Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Function requirements, general
- Engine runs
- Vehicle rolling without load requirement
- Not too high an exhaust temperatures
The fully integrated transmission control unit (Y3/8n4) transmits information about the engaged gear range via the drive train CAN (CAN C1) to the ME-SFI [ME] control unit (N3/10).
The ME-SFI [ME] control unit does not receive any engine torque request via the drive train CAN, powertrain control unit (N127) and chassis FlexRay (Flex E).
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 generated here can overheat the catalytic converters.
Deceleration fuel shutoff
The deceleration fuel shutoff is an intended, temporary interruption to the flow of fuel, once there is no output required. The deceleration fuel shutoff is largely intended for saving fuel. With an active deceleration fuel shutoff, the engine drag torque is used to decelerate the vehicle (engine brake). The deceleration fuel shutoff is active above the idle speed.
The ME-SFI [ME] control unit evaluates the signals of the following sensors for implementing the deceleration fuel shutoff:
- Coolant temperature sensor (B11/4)
- Accelerator pedal sensor (B37)
- Crankshaft Hall sensor (B70)
The ME-SFI [ME] control unit stops injection by no longer actuating the following components:
- Cylinder 1 fuel injector (Y76/1)
- Cylinder 2 fuel injector (Y76/2)
- Cylinder 3 fuel injector (Y76/3)
- Cylinder 4 fuel injector (Y76/4)
- Cylinder 5 fuel injector (Y76/5)
- Cylinder 6 fuel injector (Y76/6)
- Cylinder 7 fuel injector (Y76/7)
- Cylinder 8 fuel injector (Y76/8)
The fuel injectors are switched on again when the accelerator pedal is operated or an engine torque request has been made.
After deceleration fuel shutoff, the ME-SFI [ME] control unit briefly enriches the fuel/air mixture in order to relieve the catalytic converters of enriched oxygen.
In order to prevent the engine torque from increasing abruptly when combustion resumes after the deceleration fuel shutoff, the ME-SFI [ME] control unit adjusts the ignition in the "retarded" direction. The camshafts are set to a position with reduced valve overlap to ensure a safe combustion without misfires.
| Electrical function schematic for deceleration fuel shutoff | Engine 177.9 in model 205, 253 | PE07.10-P-2714-97FBD | |
| Engine 177.9 in model 213 up to model year 2021 | PE07.10-P-2714-97DBG | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 177.9 in model 205, 253 | GF07.70-P-9998MNA | |
| Engine 177.9 in model 213 up to model year 2021 | GF07.70-P-9998MNE |