissions offer the driver a certain amount of manual control over the transmission's shifts (beyond the obvious selection of forward, reverse, or neutral). Those controls take several forms:

* Throttle kickdown: Most automatic transmissions include a switch on the throttle linkage that will force the transmission to downshift into the next lower ratio if the throttle is fully engaged. The switch generally only functions up to a certain road speed, so as to prevent a downshift that would overrev the engine. Some transmissions also have a part-throttle kickdown, eliminating the need to "floorboard" the throttle to downshift.

* Mode Selection: Allows the driver to choose between preset shifting programs. For example, Economy mode saves fuel by upshifting at lower speeds, while Sport mode (aka Power or Performance) delays shifting for maximum acceleration. The modes also change how the computer responds to throttle input.

* Low gear ranges: Many transmissions have switches or selector positions that allow the driver to limit the maximum ratio that the transmission may engage. On older transmissions, this was accomplished by a mechanical lockout in the transmission valve body preventing an upshift until the lockout was disengaged; on computer- controlled transmissions, the same effect is accomplished electronically. The transmission can still upshift and downshift automatically between the remaining ratios: for example, in the 3 range, a transmission could shift from first to second to third, but not into fourth or higher ratios. Some transmissions will still upshift automatically into the higher ratio if the engine reaches its maximum permissible speed in the selected range.

* Manual controls: Some transmissions have a mode in which the driver has full control of ratio changes (either by moving the selector or through the use of buttons or paddles), completely overriding the hydraulic controller. Such control is particularly useful in cornering, to avoid unwanted upshifts or downshifts that could compromise the vehicle's balance or traction. "Manumatic" shifters, first popularized by Porsche in the 1990s under the trade name Tiptronic, have become a popular option on sports cars and other performance vehicles. With the near-universal prevalence of electronically controlled transmissions, they are comparatively simple and inexpensive, requiring only software changes and the provision of the actual manual controls for the driver. The amount of true manual control provided is highly variable: some systems will override the driver's selections under certain conditions, generally in the interest of preventing engine damage.

Some automatic transmissions modified or designed specifically for drag racing may also incorporate a transmission brake, or "trans-brake," as part of a manual valve body. Activated by electrical solenoid control, a trans-brake simultaneously engages the first and reverse gears, locking the transmission and preventing the input shaft from turning. This allows the driver of the car to raise the engine rpm against the resistance of the torque converter, then launch the car by simply releasing the trans-brake switch.

Exhaust system

An exhaust system conveys burnt gases from an internal combustion engine and typically includes a collection of exhaust pipes. In the most basic sense, the exhaust system simply vents waste gases from the engine. Depending on the overall system design, the exhaust gas may flow through a turbocharger to increase engine power, a catalytic converter to reduce air pollution, and a muffler to reduce noise.


Terminology


Manifold or header

In most production engines, the manifold is an assembly designed to collect the exhaust gas from multiple cylinders and combine those flows into a single pipe. Manifolds are often made of cast iron in stock production cars, and may incorporate material saving design techniques. Most production manifold designs are manufactured to use the least amount of metal, to occupy the least space necessary, or have the lowest production cost. These design restrictions often result in a design that is cost effective but that does not do the most efficient job of venting the gases from the engine. Inefficiencies generally occur due to the nature of combustion engines and their multiple cylinder banks. Since cylinders fire at different times, exhaust leaves them at different times. This time difference can create pressure waves when gases emerging from one cylinder are not completely vacated through the exhaust system by the time another does. This creates a back pressure and restriction in the engine's exhaust system that can restrict the engine's true performance possibilities.

A header is another name for a manifold, but which specifically refers to an enhanced manifold that has been designed for performance. During design, engineers will create a manifold without regard to weight or cost but instead for optimal flow of the exhaust gases. This design results in a header that is more efficient at scavenging the exhaust from the cylinders. Headers are generally circular steel tubing with bends and folds calculated to make the paths from each cylinder's exhaust port to the common outlet all of equal length, and joined at narrow angles to encourage pressure waves to flow through the outlet, and not back in the direction of the other cylinders. In a set of tuned headers the pipe lengths are carefully calculated to enhance exhaust flow in a particular engine RPM range.

Headers are generally manufactured by aftermarket automotive companies, but sometimes can be purchased from the high performance parts department at car dealerships. Generally, most car performance enthusiasts purchase aftermarket headers made by companies solely focused on producing reliable, cost effective, and well designed headers specifically for their car. Headers can also be custom designed by a custom shop. Due to the advanced materials that some aftermarket headers are made of, this can occasionally cost a lot of money. Luckily, exhaust is one system of a car that can be custom built for any auto, and generally non-specific to the motor or design of your car. The only requirement for producing a performance exhaust system is designing a header that properly makes a solid connection to the engine. This is usually accomplished by correct sizing in the design stage, and the selection of a proper gasket type and size for the engine.

Headers are also called extractors in Australia.


Header-back

Header-back (or header back) refers to the portion of the exhaust system from the outlet of the header to the final vent to open air— everything from the header back. Header-back systems are generally produced as aftermarket performance systems for cars without turbochargers.


Turbo-back

Turbo-back (or turbo back) refers to the portion of the exhaust system from the outlet of a turbocharger to the final vent to open air. Turbo-back systems are generally produced as aftermarket performance systems for cars with turbochargers. Some turbo-back (and header-back) systems replace stock catalytic converters with others having less flow restriction. Some systems eliminate the catalytic converter (sometimes called catless or no kitty), which may or may not be legal depending on geographic location and whether the car will be driven on public roads.


Cat-back

Cat-back (also cat back and catback, and more recently axle back) refers to the portion of the exhaust system from the outlet of the catalytic converter to the final vent to open air. This generally includes the pipe from the converter to the muffler, the muffler itself, and the final length of pipe to open air.

Cat-back exhaust systems are a very popular aftermarket performance enhancement. They generally use larger diameter pipe than the stock system. Good systems will have mandrel-bent turns that allow the exhaust gas to exit with as little back pressure as possible. The mufflers included in these kits are often glasspacks, again to reduce back pressure. If the system is engineered more for show than functionality, it may be tuned to enhance the lower sounds that are lacking from high-RPM low-displacement engines.


Tip

The end of the final length of exhaust pipe where it vents to open air, generally the only visible part, often ends with just a straight or angled cut, but may include a fancy tip. The tip is usually chromed, and is often of larger pipe than the rest of the exhaust system. This produces a final reduction in pressure, as well as prevents rusting of the tips, and can be used to enhance the appearance of the car. These are the least expensive parts of the system.

Air filter

An air filter is a device which removes contaminants, often solid particulates such as dust, pollen, mold, and bacteria from air. Air filters are used in application where air quality is important, notably in building ventilation systems and in engines, such as internal combustion engines, gas compressors, diving air compressors, gas turbines and others.

Some buildings, as well as aircraft and other man-made environments (e.g., satellites and space shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method uses fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favor. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid-dynamics of the air-compressor part of the Gas Turbines.


Climate control air filters

There are four main types of mechanical air filter media: paper, foam, synthetics and cotton.

Air filters are found in most all forced-air heating, ventilation, and air conditioning systems. The efficacy of the air filters in such systems significantly affects the Indoor Air Quality. The [[United States Department of Energy advises that "[Air] Filtration should have a Minimum Efficiency Reporting Value (MERV) of 13 as determined by ASHRAE 5.2.2-1999." There are a variety of different types of HVAC filters available. Many are inexpensive and not very efficient. Some options are panel, pleated, electrostatic, HEPA, electronic and media. ASHRAE recommends (MERV 6 or higher) air filters to lower the amounts of pollen, mold and dust that reaches the wet evaporator coils in air conditioning systems. Wet coils contaminated with high levels of pollen and dust can allow mold colonies to grow.

Polyester and/or glass fibres are commonly used to make web formations used for air filtration. Both materials have high temperature ratings of at least 250°F / 120°C, and are widely used in commercial, industrial and residential applications. Polyester and glass fibres can be blended with cotton or other fibres to produce a wide range of performance characteristics. In some cases Polypropylene, which has a lower temperature tolerance, is used to enhance chemical resistance. Tiny synthetic fibres knows as microfibres are used in many types of HEPA (High Efficiency Particulate Air) filters.

Many in-duct filters for home forced air heating and air conditioning systems are made from plain, loosely-spun fiberglass. These filters are inexpensive, disposable, and come in various densities and sizes. Less-dense filters allow for higher airflow, but do not remove as much dust. Higher density filters remove more particles, but are more expensive and offer more resistance to the air. They also become more quickly "loaded" with contaminants and dust. They are considerably less expensive than pleated-paper filters for the same size.



Automotive air filters

Two main types of air filters are used in automobiles: the combustion air filter, and the cabin air filter. The combustion air filter prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination.

Most modern, fuel-injected vehicles use a pleated paper filter element in the form of a flat panel. This filter is usually placed inside a plastic box connected to the throttle body with a large hose.

Older vehicles that use carburetors or throttle body fuel injection typically use a cylindrical air filter, usually a few inches high and between 6 and 16 inches in diameter. This is positioned above the carburetor or throttle body, usually in a metal or plastic container which may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid.

The cabin air filter is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle's passenger compartment. Some of these filters are rectangular and similar in shape to the combustion air filter. Others are uniquely shaped to fit the available space of particular vehicles' outside-air intakes. Being a relatively recent addition to automobile equipment, this filter is often overlooked and clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream.


Paper

Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The "paper" term is somewhat misleading, as the filter media are considerably different from papers used for writing or packaging, etc. There is a persistent belief amongst tuners, fomented by advertising for aftermarket non-paper replacement filters, that paper filters flow poorly and thus restrict engine performance. In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt.


Foam

Oil-wetted polyurethane foam elements are used in some aftermarket replacement automobile air filters. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-wetted foam in these applications. Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer minimal airflow restriction or very high dirt capacity, the latter property making foam filters a popular choice in off-road rallying and other motorsport applications where high levels of dust will be encountered.


Cotton

Cotton is employed in a small number of aftermarket automotive air filters marketed as high-performance items. In the past, cotton gauze saw limited use in original-equipment automotive air filters.


Oil Bath

An oil bath air cleaner consists of a round base bowl containing a pool of oil, and a round insert which is filled with fibre, mesh, foam, or another coarse filter media. When the cleaner is assembled, the media-containing body of the insert sits a short distance above the surface of the oil pool. The rim of the insert overlaps the rim of the base bowl. This arrangement forms a labyrinthine path through which the air must travel in a series of U-turns: up through the gap between the rims of the insert and the base bowl, down through the gap between the outer wall of the insert and the inner wall of the base bowl, and up through the filter media in the body of the insert. This U-turn takes the air at high velocity across the surface of the oil pool. Larger and heavier dust and dirt particles in the air cannot make the turn due to their inertia, so they fall into the oil and settle to the bottom of the base bowl. Lighter and smaller particles are trapped by the filtration media in the insert, which is wetted by oil droplets aspirated thereinto by normal airflow.

