Note: Refer HERE for an explanation of Overrun Fuel Cut and a Setup Example.
The following settings allow the overrun fuel cut to be tailored to the application.
Turn the Overrun Fuel Cut function ON or OFF.
The level the throttle position (TP(Main)) must be below before the overrun fuel cut is applied (if other activation conditions are met). If an Ethrottle is used the accelerator position (AP(Main)) value will be used instead of the throttle position (TP(Main)) value. If Cruise Control is used a combination of accelerator position (AP(Main)) and throttle position (TP(Main)) will be used.
The level is generally set slightly above the closed throttle (or accelerator) point to allow for some noise which is inherent in the signal from TPS or APS, a typical value is 1%.
This will delay the Overrun Fuel Cut from activating for a short length of time after the required conditions are met, the time units are in seconds. This feature can be used to prevent an overrun fuel cut occurring during gear shifts.
Torque Reduction/Introduction Time
This is the amount of time it takes for Overrun Fuel Cut's Ignition Retard to be fully applied. It is also the amount of time it takes for the Ignition Retard to return to zero after an Over-run Fuel Cut.
To help smooth the transition as the fuel cut turns on and off, the ECU will progressively retard the ignition timing prior to cutting fuel and progressively advanced back to normal after the fuel has been restored. Changing the Ignition Retard adjusts the full amount of ignition retard the ECU will use, the amount of time taken to introduce and remove the ignition retard is controlled by the Torque Reduction/Introduction Time setting.
Overrun De-Activation RPM Table
The level the engine speed must be above before the overrun fuel cut is applied (if other activation conditions are met).
The De-Activation RPM must be set above the engines idle speed so that fuel is not cut when the engine is sitting at idle with the throttle closed, in practise the value should be set around 500 RPM above idle so that as the engine speed falls during overrun the fuel is turned back on early enough to stop the engine from stalling. A typical value for a fully warm engine (80-100 degrees C) is 1500 RPM.
When the engine is cold the idle speed control system will typically be setup to raise the idle speed,because of this it is necessary to raise the De-Activation RPM at lower engine coolant temperatures. Even if the idle speed is not increased during cold running it is still advisable to use larger numbers at lower engine coolant temperatures, this is because cold engines generally do not tolerate the use of a fuel cut especially at low engine speed.