4.13. General information about fuel injection

The system of injection of fuel consists of three main subsystems: fuel system, system of an admission of air and electronic control system.

Fuel system

The electric fuel pump located in or near the fuel tank gives fuel under pressure to the fuel highway which distributes fuel evenly between all injectors. From the fuel highway fuel is injected into the input device of an injector located under the inlet valve. The amount of fuel injected by an injector precisely is defined by the Electronic control unit (ECU). At launch of the engine the additional injector known as the injector of cold start-up (only on the L-Jetronic systems and the early Motronic systems), provides giving in the inlet pipeline of additional amount of fuel.

Pressure regulator according to discharge size in the inlet pipeline operates pressure in system.

The fuel filter between the fuel pump and the fuel highway filters fuel to protect system components.

System of an admission of air

The system of an admission of air consists of the case of the air filter, the measuring instrument of a stream of air, the case of a throttle, the inlet pipeline and the related air ducts. The measuring instrument of an air stream transfers information to ECU. These models are equipped with the measuring instrument of a stream of flyugerny type. Measurement of an inlet stream of air is performed by a potentiometer, and the sensor of temperature takes temperature of inlet air. This information helps ECU to define amount of the fuel (injection duration) injected by injectors. The butterfly valve in the case of a throttle is operated by the driver. When the butterfly valve opens, the amount of the air passing through system increases, the signal of a potentiometer increases and ECU operates injectors on increase in amount of the fuel given to inlet devices.

Electronic control system

The processor control system operates fuel and other systems by means of the Electronic control unit (ECU). ECU receives signals from a set of information sensors which trace such changing parameters as volume of the let-in air, temperature of the let-in air, cooler temperature, engine turns, acceleration/delay and content of oxygen in the fulfilled gases. These signals help ECU to determine the injection duration necessary for achievement of an optimum ratio air/fuel. These sensors and corresponding to them the actuation mechanisms operated by ECU are located on all motive compartment. For the further data concerning ECU and its interaction with electric systems of the engine and system of ignition address Heads System of ignition and Control system of the engine and decrease in toxicity of the fulfilled gases.

Either the L-Jetronic system, or Motronic are applied. Late models are equipped with the modern version of the initial Motronic system.