Regarding driving units with combustion engines, it is primarily the torsional vibrations caused by the unsymetrical gas forces, inertial forces and out-of-balance. forces which may cause harm to the driveline. The program DRESP was developed at the Institute of Machine Elements and Machine Design (IME) of the RWTH Aachen in order to simulate such nonlinear torsional vibration systems. The program has been established as an efficient simulation tool in numerous companies for driveline analysis. Fourier series of gas pressure moments are used for the simulation of torsional vibrations in order to simulate the periodic excitation of combustion engines. But this is only applicable at a certain stationary operation point of the engine. To avoid this disadvantage, a simulation model based on a combustion process calculation can be used instead. It computes the gas and mass excitation forces by modeling the combustion process and the kinematic of the crank drive for every cylinder. The theoretical basis is the so called One Zone Model according to Vibe which is a simplified thermodynamic model of the cylinder. The presentation shows a DRESP-simulation using the example of a modern marine drive with a two-stroke diesel engine. It shows the dynamic behavior of the powertrain during an engine-startup process from zero to nominal speed. The simulation of a complete driving cycle including start-up processes and load fluctua~ tions is difficult to realize. The cylinder pressure results from a simplified calculation of the combustion process based on the One Zone Model. The fuel conversion is included by so called Vibe-functions, which are able to characterize the combustion process. The excitation torque at the crankshaft results in consideration of the cylinder pressure and the geometrical data of the crankshaft as well as the mass excitation forces. This computational method takes the interaction between the combustion process and the driveline in consideration and offers the possibility to simulate transient conditions with fluctuating speed and load. The program DRESP first-time transfers this concept in the area of torsional vibration simulation. The presented example of the start-up process of a two-stroke diesel engine shows a good correspondence between the measured and calculated engine speeds. It offers a detailed overview about the dynamic loads in the power-train as well as their analvsis. The model still has limitations regarding the turbo-charging and charge air cooling. Currently these effects are only included by measured pressure distributions. A simulation of the dynamic, behavior of these components may be realized by an extension of the existing control structure.