Fuel injection

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Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, having replaced carburetors during the 1980s and 1990s. A variety of injection systems have existed since the earliest usage of the internal combustion engine.





The modern digital electronic fuel injection system is more capable at optimizing these competing objectives consistently than earlier fuel delivery systems (such as carburetors). Carburetors have the potential to atomize fuel better (see Pogue and Allen Caggiano patents).[dubious ]


Driver benefits

Operational benefits to the driver of a fuel-injected car include smoother and more dependable engine response during quick throttle transitions, easier and more dependable engine starting, better operation at extremely high or low ambient temperatures, smoother engine idle and running, increased maintenance intervals, and increased fuel efficiency. On a more basic level, fuel injection does away with the choke, which on carburetor-equipped vehicles must be operated when starting the engine from cold and then adjusted as the engine warms up.

Environmental benefits

Fuel injection generally increases engine fuel efficiency. With the improved cylinder-to-cylinder fuel distribution of multi-point fuel injection, less fuel is needed for the same power output (when cylinder-to-cylinder distribution varies significantly, some cylinders receive excess fuel as a side effect of ensuring that all cylinders receive sufficient fuel).


History and development

Herbert Akroyd Stuart developed the first device with a design similar to modern fuel injection[citation needed], using a 'jerk pump' to meter out fuel oil at high pressure to an injector. This system was used on the hot bulb engine and was adapted and improved by Bosch and Clessie Cummins for use on diesel engines (Rudolf Diesel's original system employed a cumbersome 'air-blast' system using highly compressed air[citation needed]). Fuel injection was in widespread commercial use in diesel engines by the mid-1920s.

An early use of indirect gasoline injection dates back to 1902, when French aviation engineer Leon Levavasseur pioneered it on his Antoinette 8V aircraft powerplant.[1]

Another early use of gasoline direct injection (i.e. injection of gasoline, also known as petrol) was on the Hesselman engine invented by Swedish engineer Jonas Hesselman in 1925.[2][3] Hesselman engines use the ultra lean burn principle; fuel is injected toward the end of the compression stroke, then ignited with a spark plug. They are often started on gasoline and then switched to diesel or kerosene.[4]


Alfa Romeo tested one of the very first electronic injection systems (Caproni-Fuscaldo) in Alfa Romeo 6C2500 with "Ala spessa" body in 1940 Mille Miglia. The engine had six electrically operated injectors and were fed by a semi-high-pressure circulating fuel pump system.[5]

Development in diesel engines

All diesel engines (with the exception of some tractors and scale model engines have fuel injected into the combustion chamber. See diesel engines.

Development in gasoline/petrol engines

Mechanical injection


The invention of mechanical injection for gasoline-fueled aviation engines was by the French inventor of the V8 engine configuration, Leon Levavasseur in 1902.[6] Levavasseur designed the original Antoinette firm's series of V-form aero engines, starting with the Antoinette 8V to be used by the aircraft the Antoinette firm built that Levavasseur also designed, flown from 1906 to the firm's demise in 1910, with the world's first V16 engine, using Levavasseur's direct injection and producing some 100 hp, flying an Antoinette VII monoplane in 1907.

The first post-World War I example of direct gasoline injection was on the Hesselman engine invented by Swedish engineer Jonas Hesselman in 1925.[7][8] Hesselman engines used the ultra lean burn principle and injected the fuel in the end of the compression stroke and then ignited it with a spark plug, it was often started on gasoline and then switched over to run on diesel or kerosene. The Hesselman engine was a low compression design constructed to run on heavy fuel oils.

Direct gasoline injection was applied during the Second World War to almost all higher-output production aircraft powerplants made in Germany (the widely used BMW 801 radial, and the popular inverted inline V12 Daimler-Benz DB 601, DB 603 and DB 605, along with the similar Junkers Jumo 210G, Jumo 211 and Jumo 213, starting as early as 1937 for both the Jumo 210G and DB 601), the Soviet Union (Shvetsov ASh-82FN radial, 1943, Chemical Automatics Design Bureau - KB Khimavtomatika) and the USA (Wright R-3350 Duplex Cyclone radial, 1944).

Immediately following the war, hot rodder Stuart Hilborn started to offer mechanical injection for race cars, salt cars, and midgets,[9] well-known and easily distinguishable because of their prominent velocity stacks projecting upwards from the engine they were used on.