Oil bath air cleaners were very widely used in automotive and small-engine applications until the widespread industry adoption of the paper filter in the early 1960s. Such cleaners are still used in off-road equipment where very high levels of dust are encountered, for oil bath air cleaners can sequester a great deal of dirt relative to their overall size, without loss of filtration efficacy or airflow. However, the liquid oil makes cleaning and servicing such air cleaners messy and inconvenient, they must be relatively large to avoid excessive restriction at high airflow rates, and they tend to increase exhaust emissions of unburned hydrocarbons due to oil aspiration when used on spark-ignition engines.

Diffuser (automotive)

A diffuser, in an automotive context, is usually a shaped section of the car underbody which improves the car's aerodynamic properties by enhancing the transition between the high-velocity airflow underneath the car and the much slower freestream airflow of the ambient atmosphere. It works by providing a space for the underbody airflow to decelerate and expand so that the boundary between the car's airflow and "external" airflow is less turbulent, and it also provides a degree of "wake infill" (the wake being a turbulent area of low pressure that is caused by the passage of the vehicle through the air; this can cause pressure drag).

As the air enters towards the front of the car it accelerates and reduces pressure. There is a second suction peak at the transition of the flat bottom and diffuser. The diffuser then eases this "high velocity" air back to normal velocity and also helps fill in the area behind the race car making the whole underbody a more efficient downforce producing device by reducing drag on the car and increasing downforce.

Diesel particulate filter

A diesel particulate filter, sometimes called a DPF, is device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine, most of which are rated at 85% efficiency, but often attaining efficiencies of over 90%. A diesel-powered vehicle with a filter installed will emit no visible smoke from its exhaust pipe.

In addition to collecting the particulate, a method must be designed to get rid of it. Some filters are single use (disposable), while others are designed to burn off the accumulated particulate, either through the use of a catalyst (passive), or through an active technology, such as a fuel burner which heats the filter to soot combustion temperatures, or through engine modifications (the engine is set to run a certain specific way when the filter load reaches a pre-determined level, either to heat the exhaust gases, or to produce high amounts of NO2, which will oxidize the particulates at relatively low temperatures). This procedure is known as "filter regeneration." Fuel sulfur interferes with many "regeneration" strategies, so almost all jurisdictions that are interested in the reduction of particulate emissions, are also passing regulations governing fuel sulfur levels.


Variants of DPFs

Unlike a catalytic converter which is a flow-through device, a DPF cleans exhaust gas by forcing the gas to flow through the filter. There are a variety of diesel particulate filter technologies on the market. Each is designed around similar requirements:

1. Fine filtration
2. Minimum pressure drop
3. Low cost
4. Mass production suitability
5. Product durability



Cordierite wall flow filters

The most common filter is made of cordierite (a ceramic material that is also used as catalytic converter supports (= cores)). Cordierite filters provide excellent filtration efficiency, are (relatively) inexpensive, and have thermal properties that make packaging them for installation in the vehicle simple. The major drawback is that cordierite has a relatively low melting point (about 1200°C) and cordierite substrates have been known to melt down during filter regeneration. This is mostly an issue if the filter has become loaded more heavily than usual, and is more of an issue with passive systems than with active systems, unless there is a system break down.

Cordierite filter cores look like catalytic converter cores that have had alternate channels plugged - the plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face.



Silicon carbide wall flow filters

The second most popular filter material is silicon carbide, or SiC. It has a higher (1700°C) melting point than cordierite, however it is not as stable thermally, making packaging an issue. Small SiC cores are made of single pieces, while larger cores are made in segments, which are separated by a special cement so that heat expansion of the core will be taken up by the cement, and not the package. SiC cores are usually more expensive than cordierite cores, however they are manufactured in similar sizes, and one can often be used to replace the other.

Silicon carbide filter cores also look like catalytic converter cores that have had alternate channels plugged - again the plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face.



Metal fiber flow through filters

Some cores are made from metal fibers - generally the fibers are "woven" into a monolith. Such cores have the advantage that a current can be passed through the monolith to heat the core for regeneration purposes. Metal fiber cores tend to be more expensive than cordierite or silcon carbide cores, and generally not interchangeable with them.



Paper

Disposable paper cores are used in certain specialty applications, without a regeneration strategy. Coal Mines are common users - the exhaust gas is usually first passed through a water trap to cool it, and then through the filter. Paper filters are also used when a diesel machine must be used indoors for short periods of time, such as on a forklift being used to install equipment inside of a store.



Partial filters

There are a variety of devices that produce over 50% particulate matter filtration, but less than 85%. Partial filters come in a variety of materials. The only commonality between them is that they produce more back pressure than a catalytic converter, and less than a diesel particulate filter. Partial filter technology is popular for retrofit.



Filter usage

A properly designed filter will have little effect on fuel usage, however improper installation can be catastrophic, which is why automobile and truck engine manufacturers have avoided the use of filter technology until now. It was first offered as standard by the French manufacturer PSA Peugeot Citroën in early 2000, and has been a huge success. Slow adoption by the German car industry sparked local protests in March 2005.



Maintenance

Filters require more maintenance than catalytic converters. Engine oil ash builds up on the surface of the inlet face of the filter, and will eventually clog the pores. This increases the pressure drop over the filter, which when it reachs 100 inches of water or higher is capable of causing engine damage. Regular filter maintenance is a necessity.



Regeneration

Regeneration is the process of removing the accumulated soot from the filter. This is done either passively (by adding a catalyst to the filter) or actively. On-board active filter management can use a variety of strategies:

* 1) Engine management to increase exhaust temperature
* 2) A fuel burner to increase the exhaust temperature
* 3) A catalytic oxidizer to increase the exhaust temperature
* 4) Resistive heating coils to increase the exhaust temperature
* 5) Microwave energy to increase the exhaust temperature

All on-board active systems use extra fuel, whether through burning to heat the DPF, or providing extra power to the DPF's electrical system. Typically a computer monitors one or more sensors that measure back pressure and/or temperature, and based on pre-programmed set points the computer makes decisions on when to activate the regeneration cycle. The additional fuel can be supplied by a metering pump. Running the cycle too often while keeping the back pressure in the exhaust system low will use extra fuel. The reverse runs risk of engine damage and/or uncontrolled regeneration and possible DPF failure. Quality regeneration software is a necessity for longevity of the active DPF system.

Diesel particulate matter combusts at when temperaures above 600 degrees celsius are attained. The start of combustion causes a further increase in temperature. In some cases the combustion of the particulate matter can raise temperatures above the structural integrity threshold of the filter material, which can cause catastophic failure of the substrate. Various strategies have been developed to limit this possibility. Note that unlike a spark-ignited engine, which typically has less than 0.5% oxygen in the exhaust gas stream before the emission control device(s), many diesel engines run above 15% oxygen pre-filter. While the amount of available oxygen makes fast regeneration of a filter possible, it also contributes to runaway regeneration problems.

Some applications use off-board regeneration. Off-board regeneration requires operator intervention (i.e. the machine is either plugged into a wall/floor mounted regeneration station, or the filter is removed from the machine and placed in the regeneration station). Off-board regeneration is not useable for on-road vehicles, except in situations where the vehicles are parked in a central depot when not in use. Off-board regenration is mainly used in industrial and mining applications. Coal mines (with the attendant explosion risk from coal damp) use off-board regeneration if non-disposable filters are installed, with the regeneration stations sited in an area where non-permissible machinery is allowed. Many forklift makes also use off-board regeneration - typically mining machinery and other machinery that spend their operational lives in one location, which makes having a stationary regeneration station practical. In situations where the filter is physically removed from the machine for regeneration there is also the advantage of being able to inspect the filter core on a daily basis (DPF cores for non-road applications are typically sized to be useable for one shift - so regeneration is a daily occurrence.



Diesel Oxidation Catalyst (DOC)

DOCs is the other diesel retrofit system. They are devices that use a chemical process to break down pollutants in the exhaust stream into less harmful components.

Airbag design

The air bag system consists of three basic parts-an air bag module, crash sensors and a diagnostic unit. Some systems may also have an on/off switch, which allows the air bag to be deactivated.

The air bag module contains both an inflator unit and the lightweight fabric air bag. The driver air bag module is located in the steering wheel hub, and the passenger air bag module is located in the instrument panel. When fully inflated, the driver air bag is approximately the diameter of a large beach ball. The passenger air bag can be two to three times larger since the distance between the right-front passenger and the instrument panel is much greater than the distance between the driver and the steering wheel.

The crash sensors are located either in the front of the vehicle and/or in the passenger compartment. Vehicles can have one or more crash sensors. The sensors are typically activated by forces generated in significant frontal or near-frontal crashes. Sensors measure deceleration, which is the rate at which the vehicle slows down. Because of this, the vehicle speed at which the sensors activate the air bag varies with the nature of the crash. Air bags are not designed to activate during sudden braking or while driving on rough or uneven surfaces. In fact, the maximum deceleration generated in the severest braking is only a small fraction of that necessary to activate the air bag system.

The diagnostic unit monitors the readiness of the air bag system. The unit is activated when the vehicle's ignition is turned on. If the unit identifies a problem, a warning light alerts the driver to take the vehicle for examination of the air bag system. Most diagnostic units contain a device that stores enough electrical energy to deploy the air bag if the vehicle's battery is destroyed very early in a crash sequence.

Some vehicles without rear seats, such as pick-up trucks and convertibles, or with rear seats too small to accommodate rear-facing child safety seats, have manual ON/OFF switches for the passenger air bag installed at the factory. ON/OFF switches for driver or passenger air bags may also be installed by qualified service personnel at the request of owners who meet government-specified criteria and who receive government permission. An air bag off-switch may be used when an occupant is at risk, this includes: infants riding in rear-facing infant seats in the front passenger seat; children aged 1 to 12 in the front passenger seat; drivers who cannot keep 10 inches between the center of the steering wheel and the center of their breastbone; and people with particular medical conditions.

Initially, most vehicles featured a single airbag, mounted in the steering wheel and protecting the driver of the car (who is the most at risk of injury). During the 1990s, airbags for front seat passengers, then separate side impact airbags placed between the door and occupants, became common.



Triggering conditions

Air bags are typically designed to deploy in frontal and near-frontal collisions, which are comparable to hitting a solid barrier at approximately 8 to 14 miles per hour (mph) (13 to 23 km/h). Roughly speaking, a 14 mph (23 km/h) barrier collision is equivalent to striking a parked car of similar size across the full front of each vehicle at about 28 mph (45 km/h). This is because the parked car absorbs some of the energy of the crash, and is pushed by the striking vehicle. Unlike crash tests into barriers, real-world crashes typically occur at angles, and the crash forces usually are not evenly distributed across the front of the vehicle. Consequently, the relative speed between a striking and struck vehicle required to deploy the air bag in a real-world crash can be much higher than an equivalent barrier crash.

