Diesel engines with direct injection have become very important in recent years. Because of flexible injection curves, the energy conversion can be manipulated during operation. To examine how the pressure inside the combustion chamber is influenced new engine models are necessary. The engine model introduced in this paper can be used in the development process of engine control units and as a state observer for sophisticated controllers during on-board operation of the car. This paper provides a brief introduction into the model, indicating problems and solutions involved in realtime calculation.