GM > Engine > Torque Management > Engine Torque

**Engine Torque Model**

The PCM uses a airflow, fuel and thermal efficiency and heat based
model of torque.

__Inertia Factor:__This is an engine inertia factor that is used to estimate torque required to accelerate/decelerate the engine.__Fuel Qc Factor:__This is the constant used to represent the Heat Of Combustion (Qc) in the torque model.__MBT Torque Filter:__This is the filter coefficient used to filter the calculated Mean Best Torque (MBT).__Transfer Case Ratio:__Transfer case ratio used in 4WD applications to calculate torque values when in 4WD low range.__Accessory Torque:__This is the model of accessory torque load on the engine (excluding AC compressor when engaged).__Friction Torque:__This is the model of friction torque loss within the engine.__Friction Torque Multiplier:__This is a multiplier on the friction torque value at various oil temperatures.

**AC Compressor Torque**

The AC compressor places a large and variable load on the engine
when engaged. The PCM has a complex model of AC Torque load
including inertia effects and ramp in/out when the AC clutch first
engages. The AC torque calculation is also used to calculate the
Idle AC Airflow compensation for IAC/ETC control during idle.

__Torque vs. AC Pressure:__This is the torque loss of the AC compressor versus AC Pressure.__Torque vs. IAT:__This is the increase in AC torque loss due to inlet air temperature.__Inertia Torque:__This is the model of inertia torque load for the AC clutch when it engages.__On Hold Time:__Time to hold Inertia Torque before ramp out begins when AC clutch first engages.__Inertia Torque Airflow Ramp:__This controls the ramp out rate of AC inertia torque once the On Hold Time expires.__Off Hold Time:__Time to hold AC torque before decaying to zero when AC clutch is disengaged.__Torque Reduction:__Maximum amount of torque reduction that the AC can request.

**AC Bump Torque**

This is the transient model of AC torque load when the AC clutch
engages and disengages.

__Delay:__Time delay between commanding the AC on and the compressor loading up the engine.__Ramp In:__Ramp in rate for AC Compressor torque.__Ramp Out:__Ramp out rate for AC Compressor torque.__Duration Max:__Maximum duration for transient torque model ramp out. After this time AC torque will be set to zero when AC disengages.__Reset Limit:__If AC torque loss delta is less than this the adaptive idle cells will be reset to zero.__ETC% Max:__Maximum amount of extra ETC throttle position the AC airflow can command.__On Delay:__Delay before retarding spark when the AC engages.__Off Delay:__Delay before retarding spark when the AC disengages.__max Spark Retard:__Maximum spark retard the AC transient can request.__Spark Off Delay:__Delay before ramping spark out when the AC disengages. After Off Hold Time expires.

**Delivered Torque PWM**

The delivered torque PWM is used in various applications. eg. for
some Holden vehicles it is used to control the fuel pump
voltage.

__Stall:__commanded PWM % when stall protect is activated.__Shift In Progress:__commanded PWM % when a shift is in progress.__Normal Minimum:__Minimum allowed PWM %__Minimum Factor:__Factor used to calculate PWM minimum PWM %.__Fail Condition:__PWM % applied to when torque management failure conditions are detected.

**Stall Protect**

__Enable RPM:__If RPM drops below this them Stall Protect PWM % will be commanded.__Delta Gain:__Used for calculating RPM derivative factor to determine if engine stall is likely.__Disable Factor - Hi:__If RPM derivative factor is above this multiplied by current Desired Idle RPM then stall protect will disable (if enabled).__Disable Factor - Lo:__If RPM derivative factor is below this multiplied by current Desired Idle RPM then stall protect will disable (if enabled).