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 O2 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 = 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 O2 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 O2
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 | ||
| Component description for ME-SFI [ME] control unit | N3/10 | Engine 273 | GF07.61-P-6000MLS | |