Potential causes Dieseling

An automobile engine that is dieseling will typically sputter then gradually stop rather than continue running as if the engine was not switched off at all — the latter would usually indicate an electrical fault.


Potential causes

This condition can occur for a multitude of reasons:

* Built-up carbon in the ignition chamber can glow red after the engine is off, providing a mechanism for sparking unburnt fuel. Such a thing can happen when the engine runs very rich, depositing unspent fuel and particles on the pistons and valves. Similarly, non-smooth metal regions within the piston chamber can cause this same problem, since they can glow red. It has also been suggested that an improperly rated sparkplug can retain heat and cause the same problem.

* A carburetor that does not close entirely can contribute to running once the engine is off, since the extra fuel and oxygen mixture can combust easily in the warm piston chamber. Similarly, hot vaporized oil gases from the engine crankcase can provide ample fuel for dieseling.

* Incorrect timing.

* An engine that runs too hot or too lean may produce an environment conducive to allowing unspent fuel to combust.

* An idle speed that is too fast can leave the engine with too much angular momentum upon shutdown, raising the chances that the engine can turnover and combust more fuel and lock itself into a cycle of continuous running.


Potential fixes

Items similar to carburetor cleaners and carbon cleaners have been suggested as partial remedies for attempting to clean the piston chambers and valves of engines that run too rich.

For those engines that have sharp metallic edges, it has been noted that poorly milled heads and blocks can contribute to this problem, so having the rough spots smoothed may help.

For those engines that run too hot or too lean, verify that all mechanisms in place to cool the engine properly function as they should. Replace the thermostat if necessary. Clean the radiator. Verify that all auxiliary fans engage at their proper temperatures, and ensure that the thermostatic sensors on belt driven fans engage as necessary.

In the case that there is too much angular momentum, lower the idle speed if possible.

Exhaust gas recirculation

Exhaust gas recirculation (EGR) is a NOx (nitrogen oxide and nitrogen dioxide) reduction technique used in most gasoline and diesel engines.

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with inert gas, lowering the adiabatic flame temperature and (in diesel engines) reducing the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix lowering the peak combustion temperature. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures.


EGR in Spark-Ignited (SI) Engines

In a typical automotive SI engine, 5 to 15 percent of the exhaust gas is routed back to the intake as EGR (thus comprising 5 to 15 percent of the mixture entering the cylinders). The maximum quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in an SI engine can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. Contrary to popular belief, a properly operating EGR actually increases the efficiency of gasoline engines via several mechanisms:

* Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.

* Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.

* Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC, rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is relatively minor compared to the first two.

It also decreases the efficiency of gasoline engines via a few more mechanisms

* Reduced intake charge density. EGR tends to heat the intake charge. This means a bigger piston or stroke must be used to induct the same amount of fuel and air mixture. This results in a bigger and heavier engine.

* Reduced specific heat ratio. A lean intake charge has a higher specific heat ratio than an EGR mixture. A reduction of specific heat ratio reduces the amount of energy that can be extracted by the piston.

EGR is typically not employed at high loads because it would reduce peak power output, and it is not employed at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.


EGR in Diesel Engines

In modern diesel engines, the EGR gas is cooled through a heat exchanger to allow the introduction of a greater mass of recirculated gas. Unlike SI engines, diesels are not limited by the need for a contiguous flamefront; furthermore, since diesels always operate with excess air, they benefit from EGR rates as high as 50% (at idle, where there is otherwise a very large amount of excess air) in controlling NOx emissions.

Since diesel engines are unthrottled, EGR does not lower throttling losses in the way that it does for SI engines (see above). However, exhaust gas (largely carbon dioxide and water vapor) has a higher specific heat than air, and so it still serves to lower peak combustion temperatures; this aids the diesel engine's efficiency by reduced heat rejection and dissociation. There are trade offs however. Adding EGR to a diesel reduces the specific heat ratio of the combustion gases in the power stroke. This reduces the amount of power that can be extracted by the piston. EGR also tends to reduce the amount of fuel burned in the power stroke. This is evident by the increase in particulate emissions that corresponds to an increase in EGR. Particulate matter (mainly carbon) that is not burned in the power stroke is wasted energy. Stricter regulations on particulate matter(PM) call for further emission controls to be introduced to compensate for the PM emissions introduced by EGR. The most common is particulate filters in the exhaust system that result in reduce fuel efficiency. Since EGR increases the amount of PM that must be dealt with and reduces the exhaust gas temperatures and available oxygen these filters need to function properly to burn off soot, automakers have had to consider injecting fuel and air directly into the exhaust system to keep these filters from plugging up.


Implementation of EGR

Recirculation is usually achieved by piping a route from the exhaust manifold to the inlet manifold, which is called external EGR. A control valve (EGR Valve) within the circuit regulates and times the gas flow. Some engine designs perform EGR by trapping exhaust gas within the cylinder by not fully expelling it during the exhaust stroke, which is called internal EGR. A form of internal EGR is used in the rotary Atkinson cycle engine.

