Smooth running control, function

Function requirements for smooth running control, general points

 Circuit 87M (engine timing ON)

 Engine runs

Smooth running control, general points

Smooth running control reduces any rough running in the engine rpm range from 750 to 2600 rpm.

For smooth running evaluation, the CDI control unit (N3/9) reads in the following sensors and signals:

– left hot film MAF sensor (B2/6), engine load

– right hot film MAF sensor (B2/7), engine load

– coolant temperature sensor (B11/4)

- accelerator pedal sensor (B37), accelerator pedal position

- crankshaft Hall sensor (B70), engine speed

- Electronic Stability Program control unit (N30/4), wheel speed signal via chassis FlexRay (Flex E), powertrain control unit (N127) and drive train CAN (CAN C1)

- Left fuel tank fuel level indicator fill level sensor (B4/1) and right fuel tank fuel level indicator fill level sensor (B4/2) via fuel system control unit (N118) and drive train CAN (CAN C1) to the CDI control unit.

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

Here the CDI control unit reads in the signal from the crankshaft Hall sensor and evaluates its regularity. If irregularities are found on the crankshaft Hall sensor signal, the CDI control unit corrects the fuel pressure in the rails via the pressure regulating valve (Y74) and the quantity control valve (Y94) and the injection time via actuation of the fuel injectors (Y76).

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

Function sequence for sensor adaptation

The tolerance range for smooth running analysis is reduced after successful adaptation of the crankshaft Hall sensor.

In this way, the smooth running analysis can be adapted to the specific smooth running characteristics of the engine.

The CDI control unit stores the smooth operation characteristics of the engine during a deceleration phase (accelerator pedal not operated) when uniform smooth operation is present. These are required as a comparison parameter for misfire detection.

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