Start, post-start phase and warm-up enrichment, function

GF07.10-S-1007D

Start, post-start phase and warm-up enrichment, function

4.9.15

Engine

200.7 in model 415

Function requirements for starting, the post-start phase and warm-up enrichment, general points

 Terminal 87 (engine management) ON

 Engine runs

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.

Function sequence for start phase, post-start phase and warm-up enrichment

The function sequence is divided into the following subfunctions:

 Function sequence for starting mixture enrichment

 Function sequence for post-start enrichment

 Function sequence for warm-up enrichment

Function sequence for 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 [ME] control unit (N3/10) calculates the injection duration for start enrichment on the basis of the signals from the following sensors:

 Coolant temperature sensor (B11/4), coolant temperature

 Crankshaft Hall sensor (B70), engine rpm

 Ignition lock switch (S2), terminal 50 signal over interior CAN (CAN I) to the Safety Relay Module (SRM) control unit (N50)

The ME-SFI [ME] control unit (N3/10) upon receipt of the terminal 50 signal from the ignition lock switch (S2) extends the injection duration of the fuel injectors (Y76).

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 (N3/10).

 No further engine start is possible below an on-board electrical system voltage of approx. 7 V.

Function sequence for post-start enrichment

After cold start, the fuel-air mixture is further enriched.

Enleanment due to the fuel condensating on the still cold cylinder surfaces is compensated by the post-start enrichment.

The ME-SFI [ME] control unit (N3/10) calculates the injection duration of the fuel injectors (Y76) for the post-start enrichment on the basis of the coolant temperature at start and the number of combustion cycles since the start.

An additional fuel quantity is metered to the engine by the ME-SFI [ME] control unit (N310) in line with the characteristics map.

Function sequence for warm-up enrichment

After start and post-start enrichment, the fuel-air mixture is further enriched via the warm-up enrichment in order to ensure rapid warm-up.

The ME-SFI [ME] control unit (N3/10) calculates the injection duration of the fuel injectors (Y76) for warm-up enrichment on the basis of the signals from the following sensors:

 Intake camshaft Hall sensor (B6/15), intake camshaft setting

 Exhaust camshaft Hall sensor (B6/16), exhaust camshaft setting

 Coolant temperature sensor (B11/4), coolant temperature

 Temperature sensor downstream of charge air cooler (B17/8), charge air temperature

 Intake manifold pressure sensor (B28/15)

 Crankshaft Hall sensor (B70), engine rpm

 Correction programming using Xentry diagnostics

An additional quantity of fuel is metered to the engine in line with the performance map. To this end, the ME-SFI [ME] control unit (N3/10) increases the injection duration of the fuel injectors (Y76). It will also take into account any correction programming that may have been made.

The ignition timing of the ignition coils of cylinders 1 to 4 (T1/1 to T1/4) are determined by their own characteristics map during warm-up.

Via the intake camshaft actuator solenoid (Y49/4) and the exhaust camshaft actuator solenoid (Y49/5), the ME-SFI [ME] control unit (N3/10) determines the internal exhaust gas recirculation based on 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 near idling range, the injection duration depends primarily on the coolant temperature; under partial and full load, the load requirement is the decisive factor.

Once enabled, the lambda control monitors the injection period.

	Electrical function schematic for start phase, post-start phase and warm-up enrichment		PE07.10-S-2707-97D
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-S-9998D