Because air bag sensors measure deceleration, vehicle speed and damage are not good indicators of whether an air bag should have deployed. Occasionally, air bags can deploy due to the vehicle's undercarriage violently striking a low object protruding above the roadway surface. Despite the lack of visible front-end damage, high deceleration forces may occur in this type of crash, resulting in the deployment of the air bag.

The airbag sensor is a MEMS accelerometer, which is a small integrated circuit chip with integrated micromechanical elements. The microscopic mechanical element moves in response to rapid deceleration, and this motion causes a change in capacitance, which is detected by the electronics on the chip, which then sends a signal to fire the airbag. The most common MEMS accelerometer in use is the ADXL-50 by Analog Devices, but there are other MEMS manufacturers as well.

There was some work initially in mercury switches but they did not work very well. Before MEMS, the primary system used to deploy airbags was called a "rolamite". A rolamite is a mechanical device, consisting of a roller suspended within a tensioned band. As a result of the particular geometry and material properties used, the roller is free to translate with very little friction or hysteresis. This device was developed at Sandia National Laboratories. The rolamite and similar macro-mechanical devices were used in air bags until the mid-1990s when they were universally replaced with MEMS.

Most air bags are designed to automatically deploy in the event of a vehicle fire when temperatures reach 300 to 400 degrees Fahrenheit (150 to 200 °C). This safety feature helps to ensure that such temperatures do not cause an explosion of the inflator unit within the air bag module.

Today, airbag triggering algorithms are becoming much more complex. They try to reduce useless deployments (for example, at low speed, no shocks should trigger the airbag to help reduce damage to the car interior in conditions where the seat belt would be an adequate safety device) and to adapt the deployment speed to the crash conditions. The algorithms are considered as very valuable intellectual property. Experimental algorithms may take into account such factors as the weight of the occupant, the seat location, seatbelt use, and even attempt to determine if a baby seat is present.



Deployment mechanism

When there is a moderate to severe frontal crash that requires the frontal air bag to deploy, a signal is sent to the inflator unit within the air bag module. An igniter starts a rapid chemical reaction generating primarily nitrogen gas (N2) to fill the air bag making it deploy through the module cover. Some air bag technologies use compressed nitrogen gas while other technologies use various energetic propellants. Propellants containing sodium azide (NaN3) were very common in early inflator designs. However, propellants containing sodium azide were widely phased out during the 1990s in pursuit of less expensive and less toxic alternatives.

From the onset of the crash, the entire deployment and inflation process is faster than the blink of an eye. Airbags deploy in 1/20 of 1 second. Because a vehicle changes speed so fast in a crash, air bags must inflate rapidly if they are to help reduce the risk of the occupant hitting the vehicle's interior.

Once an air bag deploys, deflation begins immediately as the gas escapes through vents in the fabric. Deployment is frequently accompanied by the release of dust-like particles in the vehicle's interior. Most of this dust consists of cornstarch or talcum powder, which are used to lubricate the air bag during deployment. In older designs, small amounts of sodium hydroxide may initially be present. This chemical can cause minor irritation to the eyes and/or open wounds; however, with exposure to air, it quickly turns into sodium bicarbonate (baking soda). Depending on the type of air bag system, potassium chloride (a table salt substitute) may also be present.

For most people, the only effect the dust may produce is some minor irritation of the throat and eyes. Generally, minor irritations only occur when the occupant remains in the vehicle for many minutes with the windows closed and no ventilation. However, some people with asthma may develop an asthmatic attack from inhaling the dust. With the onset of symptoms, asthmatics should treat themselves as advised by their doctor, then immediately seek medical treatment.

Some airbags in certain car models deploy twice, for two crashes; it first deploys and deflates and may re-inflate.

Air bags must inflate very rapidly to be effective, and therefore come out of the steering wheel hub or instrument panel with considerable force, generally at a speed of about 220 mph. Because of this initial force, contact with a deploying air bag may cause injury. These air bag contact injuries, when they occur, are typically very minor abrasions or burns. The sound of air bag deployment is very loud, in the range of 165 to 175 decibels for 0.1 second. Hearing damage can result in some cases.

More serious injuries are rare; however, serious or even fatal injuries can occur when someone is very close to, or in direct contact with an air bag module when the air bag deploys. Such injuries may be sustained by unconscious drivers who are slumped over the steering wheel, unrestrained or improperly restrained occupants who slide forward in the seat during pre-crash braking, and even properly restrained drivers who sit very close to the steering wheel. Objects must never be attached to an air bag module or placed loose on or near an air bag module, since they can be propelled with great force by a deploying air bag, potentially causing serious injuries.

An unrestrained or improperly restrained occupant can be seriously injured or killed by a deploying air bag. The National Highway Traffic Safety Administration (NHTSA) recommends drivers sit with at least 10 inches (254 mm) between the center of their breastbone and the center of the steering wheel. Children under 12 should always be properly restrained in a rear seat. A rear-facing infant restraint must never be put in the front seat of a vehicle with a front passenger air bag. A rear-facing infant restraint places an infant's head close to the air bag module, which can cause severe head injuries or death if the air bag deploys. Modern cars include a switch to turn off the airbag system of the passenger seat, in which case a child-supporting seat must be installed.



Advanced airbag design

Many advanced air bag technologies are being developed to tailor air bag deployment to the severity of the crash, the size and posture of the vehicle occupant, belt usage and how close that person is to the air bag module. Many of these systems will use multi-stage inflators that deploy less forcefully in stages in moderate crashes than in very severe crashes. Occupant sensing devices let the air bag diagnostic unit know if someone is occupying a seat in front of an air bag, whether the person is an adult or a child, whether a seat belt or child restraint is being used and whether the person is forward in the seat and close to the air bag module. Based on this information and crash severity information, the air bag is deployed at either a high force level, a less forceful level or not at all.

Many new vehicles are also equipped with side air bags. While there are several types of side air bags, all are designed to reduce the risk of injury in moderate to severe side impact crashes. These air bags are generally located in the outboard edge of the seat back, in the door or in the roof rail above the door.

The Citroën C4 provides the first "shaped" driver airbag - made possible by this car's innovative fixed hub steering wheel.

Seat and door-mounted air bags all provide upper body protection. Some also extend upwards to provide head protection. Two types of side air bags, known as inflatable tubular structures and inflatable curtains, are specifically designed to reduce the risk of head injury and/or help keep the head and upper body inside the vehicle. A few vehicles are now being equipped with a different type of inflatable curtain designed to help reduce injury and ejection from the vehicle in rollover crashes.



Airbag landing systems

The first use of airbags for landing were Luna 9 and Luna 13, which landed on the Moon in 1966 and returned panoramic images. The Mars Pathfinder lander employed an innovative airbag landing system, supplemented with aerobraking, parachute, and solid rocket landing thrusters. This prototype successfully tested the concept, and the two Mars Exploration Rover Mission landers employed similar landing systems. The Beagle 2 Mars lander also tried to use airbags for landing, but the landing was unsuccessful for reasons which are not entirely known.

The Airbag

An airbag, also known as a Supplementary/Secondary Restraint System (SRS), an Air Cushion Restraint System (ACRS), or the Supplemental Inflatable Restraint (SIR) is a flexible membrane or envelope, inflatable to contain air or some other gas. Air bags are most commonly used for cushioning, in particular after very rapid inflation in the case of an automobile collision.

Benefits

Air bags supplement the safety belt by reducing the chance that the occupant's head and upper body will strike some part of the vehicle's interior. They also help reduce the risk of serious injury by distributing crash forces more evenly across the occupant's body.

"One recent study concluded that as many as 6,000 lives have been saved as a result of airbags."

However, the exact number of lives saved is almost impossible to calculate.



Costs

Airbags cost about $500 (USD) per vehicle from OEMs, who typically pay the supplier less than $100. If they are deployed in error or stolen, the registered vehicle owner is required to repurchase them. Since they are an integral part of the vehicle design, it is not possible to retrofit airbags to a vehicle that does not have them, with one exception. In the early 90's Breed Technologies of Lakeland Fl, offered a retro driver side system, the SRS-40. These were offered for 7 of the top selling vehicles of the time.

The SRS-40 was a supplemental restraint system. It used a smaller bag, similar to the ones Breed sold in Europe to Fiat and Alfa. Smaller bags were used in Europe, because of the almost 100% usage of seat belts. The smaller bag protected the head and face only.

The SRS-40 system used the same sensor as the early 90's Jeep Cherokee. When the vehicle exceeded a preset negative acceleration threshold for a specific length of time, the sensor released two firing pins, initiating the deployment. This simple all mechanical system eliminated the need for any electrical connections. Sensor calibration was changed from vehicle to vehicle to allow for the structural differences. The kits supplied by Breed included a new steering wheel.

Most manufacturers specify the replacement of undeployed airbags after, for example, 14 years (Volkswagen cars) to ensure their reliability in an accident. Or there may be a notice to inspect after 10 years (Honda cars). If the car is still on the road at this age, it would generally cost far more than the vehicle's market value to have the airbags replaced.

If airbags deploy and the cost of replacing them is more than the total value of the vehicle it is considered a total loss. However, if the vehicle's current worth is greater than the cost of replacing the airbags the vehicle can be saved and driven again.



Airbag Injuries and Fatalities

Airbags involve the extremely rapid deployment of a large cushion. While airbags can protect a person under the right circumstances, they can also injure or kill.

To protect occupants not wearing seat belts, US airbag designs trigger much more quickly than airbags designed in other countries. As seat belt use in the US climbed in the late 1980s and early 1990s, US auto manufactures were able to adjust their designs.

Newer airbags trigger at a lesser speed; nonetheless, passengers must remain at least 25 centimeters (10 in) from the bag to avoid injury from the bag in a crash.

Injuries such as abrasion of the skin, hearing damage (from the sound during deployment), head injuries, eye damage for spectacle wearers and breaking the nose, fingers, hands or arms can occur as the airbag deploys.

In 1990, the first automotive fatality attributed to an airbag was reported, with deaths peaking in 1997 at 53 in the United States. TRW produced the first gas-inflated airbag in 1994, with sensors and low-inflation-force bags becoming common soon afterwards. Dual-depth airbags appeared on passenger cars in 2005. By that time, deaths related to airbags had declined, with no adults deaths and 2 child deaths attributed to airbags that year. Injuries remain fairly common in accidents with an airbag deployment.

Smoking a pipe while driving should be avoided. If the airbag inflates and hits the pipe while it is in the mouth this may well be deadly, even if the impact is only moderate.

The increasing use of airbags has actually made rescue work for Firefighters, EMS and Police Officers more dangerous. Airbags can detonate long after the initial crash, injuring or even killing rescue workers who are inside the car. The addition of side impact airbags to the frame of the car has reduced the number of places that rescue workers can use hydraulic spreader-cutters ("the jaws of life") or other similar cutting tools to remove the car roof, or doors safely. Every first responder should be properly trained on how to safely deactivate airbags or be aware of the potential hazards. Removing the car battery may be a good precaution.

