GF07.10-P-1014MI Deceleration Fuel Shutoff Function

GF07.10-P-1014MI Deceleration Fuel Shutoff Function
- 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
^ Selector lever position "D" or "R" (for automatic transmission)
^ Vehicle not in cruise control or Distronic Plus mode (if Distronic PLUS installed)
^ 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), engine speed
- Clutch pedal switch (S40/3) (for manual transmission)
- Fully integrated transmission control controller unit (Y3/8), stage via the drive train CAN (CAN C) (for an automatic transmission)

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

If the clutch pedal is actuated for a manual transmission the deceleration fuel shutoff is broken off or suppressed.

The ME-SFI [ME] control unit also the valve overlap to its minimum value via 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 [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 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 (after burning). The heat so generated can overheat of the catalytic converters.