GF07.61-P-4019M ME-SFI Overrun Fuel Shutoff, Function

GF07.61-P-4019M ME-SFI Overrun Fuel Shutoff, Function

Component Identification:

Overrun fuel shutoff has the following tasks:
^ Increases engine braking effect in overrun mode
^ Reduces fuel consumption
^ Improves exhaust characteristics in overrun mode.

In overrun mode, the ME-SFI control unit switches off the fuel injection valves in line with the coolant temperature and the gear selected, provided that the accelerator pedal is not depressed (detected via actual value signal from pedal value sensor).
The fuel injection valves are switched back on when the accelerator pedal is depressed.
Overrun fuel shutoff is suppressed at excessively high exhaust gas temperatures since the high oxygen content in the exhaust gas during this process can lead to increased oxidation of carbon monoxide and hydrocarbon (after burning). This can result in additional heat (thermal reaction) that may overheat the catalytic converters.

Following overrun mode, the mixture is enriched briefly to eliminate the enriched oxygen generated during overrun mode from the three way catalytic converters. This ensures that an optimal conversion rate is more rapidly achieved.

To prevent a sudden torque rise when combustion is reestablished following overrun fuel shutoff, ignition timing is adjusted briefly to "retarded".

Rotational speed and coolant temperature are dependent on the engine and transmission version (different performance maps).