History of the Airbag

There have been airbag-like devices for aeroplanes as early as the 1940s, with the first patents filed in the 1950s.

The airbag as known today was invented by John W. Hetrick in 1952 and he patented the device the following year. Hetrick came up with the idea to help protect his own family using expertise from his naval engineering days.

The American inventor Allen Breed then developed a key component for automotive use - the ball-in-tube sensor for crash detection. He marketed this innovation first in 1967 to Chrysler. During this era, Americans were infrequent users of seat belts and a means of offering seat belt-like levels of occupant protection to unbelted occupants in a head-on collision was felt to be a valuable innovation.

The device was briefly available in the United States in the mid-1970's. Ford built an experimental fleet of cars with airbags in 1971. General Motors followed with a fleet of 1,000 experimental vehicles in 1973, and these Chevrolet cars equipped with dual airbags were sold to the public through GM dealers two years later. GM called this the Air Cushion Restraint System the passenger side air bag in the seventies GM, cars had two-stage deployment similar to newer air bags.

The design is conceptually simple—accelerometers trigger the ignition of a gas generator propellant to very rapidly inflate a nylon fabric bag, which reduces the deceleration experienced by the passenger as they come to a stop in the crash situation. The bag has small vent holes to allow the propellant gas to be (relatively) slowly expelled from the bag as the occupant pushes against it.

Before these Chevrolets were sold, airbags were made available to the public in November 1973 when General Motors began offering dual airbags as an extra-cost option on several 1974 model full size cars made by the Buick, Cadillac and Oldsmobile divisions. This system was known as the Air Cushion Restraint System.

About 12000 vehicles with Airbag were produced by GM and Ford from 1973 to 1976. In 1976, production stopped [1] The standard shoulder belts were removed on these cars as they were designed to replace seat belts in frontal impacts. The passenger side airbag on 1970s cars was located in the lower part of the dashpad and it also acted as a knee restraint. The lower part of the dash on the driver side was also different on cars with air bags as it was padded.

The 1970s fleet of 10,000 airbag-equipped GM experienced seven fatalities. One is now suspected to have been caused by the airbag. The crash severity was only moderate and at the time a heart attack was suspected. The victim was cremated without autopsy.

Then in 1980, Mercedes-Benz introduced the airbag in Germany as an option on its high end Mercedes-Benz W126, which also offered such other exotic options as hydropneumatic suspension. In the Mercedes system, the sensors would tighten the seat belts and then deploy the airbag on impact. The airbag was thus no longer marketed as a means of avoiding seat belts, but as a way to obtain an extra margin of occupant safety.

In 1987 the Porsche 944 turbo became the first car in the world to have driver and passenger airbags as standard equipment. The Porsche 944 and 944S had this as an available option. This year also saw the first airbag in a Japanese car, the Honda Legend.

Airbags became common in the 1980s, with Chrysler and Ford introducing them in the mid-1980s; the former made them standard equipment across its entire line in 1990. The Swedish company Autoliv AB, today Autoliv, was granted a patent on side airbags, and torso side protection airbags were first offered as an option on the 1995 model year Volvo 850. [2] Head protection system airbags were included as standard equipment in the 1998 BMW 7-series.

On July 11, 1984, the U.S. government required cars being produced after April 1, 1989 to have driver's side air bags or automatic seat belts (the automatic seat belt was a technology, now discarded, that "forced" motorists to wear seatbelts). Airbag introduction was stimulated by the U.S. DOT.

In 1998, dual front airbags were mandated by the National Highway Traffic Safety Administration (NHTSA), and de-powered, or second-generation air bags were also mandated. This was due to the injuries caused by first-generation air bags that were designed to be powerful enough to restrain people who were not wearing seatbelts.

Despite the 1970s implementation of airbags in GM cars, many conventional automobiles did not even have them until the mid 1990s.

In 2006, Honda introduced the first motorcycle airbag safety system ever installed on a production motorcycle. The airbag was installed on its Gold Wing motorcycle.

Front air bags are not designed to deploy in side impact, rear impact or rollover crashes. Since air bags deploy only once and deflate quickly after the initial impact, they will not be beneficial during a subsequent collision. Safety belts help reduce the risk of injury in many types of crashes. They help to properly position occupants to maximize the air bag's benefits and they help restrain occupants during the initial and any following collisions.

Although they were touted in the 1960s and 70s as a potential seat belt replacement, automobile airbags are now designed and sold as Supplemental Restraint Systems (SRS); car designers have moved on from the initial view of the airbag as a seat belt replacement.

Aftermarket fuel economy device

An aftermarket fuel economy device is a device sold on the aftermarket that claims to improve the fuel economy and possibly the fuel emissions of a vehicle. There are a large variety of devices sold under names such as "Platinum Gas Saver", "Tornado Fuel Saver", "Cyclone-Z", "Atomized Vapor Injector", or "Turbo-carb".

There are several different designs, but many are designed to fit on the intake or carburetor of a car and purportedly optimize air or fuel flow in some way. They are often sold via late-night infomercials, at prices ranging from $20 to over $100 each.

The US EPA is required to test many of these devices under Section 511 of the Motor Vehicle Information and Cost Savings Act, and to provide public reports on their efficacy. Most devices on the market are not found to improve fuel efficiency to any statistically measurable extent.

Many other reputable organizations such as the AAA and Consumer Reports have performed studies that have found similar results.


Urban legend

There is a related urban legend about an inventor who creates a 100 mpg (2.35L/100km) carburetor, but after demonstrating it for the major vehicle manufacturers, the inventor mysteriously disappears, in which he may have been killed by the government. The urban legend is thought to have started after Charles N. Pogue filed US Patent #1,750,354 for such a device. Though the legend has a basis in reality, it's unlikely that there has been a conspiracy to hide such an invention.

Aftermarket (automotive)

Aftermarket is an umbrella term for the collective network of vendors who design and sell vehicular components that are intended to replace the stock manufacturer's parts. The two main reasons for this are (i) in order to alter the appearance or performance of the vehicle; or (ii) as a straight replacement for a stock item at a lower price, with no intention to cause such a change in appearance or performance.

The criteria used to design a vehicle are based in large part on the features that would sell to the widest audience at a reasonable price for the vehicle's class. Reliability, price, and fuel economy are typically factors in the decision-making process.

The aftermarket has become the means by which one may customize one's vehicle to suit a particular personality (tuning), to provide a role not satisfied by the stock vehicle (i.e. plug in kits available for some hybrid cars), or to simply stand out. Aggressive styling and/or performance enhancements, which might not be important to the average buyer, usually make up a significant portion of the aftermarket. In fact, some parts come bundled together within a larger kit that one may choose to install in order to alter one's vehicle to a more significant degree.

The aftermarket also caters for the wish of many vehicle owners and insurance companies to have access to replacement parts that are less expensive than the official spare parts produced by vehicle manufacturers. The use of aftermarket parts by insurance companies has been a source of controversy. In 1998, an Illinois judge handed down a $1.18 billion judgment against State Farm for the use of aftermarket parts. Little of that judgment was ever paid as the ruling was ultimately reversed by the Illinois Supreme Court in August 2005. According to their website, the Certified Automotive Parts Association (CAPA) is a not-for-profit organization founded in 1987 to organize a program to guarantee and test automotive parts to match the fit, form, function, and quality of Original Equipment Manufacturer (OEM) parts.


Industry

In the United States, in 2004, the automotive aftermarket industry accounted for $257B in sales. The industry employs 4.54 million people in the U.S.

Advanced Parking Guidance System

Advance Parking Guidance System (APGS) is an automatic parking system developed by Toyota Motor Corporation for its latest Lexus models and also the hybrid Prius models. On vehicles equipped with the APGS, via an in-dash screen and button controls, the car will park itself with little input from the user.

The system has received mixed reviews, including a video produced by Automobile Magazine that demonstrates how the system makes parking more difficult. [1] By contrast, a video from CNBC showed the system working "quite effectively" with a first-time user and other reviewers found that the APGS worked smoothly.

* Lexus LS460 L Self Parking Video at YouTube A demonstration of the APGS by Winding Road magazine.

Cylinder (engine)

A cylinder in the central working part of a reciprocating engine, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or iron before precision features are machined into it. (Ceramics have also been tried, so far unsuccessfully.) The cylinders may then be lined with sleeves of some harder metal, or given a wear-resistant coating such as Nikasil. A cylinder's displacement, or swept volume, is its cross-sectional area (the square of half the bore times pi ) times the distance the piston travels within the cylinder (the stroke). The engine displacement is the swept volume of one cylinder times the number of cylinders in the engine.

A piston is seated outside each cylinder by several metal piston rings which fit around its outside surface in machined grooves; typically two for compressional sealing and one to seal the oil. They are made of spring steel and make near contact with the hard walls of the sleeve, riding on a thin layer of lubricating oil which is essential to keep the engine from seizing up. This contact, and the resulting wear, explains the need for the hard lining on the inner surface of the cylinder. The breaking in of an engine is a process whereby tiny irregularities in the metals form congruent grooves. An engine job is a process in which the cylinders are machined out to a slightly larger diameter, and new sleeves and piston rings are installed.



Heat engines

Heat engines, including Stirling engines, are sealed machines using pistons within cylinders to transfer energy from a heat source to a colder reservoir, often using steam or another gas as the working substance. (See Carnot cycle.) The first illustration depicts a cross-section of a cylinder in a steam engine. The sliding part at the bottom is the piston, and the upper sliding part is a poppet valve that directs steam alternately into either end of the cylinder. Refrigerators and air conditioners are heat engines run in reverse, and the noise of the pistons moving inside cylinders is often a nuisance.



Internal combustion engines

Internal combustion engines operate on the inherent volume change accompanying oxidation of gasoline (petrol), diesel fuel (or some other hydrocarbon) or ethanol, an expansion which is greatly enhanced by the heat produced. They are not classical heat engines since they expel the working substance, which is also the combustion product, into the surroundings.

The reciprocating motion of the pistons is translated into crankshaft rotation via connecting rods. As a piston moves back and forth, a connecting rod changes its angle; its distal end has a rotating link to the crankshaft. In addition to cylinder-piston engines, there are also rotary turbines. The Wankel engine is a rotary adaptation of the cylinder-piston concept which has been used by Mazda in automobiles. Rotary engines are relatively quiet because they lack the clatter of reciprocating motion.

Air-cooled engines generally use individual cases for the cylinders to facilitate cooling. Inline motorcycle engines are an exception, having two-, three-, four-, or even six-cylinder air-cooled units in a common block. Water-cooled engines with only a few cylinders may also use individual cylinder cases, though this makes the cooling system more complex. The Ducati motorcycle company, which for years used air-cooled motors with individual cylinder cases, retained the basic design of their V-twin engine while adapting it to water-cooling.

In some engines, especially French designs, the cylinders have "wet liners". They are formed separately from the main casting so that liquid coolant is free to flow around their outsides. Wet-lined cylinders have better cooling and a more even temperature distribution, but this design makes the engine as a whole somewhat less rigid.

