GF07.10-P-1029CY Self-Adjustment of Mixture Formation, Function

GF07.10-P-1029CY Self-adjustment Of Mixture Formation, Function
- up to model year 08

Component Identification:

For regulated catalytic converters the lambda control determines the injection time so exactly that a certain fuel-air ratio (lambda) is maintained under all operating conditions.

The following faults can occur:
^ Unmetered air
^ Wear or coking of the injection valves (Y62)
^ Damaged pressure sensor (B28)
^ Transition resistance in the hot film mass air flow sensor (B2/5)
^ Defective purge control valve (Y58/1)
^ Harmful fuel pressure regulator
^ Wear to the engine (e.g. valve leakage)

If a fault occurs, the ME-SFI [ME] control unit (N3/10) automatically makes a correction in the mixture formation. Here the lambda performance map is shifted within certain limits in such a way that the lambda control is not at the upper or lower regulator stop.

If the mixture composition constantly drifts out of the middle control range (e.g. 0±10%), the ME-SFI [ME] control unit shifts the lambda map under certain operating conditions sufficiently far until a lambda control factor of approx. 0% (g) is again achieved.

Self-adjustment ensures that the mixture composition in the control mode (e.g. warming-up phase) is neither too rich nor too lean. This also prevents the lambda control from moving up to the control limit at high altitudes.

Example:
As the result of a lean fuel/air mixture the readout of the lambda control factor changes to 18% (e). Under certain operating conditions the lambda performance map is shifted (arrow) by the ME-SFI [ME] control unit.
This shifting of the lambda map is the self-adaptation of the mixture formation to the existing fuel-air mixture.
After this self-adjustment the lambda control factor is again in the central control range (g).

Self-adjustment of the mixture formation can be carried out in the following operating states:
^ Idle speed
^ Lower part load
^ Upper part load

The following can be read out using the DAS:
^ Whether the lambda performance map has been shifted
^ The direction of the shift (rich or lean)
^ How far the lambda performance map has been shifted

Presentation of self-adjustment value using the DAS
Presentation takes place in the form of a factor and means that the measured air mass value is multiplied by the factor.

Example:
Measured air mass: 150.0 kg/hour
Indicated factor in the DAS: 1.1

To determine the injection duration (fuel injection quantity), the ME-SFI [ME] control unit uses a mathematical air mass value of 165 kg/h (150 kg/hX1.1).

The maximum correction value is -0.68 to +1.32 ms.