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    TRIFECTA Performance

    TRIFECTA: ECM Calculated Horsepower and Torque

      For years now, GM engine controller modules (ECMs) have had the necessity to determine how much torque the engine is making, largely for drivetrain "torque management" operations. These are called torque output predictions, and they became a heck of a lot more important once GM switched to "torque based" engine management strategies (in Delphi variants, first with the E83 controller, followed by the E39, then the E78 controller used in our LUJ/LUV Cruze and Sonic vehicles) - a switch that was needed to properly support factory turbocharged engines.

    The interesting reality is these numbers are only predictions - there is no specific hardware in the powertrain that can measure ACTUAL delivered engine torque. However, the predictions are extremely accurate so long as the mathematical model behind them is correct. Initially implemented as a series of 78 three dimensional "coefficient" tables located in the ECM, they have grown to become the cornerstone of everything from idle control, to boost control, and things like the way the accelerator pedal feels in the vehicle. The end result is commanded timing, throttle blade position, and a host of other things are directly affected by how much power the engine is predicted to be making. The so-called ECM power-reported numbers are the end result of these calculations.

    These tables describe how manifold pressure, measured airflow, timing advance, and even the commanded fuel ratio affect the engine torque output under all operating conditions. As vehicles are modified away from the factory configuration, it is important to keep this model accurate by adjusting the coefficient tables.

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