A typical four-cylinder automobile engine has a single row of water-cooled cylinders. V engines (V6 or V8) use two angled cylinder banks. The "V" is designed to minimize vibration through destructive interference of harmonic overtones. (The "straight-eight" engine is a thing of the past.) Many other engine configurations exist.

During use, the cylinder is subject to wear from the rubbing action of the piston rings and piston skirt. This is minimized by the thin oil film which coats the cylinder walls, but eventually the cylinder becomes worn and slightly oval in shape, usually necessitating a rebore to an oversize diameter and the fitting of new, oversize pistons. The cylinder does not wear above the highest point reached by the top compression ring of the piston, which can result in a detectable ridge. If an engine is only operated at low rpm for its early life (e.g. in a gently driven automobile) then abruptly used in the higher rpm range (e.g. by a new owner), the slight stretching of the connecting rods at high speed can enable the top compression ring to contact the wear ridge, breaking the ring. For this reason it is important that all engines, once initially run-in, are occasionally "exercised" through their full speed range to develop a tapered wear profile rather than a sharp ridge.

Fuel Injection Detailed function

Note: These examples specifically apply to a modern EFI gasoline engine. Parallels to fuels other than gasoline can be made, but only conceptually.



Typical EFI components

* Injectors
* Fuel Pump
* Fuel Pressure Regulator
* ECM - Engine Control Module; includes a digital computer and circuitry to communicate with sensors and control outputs.
* Wiring Harness
* Various Sensors (Some of the sensors required are listed here.)

* Crank/Cam Position: Hall effect sensor
* Airflow: MAF sensor, sometimes this is inferred with a MAP sensor
* Exhaust Gas Oxygen: O2 Sensor, Oxygen sensor, EGO sensor, UEGO sensor



Functional description

A contemporary EFI system comprises a digital computer "engine control module" (ECM) and a number of sensors to measure the engine's operating conditions. The ECM interprets these conditions in order to calculate the amount of fuel, among numerous other tasks. The desired "fuel flow rate" depends on several conditions, with the engine's "air flow rate" being the fundamental factor.

The electronic fuel injector is normally closed and opens to flow fuel as long as an electric pulse is applied to the injector. The pulse's duration (pulsewidth) is proportional to the amount of fuel desired. The pulse is applied once per engine cycle, which permits pressurized fuel to flow from the fuel supply line, through the open injector, into the engine's air intake, usually just ahead of the intake valve.

Since the nature of fuel injection dispenses fuel in discrete amounts, and since the nature of the 4-stroke-cycle engine has discrete induction (air-intake) events, the ECM calculates fuel in discrete amounts. The injected fuel mass is tailored for each individual induction event. In other words, every induction event, of every cylinder, of the entire engine, is a separate fuel mass calculation, and each injector receives a unique pulsewidth based on that cylinder's fuel requirements.

It is necessary to know the mass of air the engine "breathes" during each induction event. This is proportional to the intake manifold's air pressure/temperature, which is proportional to throttle position. The amount of air inducted in each intake event is known as "air-charge", and this can be determined using one of several methods, but this is beyond the scope of this topic.

Note: The right pedal is not the gas pedal; it is the air pedal. The throttle pedal determines the air, and in turn, the air mass determines the fuel mass. The same is true for carburetors, only carburetors were volume, not mass based devices. With some recent systems, the right pedal isn't even an "air pedal"... it has evolved to a "power demand pedal" - it isn't connected to the throttle at all, it signals the CPU how far the driver has depressed the pedal, and the CPU determines how far to open the throttle using an electric motor. This has many benefits some of which include: controlling emissions during transients, cruise control, traction control, engine start/cranking, driveline clunk, idle speed control, air conditioning load compensation, etc.

The three elemental ingredients for combustion are fuel, air and ignition. However; complete combustion can only occur if the air and fuel is present in the exact stoichiometric ratio, which allows all the carbon and hydrogen from the fuel to combine with all the oxygen in the air, with no undesirable polluting leftovers.

To achieve stoichiometry, the air mass flow into the engine is measured and multiplied by the stoichiometric air/fuel ratio 14.64:1 (by weight) for gasoline. The required fuel mass that must be injected into the engine is then translated to the required pulse width for the fuel injector.

Deviations from stoichiometry are required during non-standard operating conditions such as heavy load, or cold operation, in which case, the mixture ratio can range from 10:1 to 18:1 (for gasoline).

Note: The stoichiometric ratio changes as a function of the fuel; diesel, gasoline, ethanol, methanol, propane, methane (natural gas), or hydrogen.

Also, final pulsewidth is inversely related to pressure difference across the injector inlet and outlet. For example, if the fuel line pressure increases (injector inlet), or the manifold pressure decreases (injector outlet), a smaller pulsewidth will meter the same fuel. Fuel injectors are available in various sizes and spray characteristics as well. Compensation for these and many other factors are programmed into the ECM's software.

In summary, the vehicle operator opens the engine's throttle (right pedal), atmospheric pressure forces air into the engine past sensors that indicate air mass flow. The ECM interprets these signals from the sensors, calculates the desired air/fuel ratio, and then outputs a pulsewidth providing the exact mass of fuel for optimal combustion. This process is repeated every time an intake valve opens.

The modern EFI system treats each injection as a discrete event, which when all strung together, perform one smooth seamless experience. An oversimplified analogy is that it is like a motion picture that appears to move, made from a series of individual images.


Sample pulsewidth calculations

Note: These calculations are based on a 4-stroke-cycle, 5.0L, V-8, gasoline engine. The variables used are real data.


Calculate injector pulsewidth from airflow

First the CPU determines the air mass flow rate from the sensors - lb-air/min. (The various methods to determine airflow are beyond the scope of this topic. See MAF sensor, or MAP sensor.)

* (lb-air/min) × (min/rev) × (rev/4-intake-stroke) = (lb-air/intake-stroke) = (air-charge)

- min/rev is the reciprocal of engine speed (RPM) – minutes cancel.
- rev/4-intake-stroke for an 8 cylinder 4-stroke-cycle engine.

* (lb-air/intake-stroke) × (fuel/air) = (lb-fuel/intake-stroke)

- fuel/air is the desired mixture ratio, usually stoichiometric, but often different depending on operating conditions.

* (lb-fuel/intake-stroke) × (1/injector-size) = (pulsewidth/intake-stroke)

- injector-size is the flow capacity of the injector, which in this example is 24-lbs/hour if the fuel pressure across the injector is 40 psi.

Combining the above three terms . . .

* (lbs-air/min) × (min/rev) × (rev/4-intake-stroke) × (fuel/air) × (1/injector-size) = (pulsewidth/intake-stroke)

Substituting real variables for the 5.0L engine at idle.

* (0.55 lb-air/min) × (min/700 rev) × (rev/4-intake-stroke) × (1/14.64) × (h/24-lb) × (3,600,000 ms/h) = (2.0 ms/intake-stroke)

Substituting real variables for the 5.0 L engine at maximum power.

* (28 lb-air/min) × (min/5500 rev) × (rev/4-intake-stroke) × (1/11.00) × (h/24-lb) × (3,600,000 ms/h) = (17.3 ms/intake-stroke)

Injector pulsewidth typically ranges from 2 ms/engine-cycle at idle, to 20 ms/engine-cycle at wide-open throttle. The pulsewidth accuracy is approximately 0.01 ms; injectors are very precise devices.

Calculate fuel-flow rate from pulsewidth

* (Fuel flow rate) ≈ (pulsewidth) × (engine speed) × (number of fuel injectors)

Looking at it another way:

* (Fuel flow rate) ≈ (throttle position) × (rpm) × (cylinders)

Looking at it another way:

* (Fuel flow rate) ≈ (air-charge) × (fuel/air) × (rpm) × (cylinders)

Substituting real variables for the 5.0 L engine at idle.

* (Fuel flow rate) = (2.0 ms/intake-stroke) × (hour/3,600,000 ms) × (24 lb-fuel/hour) × (4-intake-stroke/rev) × (700 rev/min) × (60 min/h) = (2.24 lb/h)

Substituting real variables for the 5.0L engine at maximum power.

* (Fuel flow rate) = (17.3 ms/intake-stroke) × (hour/3,600,000-ms) × (24 lb/h fuel) × (4-intake-stroke/rev) × (5500-rev/min) × (60-min/hour) = (152 lb/h)

The fuel consumption rate is 68 times greater at maximum engine output than at idle. This dynamic range of fuel flow is typical of a naturally aspirated passenger car engine. The dynamic range is greater on a supercharged or turbocharged engine. It is interesting to note that 15 gallons of gasoline will be consumed in 37 minutes if maximum output is sustained. On the other hand, this engine could continuously idle for almost 42 hours on the same 15 gallons.

Fuel injection

Fuel injection is a means of metering fuel into an internal combustion engine. In modern automotive applications, fuel metering is one of several functions performed by an "engine management system".

For gasoline engines, carburetors were the predominant method to meter fuel before the widespread use of electronic fuel injection (EFI). However, a wide variety of injection systems have existed since the earliest usage of the internal combustion engine.



Differences between carburetors and fuel injection include:

* Fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, but a carburetor relies on the vacuum created by intake air rushing through it to add the fuel to the airstream.

* A carburetor performs several important functions in one single component: it measures engine load, calculates the amount of fuel needed, and adds the required fuel to the airstream. With fuel injection, these functions are performed by separate subsystems and components. This means that each subsystem can be specialized and optimized for its particular role, which brings a number of important performance benefits compared to the compromise solution offered by carburetors.

The carburetor modifications and complexities needed to comply with increasingly-strict US exhaust emission regulations of the 1970s and 1980s gradually eroded and then reversed the simplicity, cost, and packaging advantages carburetors had traditionally offered. Fuel injection appeared first on American-made cars in the late 1950s (the Rochester Fuel Injected Chevrolet Corvette, manufactured from 1957 through 1965), and later in European-made cars in the late 1960s. It was phased in through the latter '70s and '80s at an accelerating rate, with the US and German markets leading and the UK and Commonwealth markets lagging somewhat, and since the early 1990s, almost all gasoline passenger cars sold in first world markets like the United States, Europe, Japan, and Australia have come equipped with electronic fuel injection (EFI).

The fuel injector is only a nozzle and a valve: the power to inject the fuel comes from further back in the fuel supply, from a pump or a pressure container.


Objectives

The functional objectives for fuel injection systems can vary. All share the central task of supplying fuel to the combustion process, but it is a design decision how a particular system will be optimized. There are several competing objectives such as:

* power output
* fuel efficiency
* emissions performance
* ability to accommodate alternative fuels
* durability
* reliability
* driveability and smooth operation
* initial cost
* maintenance cost
* diagnostic capability
* range of environmental operation

Certain combinations of these goals are conflicting, and it is impractical for a single engine control system to fully optimize all criteria simultaneously. In practice, automotive engineers strive to best satisfy a customer's needs competitively. The modern digital electronic fuel injection system is far more capable at optimizing these competing objectives than a carburetor.


