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ME-SFI lambda control, function engine 113 - GF07.61-P-4022SM

ENGINE 113.986 

ENGINE 113.987 

ENGINE 113.988 

ENGINE 113.989 

Fig 1: ME-SFI Lambda Control, Function (Engine 113)
G04738448Courtesy of MERCEDES-BENZ USA

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 converter.

The O2 sensors (G3/3, G3/4) react to the oxygen share in the exhaust and transmit a corresponding voltage signal to the ME control unit (N3/10). This alters the mixture composition by controlling the injection quantity so that λ=1 is obtained. 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: Lambda Control Loop Flow Diagram
G04738449Courtesy of MERCEDES-BENZ USA

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: Lambda Control Factor (Display With STAR Diagnosis)
G04738450Courtesy of MERCEDES-BENZ USA
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