EGR can also be used by using a variable geometry turbocharger (VGT) which uses variable inlet guide vanes to build sufficient backpressure in the exhaust manifold. For EGR to flow, a pressure difference is required across the intake and exhaust manifold and this is created by the VGT.

Other methods that have been experimented with are using a throttle in a turbocharged diesel engine to decrease the intake pressure to initiate EGR flow.

Early EGR systems were relatively unsophisticated, utilizing manifold vacuum as the only input to an on/off EGR valve; reduced performance and/or drivability were common side-effects. However, modern systems utilizing electronic engine control computers, multiple control inputs, and servo-driven EGR valves typically improve performance/efficiency with no impact on drivability. In the past, a meaningful fraction of car owners disconnected their EGR systems. Some still do either because they believe EGR reduces power output, causes a build-up in the intake manifold in diesel engines, or because they feel the environmental intentions of EGR are misguided. Disconnecting an EGR system is usually as simple as unplugging an electrically operated valve or inserting a ball bearing into the vacuum line in a vacuum-operated EGR valve. In all cases, the EGR system will need to be operating normally in order to pass emissions tests.

Diesel Performance

If you were to modify a gas engine for performance, you would be required to install a different camshaft, bore out the cylinders to increase displacement, install high compression pistons and heads, increase fuel intake capability by installing a larger carburetor or injection system, adding a turbo charger or supercharger, adding a chip, and enlarging the exhaust system.

But then you are still restricted by emission control systems. On the other hand, diesel trucks and cars are mostly turbo charged, and they already run at a higher compression ratio. Whereas on the gas vehicles you would have to make those changes. If you were to make those changes to a gas engine you would truly have a ground pounding beast, but would lose every day drive ability.

The Diesels on the other hand are nice to drive around even with considerable modification. With a cold air intake, a chip, more efficient injectors, and a more open exhaust system, the diesels are still a nice ride, but when you really give it the gas, all heck breaks loose. There is enormous power without reducing drive ability.

Because of the nature of diesel engines they are designed from the factory to withstand much higher compression ratios than a gas engine. The diesel fuel combusts when it is compressed to a certain point whether or not there is optimum air. By simply shooting more fuel into the combustion chamber you can make more power. When you then improve the air ratio & timing of the fuel - you can make dramatic power and also improve engine efficiency. Gasoline
requires a spark to ignite it & must have the appropriate mixture of air to burn properly. There is also a lot more energy in a given amount of diesel fuel than in an equal amount of gasoline.

I will now break down the most popular modifications and explain their benefits.

1. A cold air intake is sealed away from the hot engine air, and is
located where it can take in more air. Cold air intakes are equipped with a filter that can take in up to 300% more air. Cold air takes up less space. So there can be more air, more air helps to burn all the fuel, thus giving more power and better fuel economy.

2. Chips make alterations to how the fuel is delivered to the engine, making it more efficient and more powerful.

3. A bigger exhaust or a mandrel bent exhaust (keeps the tube round, and the size constant) improves exhaust flow. Getting exhaust away from the engine is just as important in combustion as getting air into the engine. There are exhausts now that will even vacuum exhaust away from the engine, making it so that the engine doesn’t have to do that work.

All of these modifications add to the fuel economy of the diesel engine, and will over time actually pay for themselves in gas savings, and will continue for years after they are paid for to keep your money in your pocket. Diesels are the wave of the future and more and more economy vehicles are being produced in diesel versions because they are capable of so much better economy.

vegetable oil for fuel history

The first known use of vegetable oil as fuel for a diesel engine was a demonstration of an engine built by the Otto company and designed to burn mineral oil, which was run off of pure peanut oil at the 1900 World's Fair. When Rudolf Diesel invented the diesel engine, he designed it to run on peanut oil but it was soon discovered that it would operate on cheaper petroleum oil. In a 1912 presentation to the British Institute of Mechanical Engineers, he cited a number of efforts in this area and remarked, "The fact that fat oils from vegetable sources can be used may seem insignificant today, but such oils may perhaps become in course of time of the same importance as some natural mineral oils and the tar products are now."

Periodic petroleum shortages spurred research into vegetable oil as a diesel substitute during the 30s and 40s, and again in the 70s and early 80s when straight vegetable oil enjoyed its highest level of scientific interest. The 1970s also saw the formation of the first commercial enterprise to allow consumers to run straight vegetable oil in their automobiles, Elsbett of Germany. In the 1990s Bougainville conflict, islanders cut off from oil supplies due to a blockade used coconut oil to fuel their vehicles.

Academic research into straight vegetable oil fell off sharply in the 80s with falling petroleum prices and greater interest in biodiesel as an option that did not require extensive vehicle modifications.

Dieseling...Curing The After Running.

AFTER one, or both, of two things, causes RUN OR DIESELING: too hot and too fast. Something's hot, too hot, inside a combustion chamber(s) causing it to ignite by itself. Usually it's because of too lean a condition, sometimes at idle. Try richening the idle mixture screws (counter clockwise) a tad and setting the timing to specs. Also lower the idle speed a little. Having the throttle closed more helps it kill easier.