Benefits

An engine's air/fuel ratio must be accurately controlled under all operating conditions to achieve the desired engine performance, emissions, driveability, and fuel economy. Modern EFI systems meter fuel very precisely, and when used together with an Exhaust Gas Oxygen Sensor (EGO sensor), they are also very accurate. The advent of digital closed loop fuel control, based on feedback from an EGO sensor, let EFI significantly outperform a carburetor. The two fundamental improvements are:

1. Reduced response time to rapidly changing inputs, e.g., rapid throttle movements.

2. Deliver an accurate and equal mass of fuel to each cylinder of the engine, dramatically improving the cylinder-to-cylinder distribution of the engine.


Those two features result in these performance benefits:

* Exhaust Emissions
o Significantly reduced "engine out" or "feedgas" emissions (the chemical products of engine combustion).

o A reduction in the final tailpipe emissions (≈ 99.9%) resulting from the ability to accurately condition the "feedgas" to make the catalytic converter as effective as possible.


* General Engine Operation
o Smoother function during quick throttle transitions.
o Engine starting.
o Extreme weather operation.
o Reduced maintenance interval.
o A slight increase in fuel economy.

* Power Output

o Fuel injection often produces more power than an equivalent carbureted engine. However, fuel injection alone does not increase maximum engine output. Increased airflow is needed to burn more fuel to generate more heat to generate more output. The combustion process converts the fuel's chemical energy into heat energy, whether the fuel arrived via EFI or via a carburetor. Airflow is often improved with fuel injectors, which are much smaller than a carburetor. Their smaller size allow more design freedom to improve the air's path into the engine. In contrast, a carburetor's mounting options are limited because it is larger, it must be carefully oriented with respect to gravity, and it must be about as far from each of the engine's cylinders. These design constraints generally compromise airflow into the engine.


o A carburetor relies on a drag-inducing venturi to create a local air pressure difference, which forces the fuel into the air stream. The flow loss caused by the venturi is small compared to other flow losses in the induction system. In a well-designed carburettor induction system, the venturi is not a significant airflow restriction.


o Fuel injection is more likely to increase efficiency than power. When cylinder-to-cylinder fuel distribution is improved (common with EFI), less fuel is needed for the same power output. Engine efficiency is known as the BSFC (brake specific fuel consumption). When cylinder-to-cylinder distribution is less than ideal (and it always is under one condition or another, and worse on carburetor systems), more fuel than necessary is metered to the rich cylinders to provide enough fuel to the lean cylinders. Power output is asymmetrical with respect to air/fuel ratio. In other words, burning extra fuel in the rich cylinders does not reduce power nearly as quickly as burning too little fuel in the lean cylinders. The standard fuel metering compromise is to run the rich cylinders "even richer" than the best air/fuel ratio, to provide enough fuel to the leaner cylinders. The net power output improves with all the cylinders making maximum power. An analogy is painting a wall: one coat of paint may not cover the wall properly; a second coat dramatically improves the appearance of the poorly covered areas, but some paint is wasted on areas that were already well covered.


o Deviations from perfect air/fuel distribution, however subtle, affect the emissions, by not letting the combustion events be at the chemically ideal (stoichiometric) air/fuel ratio. Grosser distribution problems eventually begin to reduce efficiency, and the grossest distribution issues finally affect power. Increasingly poorer air/fuel distribution affects emissions, efficiency, and power, in that order.

There are other benefits associated with fuel injection, such as better atomization of the fuel in the intake (constant-choke carburetors have poor atomization at low air speeds, needing modifications such as sequential twin-barrel designs) and better breathing due to eliminating the carburetor's venturi.

Injection systems have evolved significantly since the mid 1980s. Current EFI systems provide an accurate and cost effective method of metering fuel. Emission and subjective performance have steadily improved as modern digital controls came, which is why EFI systems have replaced carburetors in the marketplace.

EFI is becoming more reliable and less expensive through widespread usage. At the same time, carburetors are becoming less available, and more expensive. Even marine applications are adopting EFI as reliability improves. If this trend continues, it is conceivable that virtually all internal combustion engines, including garden equipment and snow throwers, will eventually use EFI.

It should be noted that a carburetor's fuel metering system is a less expensive alternative when there are not strict emission regulations, as in developing countries. EFI will undoubtedly replace carburetors in these nations too as they adopt emission regulations similar to Europe, Japan, and North America.

Turbodiesel

A turbodiesel is a name for a turbocharged Diesel engine. This type of engine was first introduced in a production car in May 1978 in the Mercedes 300SD (series W116, engine OM617.950), only produced for the USA. In Europe its first application was in the Peugeot 604 in early 1979 (model year 1978). Turbocharging is the norm rather than the exception in modern car diesel engines. More modern turbodiesels are the Ford Power Stroke engine series (for Ford F-Series Super Duty trucks, the E-series vans and previously the Excursion SUV) and the Volkswagen and Audi Turbocharged Direct Injection series (for various sedans and SUVs). After a brief lapse between 2000 and 2004 Mercedes reintroduced turbodiesel technology with the introduction of the 2005 E320 CDI. Boasting a 0-100 km/h (0-64mph) time of 6.6 seconds and fuel consumption of 37 mpg, the full year production estimate of 3000 CDIs were ordered within five months. Even more recently, however, Mercedes introduced the BlueTec diesel engine. Offering a 3.0 liter V6, as well as urea injection and particulate filters, the E320 BlueTec has been named the cleanest turbodiesel offered in the United States.

The improvements to power, fuel economy and NVH (Noise, Vibration and Harshness) in both small- and large-capacity turbodiesels over the last decade have spurred their widespread adoption in certain markets, notably in Europe where they (as of 2006) make up over 50% of new car registrations[1]. Turbodiesels are generally considered more flexible for automotive uses than naturally-aspirated diesels, which have strong low-speed torque outputs but lack power at higher speeds. Turbodiesels can be designed to have a more acceptable spread of both power and torque over their speed range or, if being built for commercial use, can be designed to improve either torque or power at a given speed depending on the exact use.

Turbochargers are in many ways more suited to operation in diesel engines. The smaller speed range that Diesel engines work in (between 1000 and 5000 rpm for a private car, and as little as 1000-2500 rpm for a larger unit in a commercial vehicle) mean that the turbocharger has to change speed less, reducing turbo lag and improving efficiency. Diesel engines do not require dump valves (see the turbocharger article for more information) and have lower exhaust temperatures which reduces stress on the turbine blades. The turbodiesel engine can also help with the amount of torque it can give out. Commonly used in trucks, it helps improve the towing capacity of a truck, as well as fuel economy.

Ford Power Stroke engine

The Power Stroke is a family of turbodiesel truck engines sold by Ford Motor Company for the Ford F-Series trucks, the Ford Econoline van, the Ford LCF commercial truck, and the Ford Excursion SUV and built by Navistar International Corporation (International Truck and Engine Corporation).

The Ford Power Stroke name was given to the 7.3 liter diesel engine when they added electronics and direct injection to the 7.3 Liter IDI Turbo engine. Power Strokes are built in two different locations, Indianapolis, Indiana and Huntsville, Alabama. In 2004 the EPA mandated a change in diesel engine emmissions in all registered vehicles for on highway usage. Due to this dramatic change the 7.3 liter Power Stroke has to be laid to rest. In came the 6.0 liter Power Stroke to make its mark on the world. This model will be replaced January 1, 2007. Ford will start using a 6.4 liter engine due to another emmisions change at the beginning of 2007. This new engine bumped the horsepower up to 350 and torque to 650. Many more changes will take place with the usage of the 6.4 liter Power Stroke. Two major changes will be the fuel and oil. The fuel required will be Ultra Low Sulfur Diesel (15 PPM sulfur). The fuel is backwards compatable to the beginning of time. The oil will be classified as CJ-4 vs. the previous CI-4. CJ-4 oil must be used in all diesel engines requiring the USLD and is backwards compatable to approx 12 years for all diesels. (since Ford started using the Power Stroke name). For those of you needing an oil for older trucks you will still be able to get the CI-4 oil.

There have been three different engines offered under the Power Stroke name:

F Series and Excursion Applications

*
o 1994–2003 7.3 L
o 2003–2007 6.0 L
o 2008– 6.4 L

E Series Applications

*
o 1994–2003 7.3 L
o 2004–current 6.0 L


LCF (Low Cab Forward) Application

*
o 2005–current 4.5 L

Power stroke

A power stroke is, in general, the stroke of a cyclic motor which generates force. It is used in describing mechanical engines and molecular motors such as ATP synthase. Many types of motors can be simply described by first, intake stroke (intake of fuel, e.g. gasoline, ATP, etc.) then power stroke and last exhaust stroke (exhaustion of what's left of the fuel which is now in a low energy state), possibly with some steps in between such as the compression stroke in four-stroke cycle engines and then repeating the cycle.

In muscles, the power stroke is the stage of muscle contraction when the cross-bridge (connecting the actin in the thin filament to the myosin in the thick filament) moves towards the H-zone, thus causing the muscle fiber to contract. The energy for this process comes from ATP present in the myosin prior to contraction.

In sports, too, often a swing with a lot of force will be called a power stroke. For example, this is used in canoeing to describe a powerful motion with a paddle.

Flat-12 engine

A flat-12 is an internal combustion engine in a flat configuration, having 12 cylinders.

The flat-12 is larger than a V12 and has no advantage in terms of vibrations, thus the design is rarely used on production cars.

The flat-12 engines are generally are not true horizontally opposed engines (boxer), but rather 180° V-engines. A true boxer has one crank pin per piston, while in the 180° V-engine two pistons share the same crank pin. With twelve cylinders both layouts are perfectly balanced.

The flat design was used in Formula One and Endurance racing. The flat engine concept had the advantage of a low center of gravity. However, when wing-cars requiring air-flow venturis came along in the late 1970s, the wide, flat layout obstructed the airflow and became obsolete.

In 1964-65, at the end of the 1.5 litre F1 era, Ferrari introduced a flat-12 on the Ferrari 1512, but a more classical V12 was chosen for the new 3 litre F1.

The Porsche 917 endurance racing car (introduced in 1969, for the Sport category) was powered by an air-cooled flat-12. This engine was an evolution of the Porsche flat-8 boxer engine and used identical cylinders to those found on the 908, but differed in that it used a V12 type crankshaft.

The domination of the Porsche 917 over the V12-powered Ferrari 512 probably influenced Ferrari, because they returned to the flat-12 in 3 litre water-cooled form for their prototypes and Formula One cars.

The Ferrari flat-12 design was successful and influential especially on Italian manufacturers, including Alfa-Romeo, who were also successful in endurance with a flat-12. The Tecno Formula One flat-12 was a failure, however.

A 4.4-5.0 L 180° V12 was later introduced by Ferrari in some of their production models, including the Berlinetta Boxer and Testarossa.

