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Fuel injection

Fuel injection


Fuel injection with the Motronic 4.1 is sequential, which means that it follows the firing order of the engine.

Injection duration is calculated by the engine control module, mainly on the basis of the following information:


• engine load (mass air flow sensor)

• engine speed (crankshaft position sensor)

• Coolant temperature

• oxygen content of the exhaust gases.


The opening duration of the injectors varies from about 3 ms at idling speed to about 15 ms at full load (wide open throttle) and a warmed-up engine. Fuel injection is cut off when engine speed exceeds 6400 rpm.

Pre-injection

To achieve shorter starting times, pre-injection takes place if the engine coolant temperature is below 0°C (32°F).

Pre-injection occurs as soon as the engine starts to turn over and the control module receives signals from the crankshaft position sensor. The control module then activates the fuel pump and all the injectors open simultaneously to squirt a small amount of fuel onto the inlet valves. The opening duration of the injectors is determined by the temperature of the coolant.

After this initial injection of fuel the system changes over to sequential fuel injection.