Self-adjustment of mixture formation, function - GF07.61-P-3030SM

ENGINE 113.986

ENGINE 113.987

ENGINE 113.988

ENGINE 113.989

Fig 1: Mixture Formation Self-Adjustment Graph (Engine 113)

On vehicles fitted with a closed-loop controlled catalytic converter the lambda control determines the injection time so exactly that a certain fuel-air ratio (λ) is maintained in all operating states.

If the following faults occur e.g.:

unmetered air,
worn or blocked fuel injection valves,
defective fuel pressure regulator,
defective hot film MAF sensor,
defective purge control valve,
wear to the engine (e.g. valve leakage)

N3/10 the ME control unit automatically performs a correction of the mixture formation. In this case, the lambda map is shifted within certain limits so that the lambda control is not positioned at the lower or upper control stop.

If the mixture composition constantly drifts out of the middle control range (e.g. 0 ± 10 %), the ME control unit under certain operating conditions shifts the lambda map 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 map is shifted (arrow) by the 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).

This self-adjustment of the mixture formation can be carried out in the following operating states:

Idle speed
Lower partial load (suction operation)
Upper partial load (pressure operation)

The following can be read out with STAR DIAGNOSIS:

whether the lambda performance map has shifted
The direction of the shift (rich or lean)
How far the lambda performance map has been shifted

Representation of self-adaptation values with STAR DIAGNOSIS:

The representation is performed in "ms" and means that the displayed value for determining the injection time is either added to or subtracted from the injection time determined by the performance map.

Example:

Calculated injection time (performance map): 3.0 ms

Displayed value in STAR DIAGNOSIS: +0.3 (ms)

For determining the injection time (quantity of fuel injected) the ME control unit uses a calculated value of 3.3 ms (3.0 ms+0.3 ms).

Correction values in idle

The maximum correction value is ± 1.0 ms.

Correction values in partial load

The maximum correction value is -0.68 +1,32 ms.

	O₂ sensor component description	G3/3, G3/4, G3/5, G3/6	GF07.04-P-6100SM
	ME-SFI [ME] control unit component description	N3/10	GF07.61-P-6000SM