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A thermodynamic methodology of TDC determination in IC engines based on a motoring pressure-time diagram is presented. This method consists in entropy calculation and temperature-entropy diagram analysis. When the TDC position is well calibrated, compression and expansion strokes under motoring conditions are symmetrical with respect to the peak temperature in the (T,S) diagram. Moreover, in case of error on the TDC position, a loop appears, which has no thermodynamic significance. Hence, an easy methodology has been conceived to obtain the actual position of TDC. This methodology is applied to motoring measurements in order to present its performance, which are compared to usual methods.

In this paper, a generic methodology is proposed to simulate the static and dynamic responses of a SI gas engine. The predicted simulation of engine performances is based on a one zone thermodynamic model. The turbocharger is modeled by using polytropic coefficients, the intercooler by its efficiency. The Ventury effect carburetor model is based on physic properties and the butterfly valve model uses a classical approach. A comparison between the simulation and experimental results is realized in terms of static and dynamic performances in closed loop. Comparisons with actual data obtained on a 210 kW engine shows that the maximum error is less than 5 %.