Operation - Interaction of Components

Starting: The vacuum created by the engine's intake pistons lifts the check valve in the air flow meter. As a result, the control plunger allows fuel to flow to the injection valves. While the starter is operating, the cold start valve supplies additional fuel to the intake system if the engine is still cold. Only in this case does the control unit allow this injection. The maximum injection duration also depends on temperature.

Warm-up phase: To ensure the engine runs smoothly during the first minutes after starting, the idle stabilization control valve opens a passage through which intake air can bypass the throttle valve.

In addition, the pressure regulator delivers more fuel through the injection valves. The increased supply of air and fuel allows a higher engine speed during the warm-up phase with an enriched mixture.

As engine temperature rises, the control valve progressively closes off the air passage. At the same time, the fuel supply returns to normal, and the pressure regulator reduces the amount of injected fuel.

Idle: To maintain a steady engine speed at idle and smooth response at low engine speeds, air is supplied to the combustion chamber around each injection valve. This results in finer fuel atomization. The air flows to the injection valves through a connecting fitting in the cylinder head and a special air passage. The idle speed control valve allows more intake air to bypass the throttle valve if engine speed drops below the specified value.

Normal operation and acceleration do not require any special devices. The control valve flap in the air flow meter rises or falls depending on the volume of air drawn in. Fuel supply to the injection valves changes accordingly: more air means more fuel, less air means less fuel. In this way, the correct and most favorable air-fuel ratio for combustion is always established automatically.

Full load: When the accelerator pedal is fully depressed, the throttle valve angle sensor signals the control unit that maximum engine power is required. The pressure regulator is thereby commanded to supply slightly more fuel to the injection valves than normal.

Deceleration fuel cut-off (overrun): The deceleration fuel cut-off function shuts off the fuel supply when the vehicle is traveling downhill and the accelerator pedal is not depressed.