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

ENGINES 113.967 in MODEL 219 

ENGINES 113.964 in MODEL 164.1 up to model year 2008/AEJ 07 

ENGINES 113.971 in MODEL 251 up to model year 2008/AEJ 07 

Shown on model 219 

Fig 1: ME-SFI Lambda Control Function Diagram
G07302073Courtesy of MERCEDES-BENZ USA

The mixture composition is maintained within limits as close as possible to λ=1 in order to achieve a high conversion of the exhaust gases in the catalytic converter.

The O 2 sensors upstream of the catalytic converter the oxygen concentration in the exhaust and transmit corresponding signals to the ME-SFI [ME] control unit. This changes the mixture composition so that in all engine operating statuses, the desired oxygen (usually λ=1) is set.

This procedure is repeated (control loop), the control speed is dependent on engine load and speed.

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

Fig 2: Graph Of Exhaust Gas Conversion Rate In Three Way Catalytic Converter
G07302074Courtesy of MERCEDES-BENZ USA
Fig 3: Lambda Control Loop
G07302075Courtesy of MERCEDES-BENZ USA

Lambda control loop 

Assuming a leaner air/fuel mixture is produced. The consequence of this is that the O2 sensor voltage drops and the ME-SFI [ME] control unit compensates for this lean drift by enriching the mixture accordingly.

This makes it possible to achieve an air/fuel composition 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 towards +25 %, the leaner is the air/fuel mixture and the greater is the enrichment of the mixture on the part of the ME-SFI [ME] control unit.

Fig 4: Lambda Control Factor
G07302076Courtesy of MERCEDES-BENZ USA
  Component description for ME-SFI [ME] control unit   GF07.61-P-6000BK 
  Component description for O 2 sensors   GF07.04-P-6100BK 
  Component description for crankshaft position sensor   GF07.04-P-6010BK 
  Component description for hot film mass air flow sensor   GF07.07-P-6000BK 
  Component description for coolant temperature sensor   GF07.04-P-6040BK 
  Component description for accelerator pedal sensor   GF30.20-P-2010BK
  Component description for three-way catalytic converter   GF07.03-P-6010BK 
  Self-adjustment of mixture formation, function   GF07.10-P-1029BK 
  ME-SFI two-sensor control, function   GF07.61-P-3020BK 
  Component description for three-way catalytic converter   GF49.10-P-2010BK