A fast calibration tool for the tuning of zero-dimensional combustion models has been developed and assessed on a 1.6 L Euro 6 GM diesel engine. The tool is capable of identifying the optimal set of model tuning parameters on the basis of a few combustion metrics related to heat release, as well as of peak firing pressure and indicated mean effective pressure.The method has been assessed and validated for a real-time zero dimensional combustion model previously developed by the authors. A detailed comparison has been made between the conventional and the newly proposed calibration procedures, at both steady-state and transient-state conditions.