Decel
The Decel function disables the injectors under deceleration conditions to save fuel, improve emissions, and give smoother engine operation.
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Decel Detection Tab
Mode
Selects the load sensor that will be used to activate the Decel Cut. (Default = TPS)
TPS
The Throttle Position Sensor will be used for the activation load. The TPS must be below the User Demand Minimum value to cause activation. Exceeding this amount of TPS will resume normal engine operation.
MAP
The Manifold Absolute Pressure sensor will be used for the activation load. Selecting MAP will activate the Max MAP setting.
Max MAP
The MAP must be below this amount to activate the Decel Cut. Exceeding this amount of MAP will resume normal engine operation. (Default = -80kPa)
Decel Cut Tab
Enable Decel Cut
Enables the Decel Cut, and activates the Cut Delay Time table in the ECU Navigator
Ignition Retard
When the Decel Cut is active the ignition timing will be retarded by this amount. This is to improve the smoothness of the transition back to normal engine operation. This amount of ignition retard will be fed in over a 500ms period before cutting fuel. If the Delay Time is less than 500ms then this time is shortened to match. (Default = 10)
Fuel Enrichment
When normal engine operation is resumed, the first pulse of fuel will be enriched by this amount. This is to help wet valves and port walls after running dry for a period of time. Without this enrichment there may be a lean condition when normal injector operation resumes. (Default = 25)
Cut Activation Offset
For the Decel Cut function to activate, the RPM must exceed the Min RPM table value by this amount. This is to provide a hysteresis to prevent repeated cut operations if the RPM is close to the amount in Min RPM table. (Default = 400)
Post Start Delay
The Decel Cut function is prevented from activating for this amount of time after the engine has started. This is to prevent initial startup RPM flaring and Post Start Idle Offset from activating the Decel Cut function. (Default = 5)
A/C Offset
Increases your Decel Min RPM by this value when A/C Output is active. If you don't want your Decel min RPM to change when A/C turns on, set this value of 0.
Min Gear
Allows the user to set a minimum gear, whereby Decel Cut will not be active below this gear. (Reverse = -1). If you don't want the gear to have an effect, set to -3. This is to prevent poor drivability in the lower gears and is typically set to 2 or 3.
Min Vehicle Speed
Decel Cut will not be active below this speed. If you don't want vehicle speed to have an effect, set to 0. This is to prevent decel fuel cut from activating when stationary.
Min Coolant Temp
Decel Cut will not be active below this coolant temperature. This setting is to prevent decel fuel cut from activating with a cold engine resulting in poor drivability. If you don't want coolant temp to have an effect, set to a value below normal cold start temperatures.
Arming TPS
Decel Cut will not arm until this amount of throttle position has been exceeded. It will then activate when Zero Demand conditions are met. This is to prevent oscillation around the zero demand conditions. If you don't want throttle position to have an effect, set to 0. Typically values are around 1 to 5%.
Related Tables
Min RPM
When the Decel Cut function has activated, normal engine operation will occur if the RPM drops below the amount in this table. Up to 3D mapping is available.
Note: RPM Derivative (rate) is used to detect how fast the RPM is falling. If at a slow rate the Decel Cut can continue to a lower RPM for smoother transition. If at a fast rate, such as free-revving, the Decel Cut will resume normal engine operation at a higher RPM value to give a smoother transition.
O2 Control also uses this table to disable closed loop above this RPM when Zero Demand conditions are met to prevent the ECU from trying to adjust the fuel when combustion is not stable.
Cut Delay Time
This is the amount of time between meeting the Decel Fuel Cut conditions and when the fuel is actually cut. A small amount of time is usually needed to smooth the entry into the cut condition. At higher RPM a longer delay allows time for gear changes to occur before cutting. Typically around 200 to 500ms at low rpm and around 2500 to 3000ms at high rpm.
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