Start, Post-Start Phase And Warm-Up Enrichment, Function - GF07.10-P-1007MRT
Engine 256.9 in model 213, 238, 257, 290
up to model year 2021
Engine 256.9 in model 222
Function requirements, general
- Circuit 50 ON
The electronic ignition lock control unit (N73) transmits the terminal status terminal 50 via the suspension FlexRay (Flex E), powertrain control unit (N127), and drive CAN (CAN C1) to the ME-SFI [ME] control unit (N3/10).
Start phase, post-start phase and warm-up enrichment, general
The ME-SFI [ME] control unit enriches the fuel/air mixture in order to achieve stable and smooth engine running in the case of a cold start.
Enrichment rate/time diagram
Starting mixture enrichment
To allow easier starting when the engine is cold, more fuel has to be injected during the starting procedure.
The ME-SFI control unit calculates the injection duration for starting mixture enrichment based on the following signals:
- Coolant temperature
Coolant temperature sensor (B11/4)
- Engine speed
Crankshaft Hall sensor (B70)
The ME-SFI [ME] control unit additionally extends the injection duration for starting mixture enrichment depending on the engine off time.
The ME-SFI [ME] control unit calculates the required injection duration and accordingly actuates the following components of the fuel injection system:
- Cylinder 1 fuel injector (Y76/1)
- Cylinder 2 fuel injector (Y76/2)
- Cylinder 3 fuel injector (Y76/3)
- Cylinder 4 fuel injector (Y76/4)
- Cylinder 5 fuel injector (Y76/5)
- Cylinder 6 fuel injector (Y76/6)
The ME-SFI [ME] control unit actuates the following ignition system components:
- Cylinder 1 ignition coil (T1/1)
- Cylinder 2 ignition coil (T1/2)
- Cylinder 3 ignition coil (T1/3)
- Cylinder 4 ignition coil (T1/4)
- Cylinder 5 ignition coil (T1/5)
- Cylinder 6 ignition coil (T1/6)
Starting mixture enrichment remains active until the engine speed dependent on the particular coolant temperature is exceeded. The higher the coolant temperature, the shorter the injection duration calculated by the ME-SFI [ME] control unit.
Additional post-start enrichment function requirements
- Engine runs
The ME-SFI [ME] control unit detects engine running by evaluating the crankshaft Hall sensor signals. The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
Post-start enrichment
After a cold start, the fuel/air mixture is enriched for a short time to stabilize engine running. The quantity of fuel condensing on the cold cylinder barrels is compensated by the post-start enrichment. The ME-SFI [ME] control unit extends the injection duration for this purpose. The ME-SFI [ME] control unit calculates the injection duration on the basis of the signals from the coolant temperature sensor. In addition, the ME-SFI [ME] control unit evaluates the combustion cycles after the start, and the transmission selector lever position. The control unit for the fully integrated transmission control electric controller unit (Y3/8n4) transmits information about the engaged drive range via the drive CAN to the ME-SFI [ME] control unit.
Additional warm-up enrichment function requirements
- Engine runs
The ME-SFI [ME] control unit detects engine running by evaluating the crankshaft Hall sensor signals. The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
Warm-up enrichment
Following start and post-start enrichment, the fuel/air mixture undergoes further enrichment by means of warm-up enrichment. The quantity of fuel condensing on the still cold cylinder barrels is compensated by the warm-up enrichment. The ME-SFI [ME] control unit extends the injection duration for this purpose.
The ME-SFI control unit calculates the injection duration for warm-up enrichment based on the following signals:
- Intake camshaft position
Intake camshaft Hall sensor (B6/15)
- Exhaust camshaft position
Exhaust camshaft Hall sensor (B6/16)
- Coolant temperature
Coolant temperature sensor
- Engine load
Pressure and temperature sensor downstream of turbocharger (B28/17)
- Engine speed
Crankshaft Hall sensor
The exhaust gas recirculation is activated while still in the warm-up phase. The hot exhaust provides additional heating of the combustion chambers. This improves the fuel evaporation and the warm-up enrichment can be reduced.
In neutral, the injection duration is primarily dependent on the coolant temperature when the engine starts. For partial load, the crucial factor is the engine load. Once enabled, the lambda control monitors the injection period.
| Electrical function schematic for start phase, post-start phase and warm-up enrichment | Engine 256.9 in model 213, 238 up to model year 2021 | PE07.10-P-2707-97DBA | |
| Engine 256.9 in model 222 | PE07.10-P-2707-97SEM | ||
| Engine 256.9 in model 257 up to model year 2021 | PE07.10-P-2707-97XBB | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MRT |