CDI preinjection, function - GF07.16-P-2008P

ENGINES 642 in MODEL 203.0, 164.1/8, 221.1/0, 251.0, 203.2, 251.1 up to model year 2008/YoM 07 

ENGINES 642.9 in MODEL 463.3 

ENGINES 642 in MODEL 461.3 

ENGINES 642 in MODEL 211.6, 219.3, 209.4/3, 211.2/0 

The objective of preinjection is to reduce combustion noise. This is achieved by injecting fuel one or two times before the main injection starts to make the combustion run smoother. Preinjection also leads to reduction of the particulate matter (particles) (PM) in the exhaust gas. The start of actuation of the fuel injectors (Y76) during preinjection is calculated by the CDI control unit (N3/9) according to the load. Furthermore the last beginning of actuation of the main injection and the on-board electrical system voltage of the battery (G1) (model 164, 203, 209, 211, 219, 251, 461, 463) or the on-board electrical system battery (G1) (model 221) is taken account of. The preinjection quantity is calculated by the CDI control unit. To do this, it reads information from the following sensors:

• Rail pressure sensor (B4/6), for the rail pressure
• Boost pressure sensor (B5/1), for the boost pressure
• Coolant temperature sensor (B11/4), for the coolant temperature
• Charge air temperature (B17/8), for the charge air temperature
• Pressure sensor downstream of air filter (B28/5), for the absolute pressure (vacuum) in the intake tract (except model 463)
• Pressure sensor downstream of air filter, right cylinder bank (B28/5), for the absolute pressure (vacuum) in the intake tract (only model 463)
• Crankshaft Hall sensor (B70), for the engine speed

Preinjection is not initiated by the CDI control unit if one of the following statuses is present:

• The preinjection time is exceeded
• The preinjection quantity is too low
• The detected engine speed is too high
• The quantity of main injection is too low
• The rail pressure is too low
• The engine is switched off

The coolant temperature, the charge air temperature and the absolute pressure (vacuum) in the intake tract are used to correct the preinjection quantity.