It could also be just the opposite, too rich a mixture has caused carbon build up in the chambers, and a hot piece of carbon in a combustion chamber is the ignition source. In that case, lean it out, lower the idle a tad, and put a can of good carbon cleaner in the gas tank, such as GM's Carbon-X, or Chevron's Techron. Even though the can of "stuff" says you can pour it down the carburetor, it's better to let it burn off slowly. Even if your neighbor says to pour water down the carb, don't. Cold water (or chemicals) makes valve stems look like pretzels, and the steam washes the oil off the rings, not a good thing to do. And then there's always the possibility of causing a chuck of carbon breaking off and getting stuck where it does lots of damage.

Next fill gas tank with premium fuel, use name brand gas, not independents where you don't know what you're getting. Don't use gasohol or gasoline with high alcohol content.

If after doing the above, it's still a problem, add an idle solenoid. It's powered by ignition electrics. When you shut off the ignition, the throttle closes more, killing it. Lots of Jeepsters had them but since people didn't understand how they work they tossed them.

To adjust the solenoid, disconnect the wire to it, adjust for the slowest idle possible, but do not let the throttle plates close all the way (this prevents them from wearing the ventures.) Connect the wire; adjust the position of the solenoid or the plunger for best curb idle with the plunger extended. If you no longer have the solenoid or bracket, visit a junkyard. Lots of 60's and 70's cars used them; likely donors are GM's.

Sometimes a dieseling condition actually makes the engine run backwards a moment, pumping oil OUT of things, not good. I've seen where people walked away from their cars letting it "run on." When they got back it had melted internal parts.

What causes dieseling

The most common cause of that is the failure of the anti dieseling mechanism, sometimes an "anti dieseling solenoid", found on most late model carbureted cars. What is happening is that the throttle is remaining partially open when the engine is shut down, which gives the hot engine sufficient fuel to run without a spark from the spark plugs. Most hot engines have sufficient carbon build-up that remains glowing red hot and acts as an igniter for the fuel. The solution is to make sure that the throttle closes completely when you turn off the ignition switch. Check the throttle stop and make sure that the fast idle on the choke or the "bottom stop" isn't what is stopping the throttle from closing. It must be the anti-dieseling mechanism and that mechanism must be functional.

Some motors (Olds for example in 85) used an actual servo motor for this function. The motor drives a worm gear which advances or retracts the idle speed control rod depending on what the computer tells it to do. When it is in the "closed throttle" position and the key is killed it retracts completely to allow the throttle plate to close completely thus preventing the "dieseling" that so many cars are experiencing.

Diesel engine Glow Plug

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

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

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

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

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

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

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


Model engines

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

Hot bulb engine Differences from the Diesel Engine

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

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

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

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

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

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

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

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

Air start system

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

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

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

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

Air start system

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

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

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

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

diesel engine wet stacking

Wet stacking is a condition in diesel engines in which all the fuel is not burned and passes on into the exhaust side of the turbocharger and on into the exhaust system.

In generator sets, it is usually because the diesel is running at only a small percentage of its capacity. The accreditation body for hospitals JCAHO has been very concerned about this and has over the past few years dinged numerous hospitals for not running generator sets under at least 30% load as specified by the nameplate, or 50% of the normally connected emergency load, whichever is greater.

Some hospitals purchased large generators when they had the chance, anticipating expansion of the facility. As a result, some facilities fail to meet the percentage limits. Some of those that don't meet the load requirements have connected load banks to load up the generator to 80% of nameplate for a 4 hour annual run.

Wet stacking is detectable when there is a black ooze around exhaust pipe connections and around the turbocharger. Continuous black exhaust from the stack when under a constant load is also an indication that all the fuel is not being burned. Good preventive maintenance is critical for this type of generator application. There should be no surprises in the dark of night if the maintenance is being done correctly.

NFPA 110 speaks to the generator and wet stacking issues, and the 1997 JCAHO environment of care standards also address some change in the thinking on load bank testing.

A caution on load banks. If you choose to connect an external load bank to a required emergency power system, make sure that there is some automatic disconnect included that will take the load bank off-line if the generator is needed by the facility during the load bank run. If not, you may seriously overload the system if the emergency load from the hospital is added to the 80% load of the bank, causing a failure of the system when it is needed most.

Diesel cycle

The Diesel cycle is the combustion process of a type of internal combustion engine, in which the burning of the fuel is triggered by the heat generated in first compressing air in the piston cavity, into which is then injected the fuel - as opposed to it being ignited by a spark plug, as combustion is in the Otto cycle (four-stroke/petrol) engine. Diesel engines (heat engines utilizing the Diesel cycle) are used in automobiles, power generation, diesel-electric locomotives, and submarines.



Diesel cycle

The diesel cycle was introduced by Dr. Rudolph Diesel in 1897. In a Diesel cycle engine, heat is supplied (by the burning fuel) while maintaining the cylinder at a constant pressure.

