Fuel injection system – a fuel supply system, massively installed on gasoline automobile engines, since the 1980s. The main difference from the carburetor system is that the fuel is supplied by forced injection of fuel using nozzles into the intake manifold or into the cylinder. Cars with such a power system are often called injection cars. In aviation on piston engines, such a system began to be used much earlier – from the 1930s, but due to the low level of electronic equipment and precision mechanics of those years it remained imperfect. The advent of the jet era led to the cessation of work on fuel injection systems. The “second coming” injection into aviation (light-engine) occurred already in the late 1990s.
In the injection system, the fuel is injected into the air stream by special nozzles – injectors.
According to the installation point and the number of nozzles:
Mono – injection, central injection, or single-point injection – one nozzle on all cylinders, located, as a rule, in place of the carburetor (on the intake manifold ). Currently, it is unpopular due to increased environmental requirements: starting with Euro-3, the environmental standard requires an individual fuel dosage for each cylinder. Mono-injections were distinguished by simplicity and very high reliability, primarily due to the fact that the nozzle is in a relatively comfortable place, in a stream of cold air.
Distributed injection, or multi-point injection – each cylinder is serviced by a separate insulated nozzle in the intake manifold near the intake valve. At the same time, several types of distributed injection are distinguished:
Simultaneous – all nozzles open simultaneously.
Pairwise-parallel – nozzles open in pairs, with one nozzle opening immediately before the intake stroke, and the second before the exhaust stroke. Due to the fact that valves are responsible for the ingress of the fuel-air mixture into the cylinders, this does not have a strong effect. In modern engines, phased injection is used, pairwise parallel is used only at the time of engine start and in emergency mode when the camshaft position sensor (the so-called phase) breaks.
Phased injection – each nozzle is controlled separately and opens immediately before the intake stroke.
Direct injection – fuel is injected directly into the combustion chamber.
Currently, fuel supply systems are controlled by special microcontrollers, this type of control is called electronic. The principle of operation of such a system is based on the fact that the microcontroller takes the decision on the moment and duration of the nozzle opening based on the data received from the sensors. On early models of the fuel supply system, special mechanical devices acted as the controller.
Principle of Operation
When the system is operating, the controller receives information from the following sensors about the following parameters:
- position and speed of the crankshaft;
- mass air flow of the engine;
- coolant temperature;
- throttle position;
- the oxygen content in the exhaust gases (in a feedback system);
- the presence of detonation in the engine;
- voltage in the vehicle electrical system;
- vehicle speed;
- camshaft position (in a system with sequential distributed fuel injection);
- a request to turn on the air conditioner (if installed on the car);
- rough road (rough road sensor);
- incoming air temperature.
Based on the information received, the controller controls the following systems and devices:
- fuel supply (nozzles and gasoline pump),
- ignition system
- idle speed regulator
- the adsorber of the gas vapor recovery system (if this system is on the car),
- engine cooling fan
- air conditioning compressor clutch (if equipped);
- diagnostic system.
Changing the parameters of electronic injection can occur literally “on the fly”, since the control is carried out programmatically, and can take into account a large number of program functions and data from the sensors. Also, modern electronic injection systems are able to adapt the program of work for a specific instance of the engine, for the driving style and many other characteristics and specifications. Previously used a mechanical injection control system.
To quickly identify injector injuries, computer diagnostics of the fuel injection system are used.
Advantages compared to engines equipped with a carburetor fuel supply system (in the context of engines with an electronic control unit ):
- Significant reduction in fuel consumption even in early systems (for example, a Niva VAZ-21214 equipped with a first-generation injection system, fuel consumption is on average 30-40% less than a similar VAZ-21213 equipped with a carburetor). Modern systems provide fuel consumption about 2 times lower than the latest generations of carburetor cars of the same mass and displacement.
- A significant increase in engine power, especially in the low-speed region.
- Simplified and fully automated engine start.
- Automatically maintain the required idle speed.
- Broader engine control capabilities (improved dynamic and power characteristics of the engine).
- It does not require manual adjustment of the injection system, as it performs independent tuning based on data transmitted by oxygen sensors, as well as on the basis of measuring the unevenness of the crankshaft rotation.
- It supports approximately the stoichiometric composition of the working mixture, which significantly reduces the emission of unburned hydrocarbons and makes it possible to use redox catalytic converters. As a result, emissions of toxic combustion products decreased many times. For example, carbon monoxide emissions from the latest generations of carburetor cars were about 20-30 g / kW * h, from Euro-2 injection cars already 4 g / kW * h, and from cars manufactured according to Euro-5 standards – only 1, 5 g / kW * h
- Ample opportunities for self-diagnosis and self-tuning of parameters, which simplifies the process of car maintenance. In fact, injection systems, starting with Euro-3, generally do not require any periodic maintenance (only replacement of failed elements is required).
- The best car protection against theft. Having not received permission from the immobilizer, the engine control unit does not supply fuel to the engine.
- The possibility of reducing the height of the hood, since the elements of the injection system are located on the sides of the engine, and not above the engine, like most automobile carburetors.
- In carburetor systems when the engine is idle or when operating at low speeds due to the evaporation of gasoline from the carburetor, the entire tract, from the air filter to the intake valve, is filled with a combustible mixture, the volume of which in multi-cylinder engines is quite large. If there is a malfunction in the ignition system or improperly adjusted valve clearances, a flame may be emitted into the intake manifold and the combustible mixture will ignite, causing loud pops and may lead to fire or damage to the power supply devices. In injection systems, gas is supplied only at the moment of opening the inlet valve of the corresponding cylinder and the accumulation of the combustible mixture in the inlet tract does not occur.
