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Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. This article focuses on fuel injection in reciprocating piston and Wankel engine engines.
All compression-ignition engines (e.g. ), and many spark-ignition engines (i.e. petrol engines, such as Otto engine or Wankel engine), use fuel injection of one kind or another. Mass-produced diesel engines for passenger cars (such as the Mercedes-Benz OM 138) became available in the late 1930s and early 1940s, being the first fuel-injected engines for passenger car use. (2025). 9783709150160, Springer. ISBN 9783709150160 In passenger car petrol engines, fuel injection was introduced in the early 1950s and gradually gained prevalence until it had largely replaced by the early 1990s. The primary difference between carburetion and fuel injection is that fuel injection atomizer nozzle the fuel through a small nozzle under high pressure, while carburetion relies on suction created by intake air accelerated through a Venturi effect to draw fuel into the airstream.
The term fuel injection is vague and comprises various distinct systems with fundamentally different functional principles. The only thing all fuel injection systems have in common is the absence of carburetion.
There are two main functional principles of mixture formation systems for internal combustion engines: internal and external. A fuel injection system that uses external mixture formation is called a manifold injection system. There exist two types of manifold injection systems: multi-point (or port) and single-point (or throttle body) injection.
Internal mixture formation systems can be separated into several different varieties of direct and indirect injection, the most common being the Common rail, a variety of direct injection. The term electronic fuel injection refers to any fuel injection system controlled by an engine control unit.
Several early mechanical injection systems used relatively sophisticated helix-controlled injection pump(s) that both metered fuel and created injection pressure. Since the 1980s, electronics have been used to control the metering of fuel. More recent systems use an electronic engine control unit which meters the fuel and controls the ignition timing and various other engine functions.
Fuel injectors which also control the metering are called injection valves, while injectors that perform all three functions are called .
Fuel is injected directly into the combustion chamber either with a blast of airRüdiger Teichmann, Günter P. Merker (publisher) or hydraulically, with the former rendered obsolete in automotive engines in the early 20th century by the invention of the precombustion chamber.
Typically, hydraulic direct injection systems spray fuel into the air inside the cylinder or combustion chamber. Direct injection can be achieved with a conventional helix-controlled injection pump, unit injectors, or a sophisticated common-rail injection system. The last is the most common system in modern automotive engines.
The types of common-rail systems include air-guided injectionRichard van Basshuysen (ed.): Ottomotor mit Direkteinspritzung und Direkteinblasung: Ottokraftstoffe, Erdgas, Methan, Wasserstoff, 4th edition, Springer, Wiesbaden 2017, , p. 62 and spray-guided injection.
These systems use either a continuous injection or an intermittent injection design. In a continuous injection system, fuel flows at all times from the fuel injectors, but at a variable flow rate. The most common automotive continuous injection system is the multi-point Bosch K-Jetronic system, introduced in 1974 and used until the mid-1990s by various car manufacturers. Intermittent injection systems can be sequential, in which injection is timed to coincide with each cylinder's intake stroke; batched, in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke; simultaneous, in which fuel is injected at the same time to all the cylinders; or cylinder-individual, in which the engine control unit can adjust the injection for each cylinder individually.Konrad Reif (ed.): Ottomotor-Management, 4th edition, Springer, Wiesbaden 2014, , p. 107
Types of indirect injection used by diesel engines include:
In 1891, the British Herbert-Akroyd oil engine became the first engine to use a pressurised fuel injection system. This design, called a hot-bulb engine used a 'jerk pump' to dispense fuel oil at high pressure to an injector. Another development in early diesel engines was the pre-combustion chamber, which was invented in 1919 by Prosper l'Orange to avoid the drawbacks of air-blast injection systems. The pre-combustion chamber made it feasible to produce engines in size suitable for automobiles and MAN Truck & Bus presented the first direct-injected diesel engine for trucks in 1924.von Fersen (ed.), p. 130 Higher pressure diesel injection pumps were introduced by Bosch in 1927.
In 1898, German company Deutz AG started producing four-stroke petrol stationary engines with manifold injection. The 1906 Antoinette 8V aircraft engine (the world's first V8 engine) was another early four-stroke engine that used manifold injection. The first petrol engine with direct-injection was a two-stroke aircraft engine designed by Otto Mader in 1916.Richard van Basshuysen (ed.): Ottomotor mit Direkteinspritzung und Direkteinblasung: Ottokraftstoffe, Erdgas, Methan, Wasserstoff, 4th edition, Springer, Wiesbaden 2017, , p. 7 Another early spark-ignition engine to use direct-injection was the 1925 Hesselman engine, designed by Swedish engineer Jonas Hesselman. This engine could run on a variety of fuels (such as oil, kerosene, petrol or diesel oil)Richard van Basshuysen (ed.): Ottomotor mit Direkteinspritzung und Direkteinblasung: Ottokraftstoffe, Erdgas, Methan, Wasserstoff, 4th edition, Springer, Wiesbaden 2017, , pp. 17–18 and used a stratified charge principle whereby fuel is injected towards the end of the compression stroke, then ignited with a spark plug.
