GF07.16-P-2008IC CDI Preinjection, Function

GF07.16-P-2008IC CDI Preinjection, Function

Component Identification:

The injected quantity required by the engine is divided into the preinjection quantity and the main injection quantity Preinjection is divided into two injection phases to reduce noise and pollutant emissions (double preinjection).

Start of actuation of fuel injectors
The start of actuation of the fuel injectors is calculated according to the operating point of the CDI control unit. This takes place with consideration of the following:
^ Preinjection quantity
^ Start of actuation of main injection
^ Coolant temperature
^ Engine speed
^ Vehicle power supply voltage

Actuation duration of fuel injectors
The actuation duration of fuel injectors is calculated by the CDI control unit. This takes place with consideration of the following:
^ Preinjection quantity
^ Engine speed

Calculation of the individual injection quantities
The injection quantity is calculated by the CDI control unit using the following input signals:
^ Engine load
^ Engine speed
^ Coolant temperature
^ Charge air temperature
^ Charge air pressure
^ Rail pressure
^ Fuel temperature
^ Atmospheric pressure

Injection quantity = Preinjection quantity + Main injection quantity

The CDI control unit determines the preinjection quantity from its input signals according to performance mapping. The preinjection quantity is drawn from the injection quantity. If the resultant main injection quantity is less than a minimum quantity which is dependent on the rail pressure, no preinjection takes place.

Shutting off preinjection
Pre-injection is shut off depending on the operating point, if:
^ the preinjection time is exceeded
^ the engine speed is too high.
^ the preinjection quantity is too low.
^ the main injection quantity is too low.
^ the fuel pressure in the rail is inadequate.
^ the engine is switched off