The Diesel cycle generally refers to compression ignition power plants, called the Diesel engine. The engine can be two or four stroke and may draw in air by using the piston or with the aid of an engine-driven supercharger or exhaust gas-driven turbocharger. As the air is compressed it gets hot. When the piston reaches approximately "top dead center", the fuel is injected directly into the cylinder with a high-pressure fuel injector. The fuel ignites immediately; however, as diesel fuel has a higher molecular weight than gasoline, it vaporizes and burns more slowly. The piston is already moving down by the time the combustion starts, and combustion is usually not finished when the piston reaches "bottom dead center." Because of this incomplete combustion, diesel engines actually lose some of the potential energy of the fuel.

Diesel cycle engines are nevertheless more efficient than Otto cycle engines overall, but only when power needs to be scaled. Most land vehicles almost never use the maximum rated power of the engine. Unless the vehicle is at wide open throttle, when the pedal is 'floored', the engine is only producing a fraction of its rated power. Since diesel engines use the heating effect of compressing the air to ignite the fuel, a diesel engine can inject as little or as much fuel as the situation demands. It is important to note that Otto cycle engines can be more efficient than Diesel cycle engines, but only when the engine is running at or near its maximum power. This is dependent on the Otto cycle engine's compression ratio.



General information

The diesel engine has the lowest specific fuel consumption of any large internal combustion engine, 0.26 lb/hp.h (0.16 kg/kWh) for very large marine engines. In fact, two-stroke diesels with high pressure forced induction, particularly turbocharging, make up a large percentage of the very largest diesel engines.

In North America, diesel engines are primarily used in large trucks, where the low-stress, high-efficiency cycle leads to much longer engine life and lower operational costs. These advantages also make the diesel engine ideal for use in the heavy-haul railroad environment.



Other internal combustion engines without spark plugs

Many model airplanes use very simple "glow" and "diesel" engines. Glow engines use glow plugs. "Diesel" model airplane engines have variable compression ratios. Both types depend on special fuels (easily obtainable in such limited quantities) for their ignition timing.

Some 19th century or earlier experimental engines used external flames, exposed by valves, for ignition, but this becomes less attractive with increasing compression. (It was not until Nicolas Léonard Sadi Carnot that the thermodynamic value of compression was known.) An historical implication of this is that the diesel engine would eventually have been invented without the aid of electricity.

Fuel injection in diesel engines

Early fuel injection systems

The modern diesel engine is a combination of two inventors' creations. In all major aspects, it holds true to Diesel's original design, that of the fuel being ignited by compression at an extremely high pressure within the cylinder. However, nearly all present-day diesel engines use the so-called solid injection system invented by Herbert Akroyd Stuart, for his hot bulb engine (a compression-ignition engine that precedes the diesel engine and operates slightly differently). Solid injection is where the fuel is raised to extreme pressures by mechanical pumps and delivered to the combustion chamber by pressure-activated injectors in an almost solid-state jet. Diesel's original engine injected fuel with the assistance of compressed air, which atomised the fuel and forced it into the engine through a nozzle. This is called an air-blast injection. The size of the compressor needed to power such a system made early diesel engines very heavy and large for their power outputs, and the need to drive a compressor lowered power output even more. Early marine diesels often had smaller auxiliary engines whose sole purpose was to drive the compressors to supply air to the main engine's injector system. Such a system was too bulky and inefficient to be used for road-going automotive vehicles.

Solid injection systems are lighter, simpler, and allow for much higher RPMs, and so are universally used for automotive diesel engines. Air-blast systems provide very efficient combustion under low-speed, high-load conditions, especially when running on poor-quality fuels, so some large cathedral marine engines use this injection method. Air-blast injection also raises the fuel temperature during the injection process, so is sometimes known as hot-fuel injection. In contrast, solid injection is sometimes called cold-fuel injection.

Because the vast majority of diesel engines in service today use solid injection, the information below relates to that system.




Mechanical and electronic injection

Older engines make use of a mechanical fuel pump and valve assembly which is driven by the engine crankshaft, usually from the timing belt or chain. These engines use simple injectors which are basically very precise spring-loaded valves which will open and close at a specific fuel pressure. The pump assembly consists of a pump which pressurizes the fuel and a disc-shaped valve which rotates at half crankshaft speed. The valve has a single aperture to the pressurized fuel on one side, and one aperture for each injector on the other. As the engine turns, the valve discs will line up and deliver a burst of pressurized fuel to the injector at the cylinder about to enter its power stroke. The injector valve is forced open by the fuel pressure, and the diesel is injected until the valve rotates out of alignment and the fuel pressure to that injector is cut off. Engine speed is controlled by a third disc, which rotates only a few degrees and is controlled by the throttle lever. This disc alters the width of the aperture through which the fuel passes, and therefore how long the injectors are held open before the fuel supply is cut, which controls the amount of fuel injected.

Older diesel engines with mechanical injection pumps could be inadvertently run in reverse, albeit very inefficiently as witnessed by massive amounts of soot being ejected from the air intake. This was often a consequence of bump starting a vehicle using the wrong gear.

This contrasts with the more modern method of having a separate fuel pump (or set of pumps) which supplies fuel constantly at high pressure to each injector. Each injector then has a solenoid which is operated by an electronic control unit, which enables more accurate control of injector opening times that depend on other control conditions, such as engine speed and loading, resulting in better engine performance and fuel economy. This design is also mechanically simpler than the combined pump and valve design, making it generally more reliable, and less noisy, than its mechanical counterpart.