Flat-6 engine

A flat-6 is a 6 cylinder configuration of a flat engine. The cylinders are laid horizontally, with three on each side. The movement of the pistons in a horizontal engine is all in the same plane, so it creates less vibration than in a V-configuration engine; particularly one with an odd number of cylinders on each side of the engine, like a V6.

Only a few auto makers have used flat-6 engines, among them Tucker in the 1948 Tucker Sedan, Porsche and Subaru. Citroën developed one for the DS but abandoned it due to numerous problems. In the 1960s, Chevrolet made the Corvair with flat-6 air-cooled engines. The shape of the engine suits it better for rear engine designs, where the low center of gravity is an advantage; in front engine designs the width interferes with the ability of the front wheels to steer.

Lycoming developed a very successful series of flat-6 aircraft engines, as used in many Cessna aircraft.

Porsche is well known for its use of flat-6 engines in its Boxster, Cayman, and 911 sports cars. Flat-6 engines are also used in Honda Gold Wing and Honda Valkyrie motorcycles, as well as several Subaru models, including the SVX, Outback, and B9 Tribeca SUV.


The Flat-6 engine of the Honda Valkyrie motorcycle

Flat-4 engine

A flat-4 is a four cylinder internal combustion engine where the cylinders are arranged in a flat configuration, also referred to as horizontally opposed. Flat fours can either be a 180-degree 'V' configuration in which opposing cylinders share a common crank journal, or one in which they have crank journals opposing each other, commonly known as a 'boxer' engine, due to the fact that opposing cylinders reach top dead center simultaneously, and appear to 'punch' one another.

This is not a common configuration, but some brands of automobile have favored such engines and it is a common configuration for smaller aircraft engines such as made by Lycoming or Continental. Although they are considered to be superior to "inline-fours" in terms of vibrations, they have largely fallen out of favor because they have two cylinder banks thus requiring twice as many camshaft than a straight-4 (If an OHC rather than OHV or F-head configuration is used) while the crankshaft is as complex to manufacture. The low center of gravity of the engine is an advantage. The shape of the engine suits it better for mid engine or rear engine designs. With a rear engine body it allows a low-tail body while in front engine designs the width of the engine will interferes with the ability of the front wheels to steer.

The open and exposed design of the engine allows air cooling over water cooling, and in air cooled applications fins are often seen machined into the external cylinder block walls.

Boxer engines are considered to be better balanced than other engine types especially in 4 cylinder configuration.


Automobile use

Jowetts before the 2nd world war were best known for their flat twin engines, but they made a flat four for the Jason and Jupiter models in the 1930s. Post war the Gerald Palmer designed Javelin saloon and Jupiter sports models used a totally different design of flat four. Alec Issigonis originally designed the Morris Minor for a flat four, but cost constraints meant it was never used.

Volkswagen used air-cooled flat-4s extensively in their early days, in the VW Beetle and most early VW designs. Porsche also used the VW engine in the early Porsche 356. This engine was replaced by a Porsche designed flat-4 in the late 356s and the 912. The 914 that replaced the 912 was built in partnership with VW using a VW engine. VW used a water-cooled flat-4 in the third-generation Type 2 until 1991, and until 2005 in the Brazilian version, VW Kombi.

Citroën used an air-cooled flat-4 on the Ami Super, GS, GSA and Axel.

Alfa Romeo introduced a water cooled flat-4 on the Alfa Romeo Alfasud. That engine was later used on the Alfa Romeo Arna, the Alfa Romeo 33, the Alfa Romeo Sprint, the Alfa Romeo 145/146.

Lancia used a water cooled flat-4 on the Flavia and high-end Lancia Gamma.

Subaru produces water-cooled front mounted flat-4 engines marketed as H-4, by which they mean Horizontal rather than the H cross-section normally meant by H engine.


Motorcycle use

The first motorcycle design to use a flat-4 engine was the 996cc 1939 Brough Superior Golden Dream. This fascinating British prototype motorcycle never went into full production due to the advent of World War II.

Honda introduced a liquid cooled flat-4 on a production motorcycle in 1975 on the Honda GL1000 Gold Wing.


Aircraft use

Lycoming developed a very successful series of flat-4 aircraft engines, as used in many Cessna aircraft. Similar engines are produced by Continental Motors.

Flat-twin engine

A flat-twin is a two cylinder internal combustion engine with the cylinders arranged in a flat configuration, often called a Boxer engine. This geometry is thought to be the best for minimizing vibrations in a two cylinder engine. Most of the flat-twin engines built are air cooled.

Flat-twins are used on motorcycles, especially BMWs. The main advantage of this geometry in motorcycles is the superior air cooling of the cylinders. The engine itself will also allow a low center of gravity but this advantage is, in part, balanced by the fact that the engine should be placed rather high in the motorcycle to prevent the cylinders from touching the ground in turns, a side benefit is that the cylinders will prevent the motorcycle from crushing the rider in the event of an accident. In practice a longitudinal V-twin such as on Moto-Guzzi will give a lower center of gravity, but with more vibrations (from odd firing) and less efficient cooling it has different advantages.

In automobiles, the flat-twin was popular on small French cars after World War II. Panhard built some flat-twin engines which were used in competition on DB and CD cars. These engines were known to have a very high power-to-weight ratio despite their rather simple conception. The Citroën 2CV was also powered by a flat-twin. Although the 2CV engine was built with low cost and reliability in mind, the last versions of this engine were relatively powerful (giving 32 hp for 602cc) considering their small engine displacement.

Flat engine

A flat engine is an internal combustion engine with its pistons parallel to the ground. It can be an inline engine canted 90 degrees from straight up, and also can be a boxing engine sometimes referred to as a boxermotor, in which the cylinders are arranged in two banks on either side of a single crankshaft so that the motion of all the pistons is in a single plane.

In 1896, Karl Benz patented his design for the first internal combustion engine with horizontally opposed pistons. There are two main types of these engines:

* The boxer engine, also known as a horizontally opposed engine, in which the corresponding pistons reach top dead centre simultaneously, thus balancing each other with respect to momentum. Flat engines with four or fewer cylinders are most commonly boxer engines. They should not be confused with opposed piston engines which use a very different design.

* The 180° V engine, in which corresponding pistons share a crank pin, and thus each will reach top dead centre half a crankshaft revolution after the other. Flat engines with more than eight cylinders are most commonly V engines.

In German, the term for flat engine is boxermotor, which includes both types, not just those known as boxer engines in English. It is often said that Adolf Hitler supposedly coined the term when he was inspecting the engine of the then new Volkswagen in World War II. When the pistons of the motor are observed from the top they resemble the fists of a boxer as he strikes them together before a bout.

Another source of confusion is the English term horizontally opposed engine, which contrasts with an opposed piston engine, a completely different concept.


Flat engines are more compact than in-line engines, and have a lower center of gravity than any other common configuration. Automobiles and motorcycles powered by a flat engine generally have a lower center of gravity, giving better stability and control. However, these engines are also wider than more traditional configurations and are more expensive to build. The extra width may cause problems in fitting the engine into the engine bay of a front-engined car owing to the interference with the steering wheels, and cornering problems for a motorcycle.

The flat configuration also fits very well with air cooling and aircraft engines. Air-cooled designs such as in the VW Beetle used a flat-4, as did the Porsche 356 and 912. The Chevrolet Corvair used an air-cooled flat-6, a rarity in American designs. Both the older and newer models of the 911 use a flat-6, at first air cooled but later models are water-cooled. These automobiles situate the engine in the rear rather than the front, where its width does not interfere with the steering of the front wheels; the use of air-cooling obviates the need for connecting the engine to a radiator, and also reduces the weight even more.

Front-mounted air-cooled flat-twin engines were used by Citroën in their model 2CV and its derivatives, while the Citroën GS used a flat-4, and a flat-6 was proposed for the Citroën DS but rejected. BMW uses an air-cooled flat-twin in many of their motorbikes.



Boxer engines

Boxer engines of up to eight cylinders have proved highly successful in both automobiles and motorcycles, and continue to be popular for light aircraft engines.

One benefit of using a boxer engine versus a V engine is that the design provides good balance because each piston's momentum is counterbalanced by the corresponding piston movement of the opposite side. These engines can run very smoothly and free of vibrations with a four-stroke cycle, regardless of number of cylinders, and do not require a balance shaft or counterweights on the crankshaft to balance the weight of the reciprocating parts which are required in other engine configurations. But boxer engines tend to produce more noise than inline and V-engines because valve clatter is not so well dampened due to lack of covering by air-filters and other components, and produce a larger torsional vibration than a V engine, and so tend to require a larger flywheel.


Notable boxer engines include:

* In 1896 Karl Benz invented the first internal combustion engine with horizontally opposed pistons.

* In 1923 Max Friz designed the first BMW motorcycles, choosing a 500cc boxer engine and unit transmission with shaft drive.

* The air-cooled flat-4 engine used in the Volkswagen Beetle, SP2 and Karmann Ghia, and later developed further for the Volkswagen Type 2(Bus) transporters and Volkswagen Type 3 cars.

* The air-cooled flat-2 "foot-warmer" motorcycles produced for many years by BMW motorcycles, and as of 2005 now back in their range by popular demand after an attempt to discontinue the design.

* The Citroën 2CV and Panhard air-cooled flat-2 engines, both influenced by the flat-2s of BMW.

* The air-cooled Porsche 911 and Chevrolet Corvair flat-6s.

* The flat-4 engines in Alfa Romeo's Alfasud, Sprint, 33 and early versions of the 145 (last of the line was a 1712 cc flat four, 16 valves, producing up to 137bhp)

* The water-cooled front-mounted flat-4 and flat-6 engines used by Subaru in all of its mid-sized all wheel drive cars. Subaru refers to these as boxer engines in publicity commentary, and include a variety of naturally aspirated and turbo driven engines. In their turbo engines from early 1990 to current, both closed and semi-closed short blocks have been used.

* The water-cooled SOHC 1832cc flat-6 as fitted to the Honda Gold Wing.

* The modern water-cooled Porsche 911 - model numbers 996 and 997, flat-6s

* The Porsche Boxster - model numbers 986 and 987, flat-6s

* The Porsche Cayman - model number 987, flat-6s

* Subaru cars are equipped with boxer engines.

* The engines of light private aircraft are often air-cooled flat-4's and flat-6's of the type famously made by the companies Lycoming, and Continental.


180° V engines

Flat V engines are used in performance and racing cars, normally a 180 degree V12. Ferrari used a 180° version of the Colombo V12 in the Testarossa and Berlinetta Boxer models.

Crosshead bearing

A crosshead bearing (or simply crosshead) is a bearing used in large reciprocating engines, whether internal combustion engines or steam engines.