The first automotive direct injection system used to run on gasoline was developed by Bosch, and was introduced by Goliath for their Goliath GP700 automobile, and Gutbrod in 1952. This was basically a high-pressure diesel direct-injection pump with an intake throttle valve set up. (Diesels only change the amount of fuel injected to vary output; there is no throttle.) This system used a normal gasoline fuel pump, to provide fuel to a mechanically driven injection pump, which had separate plungers per injector to deliver a very high injection pressure directly into the combustion chamber. The 1954 Mercedes-Benz W196 Formula 1 racing car engine used Bosch direct injection derived from wartime aero engines. Following this racetrack success, the 1955 Mercedes-Benz 300SL, the first production sports car to use fuel injection, used direct injection. The same engine was used in the Mercedes-Benz 300SLR famously driven by Stirling Moss to victory in the 1955 Mille Miglia. The Bosch fuel injectors were placed into the bores on the cylinder wall used by the spark plugs in other Mercedes-Benz six-cylinder engines (the spark plugs were relocated to the cylinder head). Later, more mainstream applications of fuel injection favored the less-expensive indirect injection methods.





Electronic injection

The first commercial electronic fuel injection (EFI) system was Electrojector, developed by the Bendix Corporation and was offered by American Motors Corporation (AMC) in 1957.[12][13] The Rambler Rebel, showcased AMC's new 327 cu in (5.4 L) engine. The Electrojector was an option and rated at 288 bhp (214.8 kW).[14] The EFI produced peak torque 500 rpm lower than the equivalent carburetored engine[10] The Rebel Owners Manual described the design and operation of the new system.[15] (due to cooler, therefore denser, intake air[citation needed]). The cost of the EFI option was US$395 and it was available on 15 June 1957.[16] Electrojector's teething problems meant only pre-production cars were so equipped: thus, very few cars so equipped were ever sold[17] and none were made available to the public.[18] The EFI system in the Rambler ran fine in warm weather, but suffered hard starting in cooler temperatures.[16]

Chrysler offered Electrojector on the 1958 Chrysler 300D, DeSoto Adventurer, Dodge D-500 and Plymouth Fury, arguably the first series-production cars equipped with an EFI system. It was jointly engineered by Chrysler and Bendix. The early electronic components were not equal to the rigors of underhood service, however, and were too slow to keep up with the demands of "on the fly" engine control. Most of the 35 vehicles originally so equipped were field-retrofitted with 4-barrel carburetors. The Electrojector patents were subsequently sold to Bosch.






The Cadillac Seville was introduced in 1975 with an EFI system made by Bendix and modelled very closely on Bosch's D-Jetronic. L-Jetronic first appeared on the 1974 Porsche 914, and uses a mechanical airflow meter (L for Luft, German for "air") that produces a signal that is proportional to "air volume". This approach required additional sensors to measure the atmospheric pressure and temperature, to ultimately calculate "air mass". L-Jetronic was widely adopted on European cars of that period, and a few Japanese models a short time later.

In 1980, Motorola (now Freescale) introduced the first electronic engine control unit, the EEC-III.[21] Its integrated control of engine functions (such as fuel injection and spark timing) is now the standard approach for fuel injection systems. The Motorola technology was installed in Ford North American products.

Supersession of carburetors


The open loop fuel injection systems had already improved cylinder-to-cylinder fuel distribution and engine operation over a wide temperature range, but did not offer further scope to sufficient control fuel/air mixtures, in order to further reduce exhaust emissions. Later Closed loop fuel injection systems improved the air/fuel mixture control with an exhaust gas oxygen sensor and began incorporating a catalytic converter to further reduce exhaust emissions.


Many motorcycles still utilize carburetored engines, though all current high-performance designs have switched to EFI.

NASCAR finally replaced carburetors with fuel-injection, starting at the beginning of the 2012 NASCAR Sprint Cup Series season.[22][23][24]

System components

System overview


Determining how much fuel to supply



Supplying the fuel to the engine


EFI gasoline engine components

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


Engine control unit

Main article: engine control unit


Fuel injector


Target air/fuel ratios


See air-fuel ratio, stoichiometry, and combustion.

Various injection schemes

Single-point injection

Single-point injection uses a single injector at the throttle body (the same location as was used by carburetors).

It was introduced in the 1940s in large aircraft engines (then called the pressure carburetor) and in the 1980s in the automotive world (called Throttle-body Injection by General Motors, Central Fuel Injection by Ford, PGM-CARB by Honda, and EGI by Mazda). Since the fuel passes through the intake runners (like a carburetor system), it is called a "wet manifold system".

The justification for single-point injection was low cost. Many of the carburetor's supporting components- such as the air cleaner, intake manifold, and fuel line routing- could be reused. This postponed the redesign and tooling costs of these components. Single-point injection was used extensively on American-made passenger cars and light trucks during 1980-1995, and in some European cars in the early and mid-1990s.

