This paper will describe an approach method for the complete modelling of an engine; our approach provide software for very detailed description (Knowledge model) as well as simple models (Representation model) which can be implemented in a governor to improve consistently the system behaviour.The software for very detailed description require performing workstation (SUN: Californian Computer Manufacterer; etc., …) and the simple models can be used in real time on the latest microprocessors.We will describe here essentially the knowledge model part of this research.As they offer a similar approach to all types of systems, Bond graphs are a tool of great interest for knowledge modelling. This tool has a limited expansion in Europe and even more so in the industrial area. We have used this technique to modelise and simulate the behaviour of a turbocharged six cylinder (mid-range) Diesel engine.The program handles the various non-linearities, the various coolants, the heat transfers within the cylinder head and the ignition delays.During the simulated running, the engine is controlled by a governor which may be chosen by the operator in an array ranging from the simplest PID (Proportional, Integral, Derivative Governor) to the most modern and performing algorithm. This program can be used for Component Design and Analysis and for the Design of New Control algorithms.The program can be quickly adapted to simulate any other Diesel engine. In the following pages, we shall introduce the program, its structure as well as the quite attractive First results.