Deceleration fuel shutoff, function - GF07.10-P-1014MMO

ENGINE 276.9 in MODEL 212.095 up to model year 2014 

The partial function "deceleration fuel shutoff function" is viewed and described from the view of the engine timing for the internal combustion engine.

The deceleration fuel shutoff of the internal combustion engine is primarily activated at speeds > 160 km/h.

For speed < 160 km/h the internal combustion engine is usually disconnected from the drive through opening of the wet clutch and switched off since this is the most effective from an energy point of view.

If a greater deceleration is to be realized by the drive than the electrical machine (A79/1) is capable of providing, then the deceleration fuel shutoff is also active under 160 km/h.

Further information about the function sequence in the driving condition decel mode from the point of view of the hybrid system is described in the following document:

• Driving, function 

Function requirements for deceleration fuel shutoff, general points 

• Hybrid system "READY" (green or yellow)
• Accelerator pedal not operated
• Internal combustion engine running
• Vehicle speed > 160 km/h or < 160 km/h and no regenerative braking possible
• Gear range "D"
• Not too high an exhaust temperature

The function requirements "internal combustion engine running" includes all function sequences of the fuel low pressure and high-pressure circuit, as described in the function "fuel supply".

Deceleration fuel shutoff, general 

Deceleration fuel shutoff in deceleration mode of the internal combustion engine has the following tasks:

• Increasing the braking effect of the engine
• Reducing fuel consumption
• Improving exhaust characteristics

The ME-SFI [ME] control unit (N3/10) performs a deceleration fuel shutoff depending on the following sensors and signals:

• Coolant temperature sensor (B11/4)
• Accelerator pedal sensor (B37), accelerator pedal position
• Crankshaft Hall sensor (B70), engine speed
• Fully integrated transmission control unit (Y3/8n4), gear range over drive train CAN (CAN C)

Deceleration fuel shutoff, function sequence 

In deceleration mode, the ME-SFI [ME] control unit switches off the fuel injectors (Y76) depending on coolant temperature, selected gear and engine speed, if the accelerator pedal is not actuated.

The fuel injectors are switched on again when the accelerator pedal is operated.

The ME-SFI [ME] control unit also actuates the LH and RH intake camshaft solenoids (Y49/4, Y49/5) and the LH and RH exhaust camshaft solenoids (Y49/6, Y49/7) to adjust the camshafts into a position with reduced valve overlap. This allows secure combustion without misfires.

After deceleration fuel shutoff, the ME-SFI [ME] control unit enriches the fuel-air mixture by briefly extending the injection time, in order to protect of the catalytic converters from enriched oxygen.

In order to prevent a sudden rise in torque when combustion is restarted after a deceleration fuel shutoff, the ME-SFI [ME] control unit briefly shifts the ignition angles of the ignition coils (T1) towards "retard".

Deceleration fuel shutoff is disabled when exhaust temperatures are too high, since the high oxygen content occurring in the exhaust during a deceleration fuel shutoff could cause increased oxidation of carbon monoxide and hydrocarbon (afterburning). The heat so generated can overheat the catalytic converters.

	Electrical function schematic for deceleration fuel shutoff		PE07.10-P-2714-97DAI
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MMO