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

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







Deceleration fuel shutoff has the following tasks:
- Increasing the braking power of the engine in the overrun mode
- Reducing fuel consumption
- Improve exhaust characteristics in overrun

In overrun mode, the ME-SFI [ME] control unit switches off the fuel injection valves depending on the coolant temperature and engaged gear, if:
- Accelerator pedal is not operated (detection on the basis of actual value signals from the accelerator pedal sensor)
- Vehicle not in Cruise control/Distronic mode

The fuel injection valves are switched on again when the accelerator pedal is operated.

In order to prevent a sudden torque rise when combustion is reestablished after deceleration fuel shutoff, ignition timings are briefly adjusted towards "retarded".

After overrun mode the mixture is enriched for a short time in order to free up the catalytic converters from the increased oxygen. The valve overlap is also set to its minimum value by the camshaft adjustment. This ensures that an optimal exhaust conversion rate is more rapidly achieved.

The engine speed on reestablishment of combustion is dependent on the coolant temperature, the engine and transmission design and the engaged drive position.

The overrun fuel shutoff is locked out for drive position "P" or "N" and for excessively high exhaust gas temperatures.

The high oxygen content in the exhaust gas for overrun fuel shutoff leads to increased oxidation of carbon monoxide and hydrocarbon (afterburning). The heat so generated can overheat the catalytic converters.