GF07.10-P-1007MI Start, Post-Start Phase and Warm-Up Enrichment, Function

GF07.10-P-1007MI Start, Post-Start Phase And Warm-Up Enrichment, Function

Component Identification:

Function requirements for starting, the post-start phase and warm-up enrichment
^ Circuit 87M ON (engine control ON)
^ Engine running

Start phase, post-start phase and warm-up enrichment, general
To ensure stable and smooth engine running during a cold start, the ME-SFI [ME] control unit (N3/10) enriches the fuel-air mixture.

Start phase, post-start phase and warm-up enrichment, 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 (B11/4)
- Crankshaft Hall sensor (B70), engine speed
- vehicle electrical system battery voltage (G1) over "circuit 30"
- Electronic ignition lock control unit (N73), "circuit 50 signal" via the chassis CAN (CAN E)
- Engine off time

When it receives the "circuit 50 signal" from the electronic ignition lock control unit over the chassis CAN, the ME-SFI [ME] control unit extends the injection time of the 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 time is 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 time.

No further engine start is possible below an engine start of approx. 7 V.

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
- Fully integrated transmission control controller unit (Y3/8), selector lever position via the drive train CAN (CAN C) (for an automatic transmission)
- Correction programming with Xentry diagnostics

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 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
- Hot film MAF sensor (B2/5), engine load
- Intake air temperature sensor (B2/5b1)
- LH and RH intake camshaft Hall sensor (B6/4, B6/5), intake camshaft positions
- LH and RH exhaust camshaft Hall sensor (B6/6, B6/7), exhaust camshaft positions
- Coolant temperature sensor
- Crankshaft Hall sensor, engine speed
- Correction programming with Xentry diagnostics

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 control unit extends the injection time of the injection valves.
The ignition angles of the ignition coils (T1) during warm-up are determined according to a specific performance map.
The LH and RH intake camshaft solenoids (Y49/4, Y49/5) and the LH and RH exhaust camshaft solenoids (Y49/6, Y49/7) determine the valve overlap via the exhaust gas recirculation rate. 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.