Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014MNH
Engine 176.9, 177.9 in model 463
as of model year 2019
Function requirements for deceleration fuel shutoff, general points
- Circuit 87M (Engine management ON)
- Engine runs
- Accelerator not operated
- Gear range "D" or "R" is engaged
- Vehicle is not in cruise control mode
- Not too high an exhaust temperatures
The circuit relay87M (K40/8 kN) is switched on for circuit 15 ON. The fully integrated transmission control unit (Y3/8n4) transmits the status of the drive range via drive CAN (CAN C1) to the ME-SFI control unit (N3/10).
Deceleration fuel shutoff, general
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 control unit performs a deceleration fuel shutoff dependent on signals from the following sensors:
- Coolant temperature sensor (B11/4), coolant temperature
- Accelerator pedal sensor (B37), accelerator pedal position
- Crankshaft Hall sensor (B70), engine rpm
Deceleration fuel shutoff, function sequence
Y76In deceleration mode, the ME-SFI control unit switches off the fuel injectors for cylinders 1 to 8 (/1 to Y76/8) dependent on coolant temperature, engaged gear and engine speed, if the accelerator pedal is not actuated. The cylinders 1 to 8 fuel injectors are switched on again when the accelerator pedal is operated.
The ME-SFI control unit also adjusts the camshafts using the left intake camshaft solenoid (Y49/4), the right intake camshaft solenoid (Y49/5), the left exhaust camshaft solenoid (Y49/6) and the right exhaust camshaft solenoid (Y49/7) to adjust the camshafts to a position with reduced valve overlap.
After deceleration fuel shutoff, the ME-SFI control unit enriches the fuel/air mixture by briefly lengthening the injection period in order to relieve the catalytic converters of enriched oxygen.
To prevent an abrupt torque increase when combustion restarts after deceleration fuel shutoff, the ME-SFI control unit temporarily adjusts the ignition angles of the ignition coils for cylinders 1 + 2 to cylinders 7 +8 (T4 to T4/3) in the "retard" direction.
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-2714-97ZGF | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNH |