Smooth Running Control, Function - GF07.10-D-1011TSC

Engine 642.8 in model 907 

Block diagram 

Function requirements for smooth running control, general points 

• Circuit 87M (engine timing ON)
• Engine running.

Smooth running control, general points 

Smooth running control reduces any rough running in the RPM range from about 750 to about 2,600 RPM.

For smooth running control, the CDI control unit (N3/28) reads in the following sensors and signals:

• Hot film MAF sensor (B2/14), engine load
• Coolant temperature sensor (B11/19)
• Crankshaft position sensor (B70/1), engine speed
• Accelerator pedal module (A68), accelerator pedal position via powertrain control unit (N127) and drive CAN (CAN C)
• ESP® control unit (N30/4), wheel speed signal via chassis FlexRay (Flex E), powertrain control unit (N127) and drive train CAN (CAN C)
• Fuel pump with fill level sensor (M3/6) via and fuel system control unit (N118/9) and drive CAN (CAN C)

Function sequence for smooth running control 

The function sequence is described in the following steps:

• Function sequence for combustion misfire detection
• Function sequence for sensor adaptation

Function sequence for combustion misfire detection  To do this, the CDI control unit reads the signal from the crankshaft position sensor and evaluates its regularity. If irregularities are found on the crankshaft position sensor signal, the CDI control unit corrects the fuel pressure in the rails via the pressure regulating valve (Y74/6) and the quantity control valve (Y94/4) and the injection duration via actuation of the fuel injectors (Y76).

The fuel pressure in the rails and the injection period of the fuel injectors combine to produce a specific injection quantity.

Function sequence for sensor adaptation 

The tolerance range for smooth running evaluation is reduced after successful adaptation of the crankshaft position sensor. In this way, the smooth running analysis can be adapted to the specific smooth running characteristics of the engine.

In overrun mode (accelerator pedal not pressed), if uniform smooth operation is present, the CDI control unit stores the engine's smooth running properties. These are required as a comparison parameter for misfire detection.

The tolerance range for smooth running analysis is preset in the CDI control unit and can be adapted using Xentry Diagnostics if necessary.

Electrical function schematic for smooth running control	PE07.10-D-2711-97TSC
Overview of system components for common rail diesel injection (CDI)	GF07.16-D-9997TSC