The Cummins Model H diesel truck engine was introduced in America in 1933. In 1936, the Mercedes-Benz OM 138 diesel engine (using a precombustion chamber) became one of the first fuel-injected engines used in a mass-production passenger car.Olaf von Fersen (ed.): Ein Jahrhundert Automobiltechnik. Personenwagen, VDI-Verlag, Düsseldorf 1986, . p. 274
The first mass-produced petrol direct-injection system was developed by Bosch and initially used in small automotive two-stroke petrol engines. Introduced in the 1950 Goliath GP700 small saloon, it was also added to the Gutbrod Superior engine in 1952. This mechanically-controlled system was essentially a specially lubricated high-pressure diesel direct-injection pump of the type that is governed by the vacuum behind an intake throttle valve.Richard van Basshuysen (ed.): Ottomotor mit Direkteinspritzung und Direkteinblasung: Ottokraftstoffe, Erdgas, Methan, Wasserstoff, 4th edition, Springer, Wiesbaden 2017, , p. 19 A Bosch mechanical direct-injection system was also used in the straight-eight used in the 1954 Mercedes-Benz W196 Formula One racing car. The first four-stroke direct-injection petrol engine for a passenger car was released the following year, in the Mercedes-Benz 300SL sports car.Richard van Basshuysen (ed.): Ottomotor mit Direkteinspritzung und Direkteinblasung: Ottokraftstoffe, Erdgas, Methan, Wasserstoff, 4th edition, Springer, Wiesbaden 2017, , p. 20 However the engine suffered lubrication problems due to petrol diluting the engine oil, and subsequent Mercedes-Benz engines switched to a manifold injection design. Likewise, most petrol injection systems prior to the 2000s used the less-expensive manifold injection design.
Up until this time, the fuel injection systems had used a mechanical control system. In 1957, the American Bendix Electrojector system was introduced, which used analogue electronics for the control system. The Electrojector was intended to be available for the Rambler Rebel mid-size car, however reliability problems meant that the fuel injection option was not offered. In 1958, the Chrysler 300D, DeSoto Adventurer, Dodge D-500 and Plymouth Fury offered the Electrojector system, becoming the first cars known to use an electronic fuel injection (EFI) system.
The Electrojector patents were subsequently sold to Bosch, who developed the Electrojector into the Bosch D-Jetronic. The D-Jetronic was produced from 1967-1976 and first used on the VW 1600TL/E. The system was a speed/density system, using engine speed and intake manifold air density to calculate the amount of fuel to be injected. In 1974, Bosch introduced the K-Jetronic system, which used a continuous flow of fuel from the injectors (rather than the pulsed flow of the D-Jetronic system). K-Jetronic was a mechanical injection system, using a plunger actuated by the intake manifold pressure which then controlled the fuel flow to the injectors.Olaf von Fersen (ed.): Ein Jahrhundert Automobiltechnik. Personenwagen, VDI-Verlag, Düsseldorf 1986, . p. 256
Also in 1974, Bosch introduced the L-Jetronic system, a pulsed flow system which used an air flow meter to calculate the amount of fuel required. L-Jetronic was widely adopted on European cars during the 1970s and 1980s. As a system that uses electronically-controlled fuel injectors which open and close to control the amount of fuel entering the engine, the L-Jetronic system uses the same basic principles as modern electronic fuel injection (EFI) systems.
The aforementioned injection systems for petrol passenger car enginesexcept for the 1954–1959 Mercedes-Benz 300 SLall used manifold injection (i.e. the injectors located at the intake ports or throttle body, instead of inside the combustion chamber). This began to change when the first mass-produced petrol direct injection system for passenger cars was a common rail system introduced in the 1997 Mitsubishi 6G74 V6 engine.Richard van Basshuysen (ed.): Ottomotor mit Direkteinspritzung und Direkteinblasung: Ottokraftstoffe, Erdgas, Methan, Wasserstoff, 4th edition, Springer, Wiesbaden 2017, , p. 138 Alt URL The first common-rail system for a passenger car diesel engine was the Fiat Multijet straight-four engine,Günter P. Merker, Rüdiger Teichmann (ed.): Grundlagen Verbrennungsmotoren – Funktionsweise · Simulation · Messtechnik, 7th edition, Springer, Wiesbaden 2014, , p. 179 introduced in the 1999 Alfa Romeo 156 1.9 JTD model. Since the 2010s, many petrol engines have switched to direct-injection (sometimes in combination with separate manifold injectors for each cylinder). Similarly, many modern diesel engines use a common-rail design.
Stratified charge injection was used in several petrol engines in the early 2000s, such as the introduced in 2000. However, the stratified charge systems were largely no longer in use by the late 2010s, due to increased exhaust emissions of NOx gasses and particulates, along with the increased cost and complexity of the systems.
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