- The operation of the carburetor depends on its position in space. For example, most automobile carburetors work with serious violations when the car roll is already 15 degrees. Injection systems have no such dependence.
The operation of the carburetor is highly dependent on atmospheric pressure, which is especially critical for the operation of automobile engines in the mountains, as well as for aircraft engines. Injection systems have no such dependence.
The main disadvantages of engines with a control unit compared to carburetor:
- The high cost of nodes (it was valid until about 2005),
- Low maintainability of elements (lost relevance in connection with the development of their mass production and increased reliability),
- High requirements for fractional composition of fuel,
- The need for specialized personnel and equipment for diagnostics, maintenance and repair, the high cost of repairs (lost relevance in connection with the mass distribution of mobile devices and diagnostic programs).
- Dependence on power supply and a critical requirement for a constant supply voltage (in the more modern version, controlled by electronics).
- The supply of gasoline under pressure, which in the event of an accident increases the likelihood of a fire. Therefore, in early systems, the circuit of the fuel pump had a circuit breaker that tripped upon impact, and in modern systems, the fuel pump is switched off in emergency situations by the controller.
The emergence and use of injection systems in aviation
Carburetor systems for working at an angle to the horizon must be supplemented with a variety of devices or use specially designed carburetors. The direct injection system of aircraft engines is a convenient alternative to the carburetor system, since the injection injection system, by virtue of its design, works in any position relative to the direction of gravity.
By 1936, the first sets of fuel equipment for direct injection of gasoline into cylinders were ready at Robert Bosch, which a year later they began to be mass-produced on a V-shaped 12-cylinder Daimler-Benz DB 601 engine. These engines with a volume of 33.9 liters were equipped, in particular, with the main Luftwaffe fighters Messerschmitt Bf 109. And if the carburetor engine DB 600 developed on take-off mode of 900 liters. s., the DB 601 with injection allowed to raise power to 1100 liters. c. and more. Later, the nine-cylinder BMW 132 star with a similar power system went into the series – a licensed Pratt & Whitney aircraft engine Hornet, which has been produced at BMW since 1928. It was installed, for example, on transport aircraft Junkers Ju 52. Aircraft engines in England, the USA and the USSR at that time were exclusively carbureted. The Japanese injection system on Mitsubishi A6M Zero fighters required flushing after each flight and therefore was not popular with the troops.
By the end of the war, they brought to the series their version of injection in the United States. For example, the engines of the “flying fortress” of the Boeing B-29 also powered gasoline through nozzles.
The beginning of the jet era led to the cessation of work on injection systems. Turbo-propeller and jet engines were used on heavy and high-speed aircraft, and piston engines were placed only on low-speed light, low-maneuverable aircraft and helicopters, which could work normally with a carburetor power system.
Application of injection systems in cars
Engine control systems in the automotive industry began to be used since 1951, when a 700 Sport two-stroke engine from the Goliath company from Bremen was equipped with a two-stroke engine from the West German firm Bosch, a mechanical direct gasoline injection system. In 1954, the Mercedes-Benz 300 SL coupe ( “gull wing” ) appeared, the engine of which was equipped with a similar mechanical Bosch injection system. At the turn of the 1950s and 1960s, Chrysler and GAZ actively worked on electronic fuel injection systems. Nevertheless, until the era of the emergence of cheap microprocessors and the introduction of strict requirements for the level of harmful emissions of cars, the idea of injection was not popular and only from the late 1970s did all the world’s leading automakers take up their implementation.
The first production model with electronic control of the gas injection system was the 1967 model year Rambler Rebel sedan, which was produced by Nash, which was part of AMC as a branch. The inferior v-shaped “eight” Rebel with a volume of 5.4 liters in the carburetor version developed 255 liters. with., and in the custom version of Electrojector already 290 liters. from. Acceleration to 100 km / h in such a sedan took less than 8 s.
By the early 2000s, distributed and direct electronic injection systems had virtually replaced carburetors in cars and light commercial vehicles.
Injection system manufacturers
Bendix injection system
- Electrojector is the first commercial electronic fuel injection system developed by Bendix. Electrojector injection patents were subsequently sold to Bosch.
Bosch Injection Systems
- D-Jetronic (1967-1976) – analog fuel injection. The system was originally called Jetronic , but was later renamed D-Jetronic
- K-Jetronic (1973-1994) – mechanical injection
- K-Jetronic (Lambda) – a variation of the K-Jetronic with a lambda sensor
- KE-Jetronic (1985-1993) – mechanical continuous fuel injection system, similar to the K-Jetronic system, but with an electronic control unit
- LE1-Jetronic, LE2-Jetronic, LE3-Jetronic (1981-1991)
- LU-Jetronic (1983-1991)
- LH-Jetronic (1982-1995)
- Mono-Jetronic (1988-1995) – single-point fuel injection system
- Motronic (1979)
- ME-Motronic (1995) – with electronic choke
- MED-Motronic (2000) – Direct Injection
- MEG-Motronic – Integrated Transmission Control
- MEV-Motronic – integrated valve lift control system
General Motors Injection Systems
- GM Multec Central – Central Fuel Injection System (Mono Injection)
- MulTec-S (Multiple Technology) – central fuel injection system
- Multec-F 1996-2001
- Multec-H 1998-2003
- MulTec-M – multipoint injection system
- Multec-U 1996-2001
- VAG Injection Systems
- Digifant – Distributed Fuel Injection System
- Digijet – distributed fuel injection system
Further Reading: How To Clean Your Fuel Injection System