Within the research project SIDYN the operating behavior of an electric power generator in an isolated, dynamically loaded grid is to be described and predicted by using simulation approaches. The stage of development shown in this paper includes a coupled thermodynamic/mechanic engine model, which has to be extended by a mechanic/electrical generator-grid-model in the course of the project. For verification of the engine simulation, model measurements were carried out at the engine test bed at Wismar University. One of the key measures to enable simulations of different load scenarios and its impact on the system is the precise de1nition of subsystem interfaces. To do so, an approach described in  is implemented into MATLAB Simulink. To characterize the controlling behavior of the industrial engine the interfaces between the transient torque and angular velocity of the drive train were observed. Considering the existing experimental setup, it can be concluded that good results could be achieved with the present model. The calculated and simulated cylinder pressure curves show a high level of agreement at various stationary operating points. However, to strive for the calculation of transient operation behaviors, the model as well as the engine test bed require further extension.