Design, implementation, and operation of controllers for Diesel engines made great progress in recent years. Nevertheless they could be more efficient if the advanced techniques of modern control theory were applied to them.The efficiency of the most conventional controllers is limited by two major facts: firstly, that they have a fixed structure with constant parameters over the whole operating field of the engine and secondly, that they are designed using a single transfer function of the system that is obtained by linearization at one operating point.Most recent developments using microcomputers allow an easy adjustment of the control strategy to the operating conditions of the engine. Furthermore they allow the control of a multivariable system as is encountered, when the injection and the turbocharger of an engine is controlled simultaneously. This is only possible when a sufficiently large on-line computer capability is available.For such a controller design a mathematical model of the controlled engine, which represents the dynamic behaviour of the combined system of engine plus turbocharger, needs to be available. This model serves as a tool for the system simulation which again supports the controller design with respect to the optimization of the controller. The used model needs to be sufficiently accurate. In addition to this, a simple model that can be simulated in real time to support the controller operation is required.The final goal of the overall design procedure is a controller that provides a compromise between a low price on the one side and high achievements concerning the computer power including the used sensors, actuators, etc... associated with easy maintenance.According to this optimization a strategy is presented which results is a modern adaptive controller for Diesel engines. Furthermore a control concept for a turbo charger is presented which allows an optimal operation of the entire engine including the turbo charger set. This control concept improves, once being implemented on a computer, the overall system performance under all operating conditions.