When the ignition is switched on, initially fuel is briefly injected once at all cylinders.Once the start procedure has been initiated, fuel is then injected cylinder-selective 1x per working cycle (2 crankshaft revolutions).
The injection timing (ti) is derived from the programmed basic start injection quantity and the correction variables from the input signals for coolant and intake air temperature. Cylinder activation is based on the position of the reference mark signal.
After few engine revolutions (dependent on the position of the camshaft and the start speed) the DME control unit receives the signal from the camshaft position sensor.
Double ignition (one ignition during each crankshaft revolution) takes place until the camshaft position is detected. It can now be seen whether the ignition allocation needs correcting.
The double ignition function is retained if the camshaft position sensor signal is not detected with the engine running. In this case, it is not guarantied that the ignition timing takes place within the working cycle.
Acceleration enrichment is always activated when the load requirement of the driver (throttle potentiometer signal) and the engine speed render this necessary. Intermediate injection takes place at the cylinders which have already completed their injection time cycle.For the subsequent cylinders, the normal injection timing (ti) is extended for fuel enrichment.
The DME M3.3 features cylinder-individual fuel injection CIFI. The term CIFI refers to individual activation of each cylinder.The system ensures that fuel injection of each cylinder is completed before the the inlet valve opens. An optimum fuel-air mixture and thus improved combustion with low fuel consumption is achieved in this way.
The output stage of each cylinder can be switched off individually if there is a fault in the ignition or fuel injection system. These faults are then also stored in the defect code memory.