GF07.61-P-3014MOR ME-SFI [ME] Start, Post-Start Phase and Warm-Up Enrichment, Function

GF07.61-P-3014MOR ME-SFI [ME] Start, Post-Start Phase And Warm-Up Enrichment, Function
- refinement package
- as of model year 09

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 position sensor (L5), engine speed
- Engine off time
- Atmospheric air pressure sensor in the ME-SFI [ME] control unit, altitude adaptation
- EIS control unit (N73), circuit 50 signal over the engine compartment CAN (CAN C)
- On-board electrical system battery voltage (G1) through "circuit 30"

When it receives the "circuit 50 signal" from the EIS control unit over the engine compartment CAN, the ME-SFI [ME] control unit extends 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.

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
- ETC control unit (N15/3), selector lever position over the engine compartment CAN
- Correction programming using 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.

The fuel is enriched until a certain engine speed is set (for example,1400 rpm if selector lever position is "P" and coolant temperature is +30 °C for about 30 s).

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
- Charge air temperature sensor (B17/8) and pressure sensor downstream of throttle valve actuator (B28/7), engine load
- Pressure sensor upstream throttle valve actuator (B28/6)
- Crankshaft position sensor, engine speed
- Correction programming using 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 fuel injection valves.

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.