Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014MNF
Engine 176.9 in model 463
as of model year 2016 up to model year 2019
Function requirements for overrun mode 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 relay 87M(F58kN) is switched on for circuit 15 ON. The fully integrated transmission control unit (Y3/8n4) transmits the status of the gear range via drive CAN (CAN C) to the ME-SFI [ME] control unit (N3/10).
Overrun mode fuel shutoff, general
Overrun mode fuel shutoff in overrun mode of the engine has the following tasks:
- increasing the braking effect of the engine.
- reducing fuel consumption.
- improving exhaust characteristics.
The ME-SFI [ME] control unit performs a overrun mode 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 speed
Overrun mode fuel shutoff, function sequence
Y76In overrun mode, the ME-SFI [ME] 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 fuel injectors for cylinders 1 to 8 are switched on again when the accelerator pedal is operated.
The ME-SFI [ME] 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 overrun mode fuel shutoff, the ME-SFI [ME] 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 overrun mode fuel shutoff, the ME-SFI [ME] control unit temporarily adjusts the ignition angles of the ignition coil for cylinders 1 + 2 to cylinders 7 + 8 (T4 to T4/3) in the "retard" direction.
Overrun mode fuel shutoff is disabled when exhaust temperatures are too high, since the high oxygen content occurring in the exhaust during a overrun mode 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 overrun mode fuel shutoff | PE07.10-P-2714-97ZGD | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNF |