Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014MRD
Engine 274.9 in model 213 (except 213.050/053/153), 238
up to model year 2021
Function requirements, general
- Engine runs
- Vehicle rolls without load request
- Not too high an exhaust temperatures
The ME-SFI [ME] control unit (N3/10) detects engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
Engine 274.9 in model 213 (except 213.050/053/153), 238 with transmission 725 up to model year 2021
The fully integrated transmission control unit (Y3/8n4) transmits information on the engaged drive range via the drive CAN (CAN C1) to the ME-SFI [ME] control unit.
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.
Inertia fuel shutoff
The overrun mode fuel shutoff is a deliberate, temporary interruption of the fuel supply, if no output is required. The overrun mode fuel shutoff basically serves for fuel economy. In the case of an active overrun mode fuel shutoff, the engine drag torque is used to decelerate the vehicle. The overrun mode 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)
The powertrain control unit (N127) directly reads in the signals of the accelerator pedal sensor and transmits these via the drive CAN to the ME-SFI [ME] control unit.
- Crankshaft Hall sensor
- Clutch pedal sensor (B53/1) (transmission 716)
The powertrain control unit directly reads in the signals of the clutch pedal sensor and transmits these via the drive CAN to the ME-SFI [ME] control unit.
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)
The fuel injectors are switched on again if the accelerator pedal is actuated or an engine torque request is pending.
Transmission 716
If the clutch pedal is actuated, the overrun mode fuel shutoff is canceled or suppressed.
After the overrun mode fuel shutoff, the ME-SFI [ME] control unit briefly enriches the fuel/air mixture in order to free the catalytic converters from 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 adjusted to a position with reduced valve overlap so that a reliable combustion without misfires can take place.
| Electrical function schematic for deceleration fuel shutoff | PE07.10-P-2714-97DBD | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MRD |