Usage

On smaller engines the connecting rod links the piston and the crank directly, but this transmits transverse forces to the piston, since the crankpin (and thus the direction the force is applied) moves from side to side with the rotary motion of the crank. These transverse forces are tolerable in a smaller engine; a larger engine's much greater forces would cause an intolerable degree of wear on the piston and cylinder, as well as increasing overall friction in the engine.

In the case of the steam engine, a crosshead is essential if the engine is to be double acting - steam is applied to both sides of the cylinder, which requires a seal on both ends of the cylinder.

A piston rod is attached to the piston and links it to the crosshead, which is a large casting sliding in crosshead guides, allowing it only to move in the same direction as the piston travel. The crosshead is also connected to the rotating crank via the connecting rod. In this way, the transverse forces are applied only to the crosshead and its bearings, not to the piston itself.

Internal combustion engines using crossheads make for easier maintenance of the top end of the engine, since the pistons can be easily removed. The piston rod is mounted on the underside of the piston and connected to the crosshead by a single nut.

Large diesel engines (such as those fitted to ships) often are of this pattern; the vast majority of steam engines are also built this way.

Crossheads in a steam locomotive can be mounted either to one guide mounted above the crosshead or to two, one above and one below (called an alligator crosshead since it has two "jaws"). The former was preferred in many modern locomotives.

History of Jet engines

Jet engines can be dated back to the first century AD, when Hero of Alexandria invented the aeolipile. This used steam power directed through two jet nozzles so as to cause a sphere to spin rapidly on its axis. So far as is known, it was little used for supplying mechanical power, and the potential practical applications of Hero's invention of the jet engine were not recognized. It was simply considered a curiosity.

Jet propulsion only literally and figuratively took off with the invention of the rocket by the Chinese in the 11th century. Rocket exhaust was initially used in a modest way for fireworks but gradually progressed to propel some quite fearsome weaponry; and there the technology stalled for hundreds of years.

The problem was that rockets are simply too inefficient to be useful for general aviation. Instead, by the 1930s, the piston engine in its many different forms (rotary and static radial, aircooled and liquid-cooled inline) was the only type of powerplant available to aircraft designers. This was acceptable as long as only low performance aircraft were required, and indeed all that were available.

However, engineers were beginning to realize conceptually that the piston engine was self-limiting in terms of the maximum performance which could be attained; the limit was essentially one of propeller efficiency. This seemed to peak as blade tips approached the speed of sound. If engine, and thus aircraft, performance were ever to increase beyond such a barrier, a way would have to be found to radically improve the design of the piston engine, or a wholly new type of powerplant would have to be developed. This was the motivation behind the development of the gas turbine engine, commonly called a "jet" engine, which would become almost as revolutionary to aviation as the Wright brothers' first flight.

The earliest attempts at jet engines were hybrid designs in which an external power source supplied the compression. In this system (called a thermojet by Secondo Campini) the air is first compressed by a fan driven by a conventional piston engine, then it is mixed with fuel and burned for jet thrust. The examples of this type of design were the Henri Coandă's Coandă-1910 aircraft, and the much later Campini Caproni CC.2, and the Japanese Tsu-11 engine intended to power Ohka kamikaze planes towards the end of World War II. None were entirely successful and the CC.2 ended up being slower than the same design with a traditional engine and propeller combination.


The key to a practical jet engine was the gas turbine, used to extract energy to drive the compressor from the engine itself. The gas turbine was not an idea developed in the 1930s: the patent for a stationary turbine was granted to John Barber in England in 1791. The first gas turbine to successfully run self-sustaining was built in 1903 by Norwegian engineer Ægidius Elling. The first patents for jet propulsion were issued in 1917. Limitations in design and practical engineering and metallurgy prevented such engines reaching manufacture. The main problems were safety, reliability, weight and, especially, sustained operation.


In 1929, Aircraft apprentice Frank Whittle formally submitted his ideas for a turbo-jet to his superiors. On 16 January 1930 in England, Whittle submitted his first patent (granted in 1932). The patent showed a two-stage axial compressor feeding a single-sided centrifugal compressor. Whittle would later concentrate on the simpler centrifugal compressor only, for a variety of practical reasons.

In 1935 Hans von Ohain started work on a similar design in Germany, seemingly unaware of Whittle's work.

Whittle had his first engine running in April 1937. It was liquid-fuelled, and included a self-contained fuel pump. Von Ohain's engine, as well as being 5 months behind Whittle's, relied on gas supplied under external pressure, so was not self-contained. Whittle's team experienced near-panic when the engine would not stop, even after the fuel was switched off. It turned out that fuel had leaked into the engine and accumulated in pools. So the engine would not stop until all the leaked fuel had burned off. Whittle unfortunately failed to secure proper backing for his project, and so fell behind Von Ohain in the race to get a jet engine into the air.

Ohain approached Ernst Heinkel, one of the larger aircraft industrialists of the day, who immediately saw the promise of the design. Heinkel had recently purchased the Hirth engine company, and Ohain and his master machinist Max Hahn were set up there as a new division of the Hirth company. They had their first HeS 1 engine running by September 1937. Unlike Whittle's design, Ohain used hydrogen as fuel, supplied under external pressure. Their subsequent designs culminated in the gasoline-fuelled HeS 3 of 1,100 lbf (5 kN), which was fitted to Heinkel's simple and compact He 178 airframe and flown by Erich Warsitz in the early morning of August 27, 1939, from Marienehe aerodrome, an impressively short time for development. The He 178 was the world's first jet plane.

Meanwhile, Whittle's engine was starting to look useful, and his Power Jets Ltd. started receiving Air Ministry money. In 1941 a flyable version of the engine called the W.1, capable of 1000 lbf (4 kN) of thrust, was fitted to the Gloster E28/39 airframe specially built for it, and first flew on May 15, 1941 at RAF Cranwell.


One problem with both of these early designs, which are called centrifugal-flow engines, was that the compressor worked by "throwing" (accelerating) air outward from the central intake to the outer periphery of the engine, where the air was then compressed by a divergent duct setup, converting its velocity into pressure. An advantage of this design was that it was already well understood, having been implemented in centrifugal superchargers. However, given the early technological limitations on the shaft speed of the engine, the compressor needed to have a very large diameter to produce the power required. A further disadvantage was that the air flow had to be "bent" to flow rearwards through the combustion section and to the turbine and tailpipe.

Austrian Anselm Franz of Junkers' engine division (Junkers Motoren or Jumo) addressed these problems with the introduction of the axial-flow compressor. Essentially, this is a turbine in reverse. Air coming in the front of the engine is blown towards the rear of the engine by a fan stage (convergent ducts), where it is crushed against a set of non-rotating blades called stators (divergent ducts). The process is nowhere near as powerful as the centrifugal compressor, so a number of these pairs of fans and stators are placed in series to get the needed compression. Even with all the added complexity, the resulting engine is much smaller in diameter and thus, more aerodynamic. Jumo was assigned the next engine number, 4, and the result was the Jumo 004 engine. After many lesser technical difficulties were solved, mass production of this engine started in 1944 as a powerplant for the world's first jet-fighter aircraft, the Messerschmitt Me 262 (and later the worlds first jet-bomber aircraft, the Arado Ar 234). Because Hitler insisted the Me 262 be designated a bomber, this delay caused the fighter version to arrive too late to decisively impact Germany's position in World War II. Nonetheless, it will be remembered as the first use of jet engines in service. Following the end of the war the German jet aircraft and jet engines were extensively studied by the victorious allies and contributed to work on early Soviet and US jet fighters. The legacy of the axial-flow engine is seen in the fact that practically all jet engines on fixed wing aircraft have had some inspiration from this design.


Centrifugal-flow engines have improved since their introduction. With improvements in bearing technology, the shaft speed of the engine was increased, greatly reducing the diameter of the centrifugal compressor. The short engine length remains an advantage of this design, particularly for use in helicopters. Also, its engine components are robust; axial-flow compressors are more liable to foreign object damage.

British engines also were licensed widely in the US (see Tizard Mission). Their most famous design, the Nene would also power the USSR's jet aircraft after a technology exchange. American designs would not come fully into their own until the 1960s.

Engine cooling fans

Cooling fans are mechanical devices that removes the hot air and other gases, which is harmful with regards to the safety of the engine unit. These gases and hot air can be discomforting for the people sitting inside the vehicle.

These fans can be categorized in three ways.
1)Fans deliver large amounts of air or gas at low pressure,
2)blowers have high rates of delivery at medium pressure, and
3)compressors deliver at high pressure.

The cooling fan has to be controlled so that it allows the engine to maintain a constant temperature.

Almost all the front-wheel driven cars and vehicles have the electric cooling fans installed in them as their engine is usually mounted transversely. The fans are controlled by a thermostatic switch or by engine computer, and they turn on when the temperature of the coolant goes above a set point. They turn back off when the temperature drops below that point. Usually you find the automatics in more sophisticated cars.

Cars that are rear wheel driven have engines that are usually longitudinally placed and have these engine-driven cooling fans. These fans have a switch that is controlled with the surrounding temperature and is called as a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator. This special viscous clutch is much like the viscous coupling sometimes found in all-wheel drive cars. These types of latest engine cooling fans can be retrieved by placing special orders.

Some designers have applied a semi-analytic and semi empirical formula which is specifically developed for predicting noise radiation from engine cooling fan assemblies. These engine cooling fans significantly reduce the noise that is caused by the engine.

Radiator fans

By: Darren Dun

Do you know the importance of radiator fans? Well, to start with, can you imagine yourself in a room with a temperature of over 35-degree cc and with no cooling fans in the room to drive out the heat away? How would you feel sitting there all the while and perspiring! Definitely, your energy levels will go down and you will start to feel more restless. A cooling fan can indeed pump up the atmosphere by driving away the hot air of the room and make you feel more relaxed. The way our body behaves when subjected to extreme heat so also our vehicles require an engine-cooling fan to protect the engine of the car.

The automotive engine of the car produces a large amount of heat that can be severely damaging for the engine and its components. The engine if exposed o this amount of continuous heat can wear out and its life is decreased. The extreme heat generated by the vehicle can just burn of your engine, which will ultimately result in the breakdown of the car. As we, all know that an engine is the most important part of any vehicle. No vehicle can do without a suitable fitting engine as a result; it becomes very much important that we take special measures to protect the engine of our car or vehicle. Thus, the radiator fans come into picture.

Engine radiator fans transfer the excess amount of heat that is produced by the car and thus protects the parts from being burnt and wearing out before time. Almost all the radiator fans have four to six blades, which depend upon the size of the vehicle. The radiator fans work rapidly to provide sufficient airflow to your engine and to keep it cool. Usually the radiator fan is placed in between the engine and the radiator so that the heat gets the least traveled path.

Today almost every application requires radiators fans. These engine-cooling fans are used in various applications besides the vehicles, like street rods, passenger cars, trucks, racecar water radiators, oil coolers and differential coolers.

While looking for radiator fans it s important to check out the specifications of your car before making the purchase.

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Darren is an article writer currently writng for www.the-fan-man.com Find more information about the subject at www.the-fan-man.com