KE-Motronic injection system parts (Audi 100 C4)

Throttle valves

In one of the intake manifold pipes there are two throttle valves. The smaller of these valves is connected by a cable to the gas pedal in the car. It regulates the air supply to the engine up to about half the gas pedal stroke. When the gas pedal is pressed further, the drive opens the second, larger valve. When the pedal is fully pressed, both throttle valves are fully open.

Mixture regulator

This is one of the main parts of the injection system, includes an air quantity meter and a fuel dispenser. They function as follows:

• The light metal plate of the air quantity meter is located along the air flow to the engine. This plate is lifted during the piston stroke during the intake stroke and the more the more air needs to be supplied to the throttle valve. The amount of rotation of the plate is transmitted to the fuel dispenser using a system of levers.
• The fuel metering device consists mainly of a distribution piston and a housing with slots. For each engine cylinder, the housing has its own slot, through which the fuel flows to the corresponding injector. The distribution piston closes or opens the slot more or less and, in accordance with the position of the air-measuring plate, passes the required amount of fuel.
• System pressure: The fuel pump supplies fuel under pressure to the injection system. The first stage of the pressure regulator is located here in a separate housing. It releases excess pressure and leaves a pressure of 6.6 bar in the fuel system. This pressure is present in the dispenser, fuel lines and injectors.

Pressure regulator

The pressure regulator, together with the vacuum chambers, determines the amount of mixture. This is done with the help of pressure differential valves, which usually perform a different task. Fuel supply to the vacuum chambers (from which the required amount of mixture comes out) is carried out using a pressure regulator. If it passes a lot of fuel to the vacuum chambers, the pressure inside the chambers increases, causing the membranes of the pressure differential valves to bend in the direction of the valve openings. Less fuel is supplied to the injectors. The reverse action occurs in the same way. The pressure regulator receives control signals from the control unit. In this case, lambda regulation, temperature and engine load are taken into account. The pressure regulator is located on the side of the mixture regulator.

Injectors

They inject fuel into the fuel channel in front of the inlet valve of the corresponding cylinder until the fuel pressure reaches 3.7-4.8 bar (depending on the engine type) At the same time, they open up to 200 times per second, thanks to which the fuel can be atomized particularly finely.

Pressure regulator

The pressure regulator, together with the vacuum chambers, determines the amount of mixture. This is done with the help of pressure differential valves, which usually perform a different task. Fuel supply to the vacuum chambers (from which the required amount of mixture comes out) is carried out using a pressure regulator. If it passes a lot of fuel to the vacuum chambers, the pressure inside the chambers increases, causing the membranes of the pressure differential valves to bend in the direction of the valve openings. Less fuel is supplied to the injectors. The reverse action occurs in the same way. The pressure regulator receives control signals from the control unit. In this case, lambda regulation, temperature and engine load are taken into account. The pressure regulator is located on the side of the mixture regulator.

Injectors

They inject fuel into the fuel channel in front of the inlet valve of the corresponding cylinder until the fuel pressure reaches 3.7-4.8 bar (depending on the engine type) At the same time, they open up to 200 times per second, thanks to which the fuel can be atomized particularly finely.