Both mechanical and electronic injection systems can be used in either direct or indirect injection configurations.




Indirect injection

An indirect injection diesel engine delivers fuel into a chamber off the combustion chamber, called a prechamber, where combustion begins and then spreads into the main combustion chamber, assisted by turbulence created in the chamber. This system allows smoother, quieter running, and because combustion is assisted by turbulence, injector pressures can be lower, which in the days of mechanical injection systems allowed high-speed running suitable for road vehicles (typically up to speed of around 4,000 rpm). The prechamber had the disadvantage of increasing heat loss to the engine's cooling system and restricting the combustion burn, which reduced the efficiency by between 5-10% in comparison to a direct injection engine, and nearly all require some form of cold-start device such as glow plugs. Indirect injection engines were used widely in small-capacity high-speed diesel engines in automotive, marine and construction uses from the 1950s, until direct-injection technology advanced in the 1980s. Indirect injection engines are cheaper to build and it is easier to produce smooth, quiet running vehicles with a simple mechanical system, so such engines are still often used in applications which carry less stringent emissions controls than road-going vehicles, such as small marine engines, generators, tractors, and pumps. With electronic injection systems, indirect injection engines are still used in some road-going vehicles, but most prefer the greater efficiency of direct injection.

During the development of the high-speed diesel engine in the 1930s, various engine manufacturers developed their own type of pre-combustion chamber. Some, such as Mercedes, had complex internal designs. Others, such as the Lanova pre-combustion chamber, used a mechanical system to adjust the shape of the chamber for starting and running conditions. However, the most commonly-used design turned out to be the 'Comet' series of swirl chambers developed by Harry Ricardo, using a two-piece spherical chamber with a narrow 'throat' to induce turbulence. Most European manufacturers of high-speed diesel engines used Comet-type chambers or developed their own versions (Mercedes stayed with their own design for many years), and this trend continues with current indirect-injection engines.



Direct injection

Modern diesel engines make use of one of the following direct injection methods:



Distributor pump direct injection

The first incarnations of direct injection diesels used a rotary pump much like indirect injection diesels; however the injectors were mounted in the top of the combustion chamber rather than in a separate pre-combustion chamber. Examples are vehicles such as the Ford Transit and the Austin Rover Maestro and Montego with their Perkins Prima engine. The problem with these vehicles was the harsh noise that they made and particulate (smoke) emissions. This is the reason that in the main this type of engine was limited to commercial vehicles— the notable exceptions being the Maestro, Montego and Fiat Croma passenger cars. Fuel consumption was about fifteen to twenty percent lower than indirect injection diesels, which for some buyers was enough to compensate for the extra noise.

One of the first small-capacity, mass-produced direct-injection engines that could be called refined was developed by the Rover Group.[citation needed] The '200Tdi' 2.5-litre 4-cylinder turbo diesel (of 111 horsepower) was used by Land Rover in their vehicles from 1989, and the engine used an aluminum cylinder head, Bosch two-stage injection and multi-phase glow plugs to produce a smooth-running and economical engine while still using mechanical fuel injection.

This type of engine was transformed by electronic control of the injection pump, pioneered by Volkswagen Audi group with the Audi 100 TDI introduced in 1989. The injection pressure was still only around 300 bar, but the injection timing, fuel quantity, exhaust gas recirculation and turbo boost were all electronically controlled. This gave much more precise control of these parameters which made refinement much more acceptable and emissions acceptably low. Fairly quickly the technology trickled down to more mass market vehicles such as the Mark 3 Golf TDI where it proved to be very popular. These cars were both more economical and more powerful than indirect injection competitors of their day.



Common rail direct injection

In older diesel engines, a distributor-type injection pump, regulated by the engine, supplies bursts of fuel to injectors which are simply nozzles through which the diesel is sprayed into the engine's combustion chamber.

In common rail systems, the distributor injection pump is eliminated. Instead an extremely high pressure pump stores a reservoir of fuel at high pressure - up to 1,800 bar (180 MPa, 26,000 psi) - in a "common rail", basically a tube which in turn branches off to computer-controlled injector valves, each of which contains a precision-machined nozzle and a plunger driven by a solenoid, or even by piezo-electric actuators, which are found on experimental diesel race car engines.

Most European automakers have common rail diesels in their model lineups, even for commercial vehicles. Some Japanese manufacturers, such as Toyota, Nissan and recently Honda, have also developed common rail diesel engines.

Different car makers refer to their common rail engines by different names, e.g. DaimlerChrysler's CDI, Ford Motor Company's TDCi (most of these engines are manufactured by PSA), Fiat Group's (Fiat, Alfa Romeo and Lancia) JTD, Renault's dCi, GM/Opel's CDTi (most of these engines are manufactured by Fiat, other by Isuzu), Hyundai's CRDi, Mitsubishi's DI-D, PSA Peugeot Citroën's HDi (Engines for commercial diesel vehicles are made by Ford Motor Company), Toyota's D-4D, and so on.



