The high performance of dynamical engine test benches allows a great degree of freedom in the structure of engine testing which represents a substantial contribution to decrease development times of vehicles and is correspondingly quietly often used. However, there are physical conditions which limit this degree of freedom. The exploitation of those limits from control point of view, as well as understanding of their effects on the planning of experiments, has been analysed in a cooperation of the Institute for Design and Control of mechatronical Systems at the JKU Linz, the Linz Center of Mechatronics (LCM) and AVL Graz.