Operation of the petrol injection system

The electric fuel pump draws fuel from the fuel tank and delivers it through the underbody filter to the injection unit. The pressure regulator keeps the fuel pressure in the system constant (depending on the engine, the overpressure is 2.7-3.0 bar).

Valve injectors are electromagnetically controlled and inject fuel intermittently, i.e. in portions, into the intake manifold just before the intake valves. The engine control unit regulates the duration of injection and thus the amount of fuel injected.

The air required for combustion is drawn in by the engine through the air filter and passes through the throttle valve assembly and intake manifold to the intake valves. The amount of air intake is regulated by a throttle valve, which the driver controls through the accelerator pedal and throttle linkage. The amount of air taken in is determined by the volumetric air flow meter. In the body of the volumetric air flow meter there is a pressure damper, which is deflected to a certain position by the pressure of the incoming air and is held in this position. The damper angle is a measure of the amount of incoming air. The corresponding signals are transmitted to the control unit via a potentiometer.

The engine control unit is a small, very fast computer. It calculates the optimum ignition timing, injection start time and the amount of fuel injected. Signals from various sensitive elements and sensors allow you to correctly dose the amount of injected fuel in any traffic situation.

If important sensors fail, the control unit switches to a backup program. This allows you to avoid engine damage and continue driving further. In this case, the engine runs unevenly and when you press the gas pedal is prone to damping.