Unit direct injection

Unit direct injection also injects fuel directly into the cylinder of the engine. However, in this system the injector and the pump are combined into one unit positioned over each cylinder. Each cylinder thus has its own pump, feeding its own injector, which prevents pressure fluctuations and allows more consistent injection to be achieved. This type of injection system, also developed by Bosch, is used by Volkswagen AG in cars (where it is called a Pumpe-Düse-System - literally "pump-nozzle system") and by Mercedes Benz (PLD) and most major diesel engine manufacturers in large commercial engines (CAT, Cummins, Detroit Diesel). With recent advancements, the pump pressure has been raised to 2,050 bar (205 MPa), allowing injection parameters similar to common rail systems.



Hypodermic injection injury hazard

Because many diesel engine fuel injection systems operate at extremely high pressure, there is a risk of injury by hypodermic injection of fuel, if the fuel injector is removed from its seat and operated in open air.

How diesel engines work

When a gas is compressed, its temperature rises (see the combined gas law); a diesel engine uses this property to ignite the fuel. Air is drawn into the cylinder of a diesel engine and is compressed by the moving piston at a compression ratio as high as 25:1, much higher than needed for a spark-ignition engine. At the end of the piston stroke, diesel fuel is injected into the combustion chamber at high pressure through an atomising nozzle. The fuel ignites directly from contact with the air, the temperature of which reaches 700–900 °C (1300–1650 °F). The combustion causes the gas in the chamber to heat up rapidly, which increases its pressure, which in turn forces the piston outward. The connecting rod transmits this motion to the crankshaft, which delivers rotary power at its output end. Scavenging (pushing the exhausted gas-charge out of the cylinder and drawing in a fresh draught of air) of the engine is done either by ports or valves. To significantly increase the efficiency of a diesel engine, a turbocharger to compress the intake air is often used. Use of an aftercooler/intercooler to cool the intake air after compression by the turbocharger further improves efficiency.

In cold weather, diesel engines can be difficult to start because the cold metal of the cylinder block and head draw out the heat created in the cylinder during the compression stroke, thus preventing ignition. Most Diesel engines use small electric heaters called glow plugs inside the cylinder to warm the cylinders prior to starting. Some even use resistive grid heaters in the intake manifold to warm the inlet air until the engine reaches operating temperature. Engine block heaters (electric resistive heaters in the engine block) plugged into the utility grid are often used when an engine is shut down for extended periods (more than an hour) in cold weather to reduce startup time and engine wear. Diesel fuel is also prone to 'waxing' in cold weather. This is when the fuel begins to solidify into a crystaline state. The crystals build up in the fuel system (especially the fuel filters), eventually starving the engine of fuel. Low-output electric heaters in fuel tanks and around fuel lines are used to solve this problem. Also, most engines have a 'spill return' system, by which any excess fuel from the injector pump and injectors is returned to the fuel tank. Once the engine is warmed up, this warm fuel will prevent waxing in the tank. Fuel technology has improved in recent years, with special additives preventing waxing in all but the coldest climates.

A vital component of older diesel engine systems is the governor, which limits the speed of the engine by controlling the rate of fuel delivery. Unlike in petrol (gasoline) engines, incoming air is not throttled and an engine without a governor can overspeed. Older injection systems were driven by a gear system from the engine and thus supplied fuel in proportion with engine speed. Modern, electronically controlled engines apply controls similar to those of petrol engines and limit the maximum RPM through an electronic control module (ECM) or electronic control unit (ECU)—the engine-mounted computer. The ECM/ECU receives an engine speed signal from a sensor and controls the amount of fuel and (start of injection) timing through electric or hydraulic actuators.

Controlling the timing of the start of injection of fuel into the cylinder is a key to minimizing emissions, and maximizing fuel economy (efficiency), of the engine. The timing is usually measured in units of crank angle of the piston before Top Dead Center (TDC). For example, if the ECM/ECU initiates fuel injection when the piston is 10 degrees before TDC, the start of injection, or timing, is said to be 10 deg BTDC. Optimal timing will depend on the engine design as well as its speed and load.

Advancing the start of injection (injecting before the piston reaches TDC) results in higher in-cylinder pressure and temperature, and higher efficiency, but also results in higher emissions of oxides of nitrogen (NOx) because of the higher temperatures. At the other extreme, delayed start of injection causes incomplete combustion. This results in higher particulate matter (PM) and unburned hydrocarbon (HC) emissions and more smoke.

Diesel engine and history

The steam engine is a type of internal combustion engine. It is a compression ignition engine, in which the fuel ignites as it is injected into the engine. By contrast, in the gasoline engine the fuel is mixed first and then ignited by a spark plug. Also, diesels generally have high compression ratios, to enable compression ignition, whereas in gasoline-burning engines, compression ignition is undesirable.

The engine operates using the diesel cycle.

The engine is named after German engineer Rudolf Diesel, who invented it in 1892 based on the hot bulb engine and received the patent on February 23, 1893. Diesel intended the engine to use a variety of fuels including coal dust and peanut oil. He demonstrated it at the 1900 Exposition Universelle (World's Fair) using peanut oil.



Early history timeline

* 1862: Nicolaus Otto develops his coal gas engine, similar to a modern gasoline engine.

