A physics-based simulation program developed by IAV is used to calibrate the torque structure and cylinder charge calculation in the electronic control unit of SI engines. The model calculates both the charge cycle and combustion phase based on flow mechanics and a fractal combustion model.
Once the air mass in the charge cycle has been computed, a fractal combustion model is used for the ongoing calculation of cylinder pressure and temperature. The progression of cylinder pressure over the high and low-pressure phases also provides information on engine torque.
Following the engine-specific calibration of the model using elemental geometric information and reduced test bench measurements, the physical engine properties can be simulated over the operating cycle. The calibrated model allows simulations to be carried out at all operating points and the results to be treated as virtual test bench measurements. The main value for the subsequent calibration of ECU functions is engine torque, which in turn depends on angular timing of spark ignition.
Besides the calibration of the ECU torque structure, the simulation model once calibrated can be used to obtain more engine-specific information such as maximum pressure and pressure increase in relation to the operating point.