GF07.61-P-4019MIK ME-SFI Overrun Fuel Shutoff, Function

GF07.61-P-4019MIK ME-SFI Overrun Fuel Shutoff, Function
- refinement package
- as of model year 09


Function requirements for deceleration fuel shutoff, general points
^ Circuit 87M ON (engine control ON)
^ Engine running
^ Vehicle rolling
^ Accelerator not operated
^ Clutch pedal not operated (for manual transmission)
^ Selector lever position "D" or "R" (for automatic transmission)
^ Vehicle not in cruise control mode (for cruise control)
^ Not too high an exhaust temperature

Deceleration fuel shutoff, general points
Deceleration fuel shutoff in deceleration mode of the engine has the following tasks:
- Increasing the braking effect of the engine
- Reducing fuel consumption
- Improving exhaust characteristics

The ME-SFI (N3/10) control unit performs a deceleration fuel shutoff according to the following sensors and signals:
- Coolant temperature sensor (B11/4)
- Accelerator pedal sensor (B37), accelerator pedal position
- Crankshaft Hall sensor (B70), motor speed
- Clutch pedal switch (S40/3) (for manual transmission)
- Electric controller unit (VGS) (Y3/8), shift stage over the engine compartment CAN (CAN C) (for automatic transmission)

Deceleration fuel shutoff function sequence
In deceleration mode, the ME-SFI control unit shuts off the injection valves (Y62) depending on coolant temperature, selected gear and engine speed, if the accelerator pedal is not actuated.
The fuel injection valves are switched on again when the accelerator pedal is operated.

The ME-SFI control unit also adjusts the valve overlap to its minimum value using the LH and RH intake camshaft solenoids (Y49/4, Y49/5) and the LH and RH exhaust camshaft solenoids (Y49/6, Y49/7). This ensures that an optimal conversion rate of the catalytic converters is more rapidly achieved.

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

When resetting the combustion after a deceleration fuel shutoff, the ME-SFI control unit briefly shifts the firing point of the ignition coils (T1) towards "retard", in order to prevent an abrupt rise in torque.

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 (after burning). The heat so generated can overheat the catalytic converters.