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ME-SFI lambda control, function - GF07.61-P-4022AM

ENGINE 113.990 in MODELS 211, 219 

ENGINE 113.991 in MODELS 215, 220 

ENGINE 113.992 in MODEL 230 

ENGINE 113.993 in MODEL 463 

ENGINE 113.995 in MODEL 230 

Fig 1: ME-SFI Lambda Control Function Diagram
G04839952

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.

The O2 sensors upstream of TWC react to the oxygen share in the exhaust and transmits a corresponding voltage signal to the ME control unit. The ME control unit in turn alters the mixture composition by regulating the injection quantity in such a way that λ =1. This process is repeated constantly (control loop).

The lambda closed-loop control is operational in the following operating conditions (closed-loop control):

The ME control unit alters the mixture composition with a time delay in order to prevent any risk of jerking.

Fig 2: Exhaust Gas Conversion Graph
G04839953

Example: 

Assuming a leaner fuel-air mixture is produced. This has the following consequence, that the O2 sensor voltage drops and the ME control unit compensates for this lean drift through a matching enrichment.

This makes it possible to achieve a fuel-air mixture of approximately λ = 1.

The reading of the lambda control factor with the STAR DIAGNOSIS moves towards +25% The more the lambda control factor moves in the direction +25%, the leaner is the fuel-air mixture and the greater is the enrichment of the mixture on the part of the ME control unit.

Fig 3: Fuel-Air Mixture Chart
G04839954
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