GF07.10-P-1011OG Smooth Running Control, Function

GF07.10-P-1011OG Smooth Running Control, Function
ENGINES 642.8 in MODEL 204.0 /2 /9, 207.3 /4, 212.0 /2, 218.3

Function requirements for smooth running control, general points
^ Circuit 87 ON (engine control ON)
^ Engine running

Smooth running control, general
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 mass air flow sensor (B2/6), engine load
- Right hot film mass air flow sensor (B2/7), engine load
- Coolant temperature sensor (B11/4)
- Instrument cluster (A1), fuel level via the chassis CAN (CAN E)
- Electrically stability program control unit (N30/4) (except code (233) DISTRONIC PLUS) or Premium electrically stability program control unit (N30/7) (with code (233) DISTRONIC PLUS), wheel speed signal via the chassis CAN
- Accelerator pedal sensor (B37), accelerator pedal position
- Crankshaft Hall sensor (B70), engine speed

The Electronic Stability Program control unit (N30/4) will be used as of 1.3.2011 (model 204.0/2) in 2 variants:
- Electronic Stability Program control unit, basis variant (except code (233) DISTRONIC PLUS)
- Electronic Stability Program control unit, Premium variant (except code (233) DISTRONIC PLUS)

Until 28.2.2011 (model 204.0/2) or 31.5.2011 (model 204.9) and as of 1.6.2011 (model 204.9) only the basic variant of the Electronic Stability Program control unit will be used.

Function sequence for smooth running control
The function sequence is described in the following steps:

^ Function sequence for combustion misfire detection
^ Function sequence for factors for smooth running control

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).

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

Function sequence for factors for smooth running control
The following factors affect smooth running control:

^ Recognition of road bumps
^ Fuel reserve signal
^ Sensor adaptation

Recognition of an uneven road surface
Vibrations transmitted through the drive train may have a negative effect on engine running at certain engine speeds and load conditions. Therefore, the tolerance range for smooth running analysis is increased on poor road surfaces ("wash board").

The CDI control unit receives the wheel speed signal (for detection of uniform wheel rotation) from the Electronic Stability Program control unit over the chassis CAN.

Fuel reserve signal
The SAM control unit with rear fuse and relay module (N10/2) evaluates the signals from the LH and RH fuel level indicator sensors (B4/1, B4/2) and sends the corresponding signal over the body CAN (CAN B) to the instrument cluster.
The CDI control unit receives information about the fuel level via the chassis CAN from the instrument cluster.

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