* 1891: Herbert Akroyd Stuart, of Bletchley perfects his oil engine, and leases rights to Hornsby of England to build engines. They build the first cold start, compression ignition engines.

* 1892: Hornsby engine No. 101 is built and installed in a waterworks. It is now in the MAN truck museum in Northern England.

* 1892: Rudolf Diesel develops his Carnot heat engine type motor which burnt powdered coal dust. He is employed by refrigeration genius Carl von Linde, then Munich iron manufacturer MAN AG, and later by the Sulzer engine company of Switzerland. He borrows ideas from them and leaves a legacy with all firms.

* 1892: John Froelich builds his first oil engine powered farm tractor.

* 1894: Witte, Reid, and Fairbanks start building oil engines with a variety of ignition systems.

* 1896: Hornsby builds diesel tractors and railway engines.

* 1897: Winton produces and drives the first US built gas automobile; he later builds diesel plants.

* 1897: Mirrlees, Watson & Yaryan build the first British diesel engine under license from Rudolf Diesel. This is now displayed in the Science Museum at South Kensington, London.

* 1898: Busch installs a Rudolf Diesel type engine in his brewery in St. Louis. It is the first in the United States. Rudolf Diesel perfects his compression start engine, patents, and licences it. This engine, pictured above, is in a German museum.

* 1899: Diesel licences his engine to builders Burmeister & Wain, Krupp, and Sulzer, who become famous builders.

* 1902: F. Rundlof invents the two-stroke crankcase, scavenged hot bulb engine.

* 1902: A company named Forest City [1] start manufacturing diesel generators.

* 1903: Ship Gjoa transits the ice-filled Northwest Passage, aided with a Dan kerosene engine.

* 1904: French build the first diesel submarine, the Z.

* 1908: Bolinder-Munktell starts building two stroke hot-bulb engines.

* 1912: First diesel ship MS Selandia is built. SS Fram, polar explorer Amundsen’s flagship, is converted to a AB Atlas diesel.

* 1913: Fairbanks Morse starts building its Y model semi-diesel engine. US Navy submarines use NELSECO units.

* 1914: German U-Boats are powered by MAN diesels. War service proves engine's reliability.

* 1920s: Fishing fleets convert to oil engines. Atlas-Imperial of Oakland, Union, and Lister diesels appear.

* 1924: First diesel trucks appear.

* 1928: Canadian National Railways employ a diesel shunter in their yards.

* 1930s: Clessie Cummins starts with Dutch diesel engines, and then builds his own into trucks and a Duesenberg luxury car at the Daytona speedway.

* 1930s: Caterpillar starts building diesels for their tractors.

* 1933: Citroën introduced the Rosalie, a passenger car with the world’s first commercially available diesel engine developed with Harry Ricardo.

* 1934: General Motors starts a GM diesel research facility. It builds diesel railroad engines—The Pioneer Zephyr—and goes on to found the General Motors Electro-Motive Division, which becomes important building engines for landing craft and tanks in the Second World War. GM then applies this knowledge to market control with its famous Green Leakers for buses and railroad engines.

* 1936: Mercedes-Benz builds the 260D diesel car. A.T.S.F inaugurates the diesel train Super Chief.

* 1936: Airship Hindenburg is powered by diesel engines.

Honda A engine

History

The Honda A-series engines succeeded the earlier EZ, ES, BS and ET engines in the Honda Accord and Prelude. Some of those engines were actually early A-series engines and parts between them may be cross-compatible. There were several variations, ranging from the 1.6 liter A16A to the 2.0 liter A20A. All A-series engines have iron blocks with single overhead camshaft aluminum heads and are the last iron blocked engine produced by Honda. They came in both carbed and fuel injected configurations.



Technology & Advancement

Although they don't have VTEC, the A-series engines were well-designed engines. Analysis of the head construction has showed that Honda was using valve geometry and technology several years ahead of their time. Also, the later model of the A20A3 & A20A4 benefitted from the addition of a dual-stage runner intake manifold design, 4-2-1 headers, and a more electronic form of the vacuum advanced distributor. The PGM-FI engines were equipped with partial OBD-0 engine computers.



Aftermarket

The aftermarket for the A-series engines (and the cars they came in) is all but dead. An A-equipped vehicle isn't for someone who wants bolt-ons from Wal-Mart or even your local import performance shop. Most upgrades and modifications to the A-series engines are of the DIY variety, with one of the more popular being a turbo set-up. Because of their closed-deck iron block design, they're especially well-suited for handling boost. It's just a pity that Honda didn't capitalize on that from the factory. And since a VTEC version of any of the A-series engines was never produced, swaps akin to an LS/VTEC or "mini-me" aren't doable because no VTEC head bolts to the A-series block.



A-Series Engines



A16A1

The A16A1 was a carburated 1.6 liter engine used in the 1982-1985 Honda Accords in North America and in some of the 1986-1989 Accords in the non-USDM market.

