ME-SFI lambda control, function - GF07.61-P-4022MIS
ENGINE 272.9 in MODEL 221.0 /1 as of model year 2009 / AEJ 08
ENGINE 273.9 in MODEL 216.3, 221.0 /1 as of model year 2009 / AEJ 08
Exhaust gas conversion in the three way catalytic converter
Function requirements for lambda regulation, general points
- Circuit 87M ON (engine control ON)
- Engine running
- Coolant temperature > -10°C
- Operating temperature reached in LH and RH O 2 sensors upstream of the catalytic converter (G3/3, G3/4)
- Engine idling or partial-load range
- Deceleration fuel shutoff not active.
Lambda regulation, general points
The mixture composition is controlled within the narrowest limits around λ = 1 in order to achieve high conversion of the exhaust gases (exhaust gas conversion) in the catalytic converters.
For this purpose, the ME-SFI [ME] control unit (N3/10) reads the following sensors:
- Hot film MAF sensor (B2/5), engine load
- Coolant temperature sensor ()B11/4
- LH and RH O2 sensors upstream of catalytic converter, oxygen sensor signals
Lambda regulation function sequence
The O 2 sensors upstream of the catalytic converter react to the oxygen content in the exhaust and send the corresponding voltage signals to the ME-SFI [ME] control unit. This then regulates the mixture composition by adjusting the injection time of the fuel injection valves (Y62) so that λ =1 is reached. 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) as O 2 sensors upstream of the catalytic converter.
Example:
Assuming a leaner fuel-air mixture is produced. As a result, the oxygen sensor voltage drops and the ME-SFI [ME] control unit compensates for the leaner mixture by enriching it accordingly (extending the injection time).
This makes it possible to achieve a fuel-air mixture of approximately λ = 1.
The lambda control factor indicated with the Diagnosis Assistance System (DAS) changes 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-SFI [ME] control unit.
| Electrical function schematic, lambda control ME | Model 216 | PE07.61-P-2774-97CAB | |
| Model 221 | PE07.61-P-2774-97SAB | ||
| Component description for ME-SFI [ME] control unit | N3/10 Engine 272 except 272.974 (Hybrid) |
GF07.61-P-6000MIS | |
| N3/10 Engine 272.974 (Hybrid) |
GF07.61-P-6000MEH | ||
| N3/10 Engine 273 |
GF07.61-P-6000MLS |