ME-SFI [ME] Start, post-start phase and warm-up enrichment, function - GF07.61-P-3014G
ENGINE 273 in MODEL 463.202/222/236/237 up to 31.5.12 as of model year 2009/YoM 08
Enrichment rate/time diagram
Function requirements for start phase, post-start phase and warm-up enrichment for the ME gasoline injection and ignition system (motor electronics) (ME), general points
- Circuit 87M ON (engine control ON)
- Engine running
ME-SFI start phase, post-start phase and warm-up enrichment, general points
To ensure stable and smooth engine running during a cold start, the ME-SFI [ME] control unit enriches the fuel-air mixture.
Start phase, post-start phase and warm-up enrichment, ME function sequence
The function sequence is divided into the following subfunctions:
- Starting mixture enrichment function sequence
- Post-start enrichment function sequence
- Warm-up enrichment function sequence
Starting mixture enrichment function sequence
To allow easier starting when the engine is cold, more fuel has to be injected during the start procedure.
For the starting mixture enrichment, the ME-SFI [ME] control unit calculates the injection time using the following sensors and signals:
- Coolant temperature sensor
- Crankshaft Hall sensor, engine speed
- Battery voltage (G1) through "circuit 30"
- EIS control unit, signal from circuit 50 via the drive train CAN
- Engine off time
Once it receives the "circuit 50 signal" from the EIS control unit via the chassis CAN, the ME-SFI [ME] control unit lengthens the injection time of the fuel injection valves (Y62).
Starting mixture enrichment remains active until the engine speed corresponding to the particular coolant temperature is exceeded. The higher the coolant temperature, the shorter is the injection time calculated by the ME-SFI [ME] control unit.
The injection times are also dependent on the battery voltage. In order to guarantee the start quantity for a low battery voltage, the ME-SFI [ME] control unit extends the injection times.
No further engine start is possible at a battery voltage of U < 7V.
Post-start enrichment function sequence
After a cold start the fuel-air mixture is enriched for a short time to ensure that the engine runs smoothly.
Fuel condensing in the cold cylinder barrels is compensated by the post-start enrichment.
The ME-SFI [ME] control unit calculates the injection time for the post-start enrichment according to the following sensors and signals:
- Coolant temperature sensor, coolant temperature at engine start
- Combustion cycles after start
- Electric controller unit (VGS), selector lever position via the drive train CAN
- Correction programming with the Diagnosis Assistance System (DAS)
The ME-SFI [ME] control unit assigns an additional quantity of fuel to the engine depending on the performance map.
To do this, the ME-SFI [ME] control unit extends the injection time of the injection valves.
Warm-up enrichment function sequence
After the start and post-start enrichment, the fuel-air mixture is further enriched by the warm-up enrichment.
The warm-up control compensates for fuel which precipitates on the still cold engine parts.
The ME-SFI [ME] control unit calculates the injection time for the warm-up enrichment using the following sensors and signals:
- Coolant temperature sensor
- Crankshaft Hall sensor, engine speed
- Hot film MAF sensor, engine load
- Intake air temperature sensor
- LH and RH intake camshaft Hall sensor, intake camshaft positions
- LH and RH exhaust camshaft Hall sensor, exhaust camshaft positions
- Correction programming using DAS
An additional quantity of fuel is added to the engine by the ME-SFI [ME] control unit in line with the performance map.
To do this, the ME-SFI [ME] control unit extends the injection time of the fuel injection valves.
The ignition angles of the ignition coils during warm-up are determined according to a specific performance map.
By using the LH and RH intake camshaft solenoids and the LH and RH exhaust camshaft solenoids the exhaust gas recirculation rate is determined by the valve overlap. As the hot exhaust gases heat up the combustion chambers, fuel evaporation is increased and fuel enrichment can be reduced.
In the idle speed range, injection time mainly depends on the coolant temperature at engine start.
On partial load, the crucial factor is engine load.
Once enabled, the lambda control monitors the injection time.
| Component description for ME-SFI [ME] control unit | N3/10 | GF07.61-P-6000G | |
| Component description for electronic ignition/starter switch control unit (EIS) | N73 | GF80.57-P-6000G | |
| Component description for fully integrated transmission control unit | Y3/8n4 | GF27.60-P-5165GGA |