Specifications

* Carbeurated
* Displacement: 1596 cm³
* Bore: 80 mm
* Stroke: 79.5 mm
* Power:
o 88 hp @ 6000 rpm
o 91 ft/lb torque @ 3500 rpm



A18A

The A18A engine was the 1.8 liter engine found in the 1982-1985 Honda Accords as well as the 1984-1987 Honda Prelude in the US. Abroad, it was also available in the 1986-1989 Accords.

Specifications

* Carbeurated
* Displacement: 1829 cm³
* Bore:
* Stroke:
* Power:
o 110 hp @ 5800 rpm
o 112 ft/lbs @ 3500 rpm


A20A

The A20A is probably the most plentiful of all the Honda A-series engines. It was available in both carbeurated and PGM-FI versions. They were found in both Accords and Preludes throughout the 1980s.



A20A1 & A20A2

The A20A1 and A20A2 were the carbeurated versions of the A20A engines. It was available in the 1984-1987 Honda Preludes as well as the 1982-1989 Accord DX and LX. They are the same engine, the only difference between them being that the A20A2 has no emissions components, so it has a slightly higher power output (hp and tq numbers for A20A1 only).

Specifications

* Carbeurated
* Displacement: 1955 cm³
* Bore:
* Stroke:
* Power:
o 98 hp
o 109 ft/lb at 3500 rpm


A20A3 & A20A4

The A20A3 and A20A4 were the fuel injected versions of the A20A engines. They were run by Honda's PGM-FI system on a partial OBD-0 computer. Again, there is no real difference between the A20A3 and the A20A4 besides the A20A4 having a slightly higher power output because of not having emissions components (hp and tq numbers for A20A3 only). The A20A3 was offered in the 1984-1987 Honda Prelude 2.0Si, the 1985 and 1989 Honda Accord SE-i, and the 1986-1989 Honda Accord LX-i.

Specifications

* PGM-FI
* Displacement: 1956 cm³
* Bore:
* Stroke:
* Power:
o 1986-1987: 110 hp @ 5500 rpm & 114 ft/lb @ 4500 rpm
o 1988-1989: 120 hp @ 5500 rpm & 122 ft/lb @ 4000 rpm

Two-stroke diesel engines

A two-stroke cycle has also been used for some diesel engines. As the fuel is injected directly into the cylinder, the lubrication of the crankshaft must be independent in these engines. There is no mixing of lubricating oil into the fuel.

There are three patterns. Some modern designs differ from the gasoline two-stroke cycle in that they have intake and exhaust valves in the cylinder head, exactly like a four-stroke engine. In these engines, the two-stroke cycle is used to improve power-to-weight ratio and/or reduce the engine speed to increase reliability. This pattern, the Clark cycle, is common in truck, railroad locomotive and machinery engines.

Other engines have used the same ported arrangement as the gasoline two-stroke, although the charge air is generally delivered under pressure from a blower through ducting rather than through the crankcase. Examples are the Junkers Jumo 205 and Napier Deltic high-speed opposed piston engines.

A third pattern uses the induction method of the gasoline two-stroke, but with an exhaust valve in the cylinder head. Large marine diesels commonly use this arrangement. These engines commonly also use a crosshead bearing, which together with a sliding seal on the piston rod allows the air path to be separated from the crankshaft while still using the piston movement as an air pump.

The simpler stroke in the fully valved diesel two-stroke cycle is the compression stroke; both valves are closed, and the rising piston compresses the air, heating it. At the top of the stroke, diesel fuel is injected into the cylinder, where it ignites and burns. The hot, high pressure gases produced by the combustion push against the piston as it descends in the initial part of the second stroke, delivering power. At this point, both valves are still closed. When the piston nears the bottom of the stroke, the exhaust valve opens, and the exhaust gases, still under pressure, rush out. The intake valve then opens. Air under pressure rushes into the cylinder, blowing out the remainder of the exhaust gases. The exhaust valve closes at that point, and shortly after that, and at about bottom dead center, so does the intake valve.

If the crankcase is not used as an air pump, some other means of forced induction is required, and is often used for efficiency in any case. The intake air must be under pressure, since the engine does not have an induction stroke and cannot suck the air in by itself. A low-pressure supercharger (blower) is needed at minimum, but many are turbocharged. Crossley two-stroke diesels were equipped with "exhaust-pulse pressure-charging" whereby surplus air in the exhaust manifold was forced back into the cylinder by the exhaust-pulse from a neighbouring cylinder.

The diesel two-stroke generally lacks the inefficiency and pollution problems of the gasoline two-stroke, since no unburned fuel, only air, can get blown out of the exhaust valve before it closes. Also, there is no mixing of lubricant with the fuel.

Crude oil engine

The crude oil engine is a type of internal combustion engine similar to the hot bulb engine. A crude oil engine could be driven by all sorts of oils such as engine waste oil and vegetable oils. Anything could be used as fuel, even peanut oil and butter if it was necessary. Like hot bulb engines, crude oil engines were mostly used as stationary engines or in boats. They can run for a very long time, for instance at the world fair in Milano in 1907, a FRAM engine was started and it wasn't stopped until the exhibition was over one month later. A crude oil engine is a low RPM engine dimensioned for constant running and can last for a very long time if maintained properly.

It was later replaced by the diesel engine.