ME-SFI lambda control, function - GF07.61-P-4022CY
ENGINE 272.911 in MODEL 204.0 up to Model Year 8
ENGINE 272.921 in MODEL 204.0 /2 up to Model Year 8
ENGINE 272.947 in MODEL 204.0 /2 up to Model Year 8
ENGINE 272.948 in MODEL 204.0 up to Model Year 8
ENGINE 272.961 in MODEL 204.0 /2 up to Model Year 8
ENGINE 272.971 in MODEL 204.0 up to Model Year 8
The mixture composition is controlled within the narrowest possible limits around λ = 1 in order to achieve a high conversion of the exhaust gases (exhaust gas conversion) in the catalytic converters.
Oxygen sensors on the left and right upstream of the TWC (G3/3, G3/4) react to the oxygen portion in exhaust gas and send appropriate voltage signals to the ME-SFI [ME] control unit (N3/10). Consequently, the mixture composition is modified by control of the injection quantity, so that λ=1 is obtained. This process is repeated constantly (control loop).
The ME-SFI [ME] control unit alters the mixture composition with a time delay in order to prevent any risk of jerking.
Control of the air/fuel ratio is much faster by using a wideband oxygen sensor (continuous signal of λ 0.7 to 4.0) than an oxygen sensor upstream of TWC.
The function of the lambda control (closed-loop operation) is dependent upon:
- Coolant temperature >-10°C
- Blocking time after starting expired
- Operating temperature of the oxygen sensors upstream of catalytic converter
- Engine idling or partial-load range
- Deceleration fuel shutoff not active.
Exhaust gas conversion in the three way catalytic converter
Example:
Assuming a leaner fuel-air mixture is produced. This has the following consequence, that the oxygen sensor voltage drops and the ME-SFI [ME] control unit compensates for this lean drift by making a matching enrichment.
This makes it possible to achieve a fuel-air mixture of approximately λ = 1.
Readout of the lambda control factor with the DAS alters in the direction +25%.
The more the lambda control factor moves in the direction +25 %, the leaner is the fuel-air mixture and the greater enrichment of the mixture on the part of the ME-SFI [ME] control unit.