Continuous injection




Central port injection


Multiport fuel injection

Multiport fuel injection injects fuel into the intake ports just upstream of each cylinder's intake valve, rather than at a central point within an intake manifold. MPFI (or just MPI) 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; or simultaneous, in which fuel is injected at the same time to all the cylinders. The intake is only slightly wet, and typical fuel pressure runs between 40-60 psi.

Many modern EFI systems utilize sequential MPFI; however, in newer gasoline engines, direct injection systems are beginning to replace sequential ones.

Direct injection

See also: Common rail




Diesel engines



Throughout the early history of diesels, they were always fed by a mechanical pump with a small separate chamber for each cylinder, feeding separate fuel lines and individual injectors.[citation needed] Most such pumps were in-line, though some were rotary.


Gasoline engines

Modern gasoline engines also utilise direct injection, which is referred to as gasoline direct injection. This is the next step in evolution from multi-point fuel injection, and offers another magnitude of emission control by eliminating the "wet" portion of the induction system along the inlet tract.


Swirl injection

Swirl injectors are used in liquid rocket, gas turbine, and diesel engines to improve atomization and mixing efﬁciency.

The circumferential velocity component is ﬁrst generated as the propellant enters through helical or tangential inlets producing a thin, swirling liquid sheet. A gas-ﬁlled hollow core is then formed along the centerline inside the injector due to centrifugal force of the liquid sheet. Because of the presence of the gas core, the discharge coefﬁcient is generally low. In swirl injector, the spray cone angle is controlled by the ratio of the circumferential velocity to the axial velocity and is generally wide compared with nonswirl injectors.[27]

Maintenance hazards



  1. ^ Hartmann, Gerard (2007-08-05). "Les moteurs et aéroplanes Antoinette" [Antoinette engines and aeroplanes] (PDF) (in French). hydroretro.net. Retrieved 2014-01-20. 
  4. ^ "The Direct Injection Engine Will Likely Power Your Next Car". HybridKingdom.com. 2009. Retrieved 2014-01-20. 
  5. ^ "1940 6C 2500 Touring "Ala Spessa"" (in Italian). digilander.libero.it. Retrieved 2014-01-20. 
  6. ^ Gerard Hartmann (2007-08-05). "Les moteurs et aéroplanes Antoinette" [Antoinette engines and aeroplanes] (PDF) (in French). Retrieved 2014-04-08. 
  9. ^ Circle Track, 9/84, pp.82-3.
  10. ^ a b Walton, Harry (1957-03). "How Good is Fuel Injection?". Popular Science 170 (3): 88–93. Retrieved 2014-01-20.  Check date values in: |date= (help)
  11. ^ Davis, Marlan (2010-10). "What You Need To Know About Mechanical Fuel Injection". Hot Rod Magazine. Retrieved 2014-01-20.  Check date values in: |date= (help)
  12. ^ Ingraham, Joseph C. (1957-03-24). "Automobiles: Races; Everybody Manages to Win Something At the Daytona Beach Contests". The New York Times. p. 153. Retrieved 2014-01-20. 
  13. ^ Consumer Reports 22: 154. 1957. 
  15. ^ "An Invitation to Happy Motoring... (Excerpts from the 1957 Rambler Rebel Owner's Manual)". AMX-files.com. Archived from the original on 2009-03-28. Retrieved 2014-01-20. 
  16. ^ a b Auto Editors of Consumer Guide (2007-08-22). "Rambler Measures Up". Retrieved 2014-01-20. 
  18. ^ Kendall, Leslie. "American Musclecars: Power to the People". Petersen Automotive Museum. Archived from the original on 2011-10-27. Retrieved 2014-01-20. 
  19. ^ "Celica Parts Catalogue" (in Japanese). Toyota. Retrieved 2014-01-20. 
  20. ^ 1975 Chevrolet Cosworth Vega Overhaul Supplement - general information
  21. ^ "A Timeline Overview of Motorola History 1928-2009". Motorola. Archived from the original on 2011-06-20. Retrieved 2014-01-20. 
  22. ^ Ryan, Nate (2011-11-02). "NASCAR sets fuel injection for '12 but keeping restrictor plates". USA Today. Retrieved 2014-01-20. 
  23. ^ "NASCAR Moves to Fuel Injection, Bosch First Approved Supplier". Auto Service World. 2011-07-18. Retrieved 2014-01-20. 
  24. ^ "Bosch to provide oxygen sensors for fuel injection". NASCAR.com. Archived from the original on 2011-12-25. Retrieved 2014-01-20. 
  26. ^ "IC Engines". Global Fuel Economy Initiative. Retrieved 2012-04-13. [dead link]

Further reading


External links