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This paper shows results of an experimental study based on a passenger car diesel engine: The piston temperature reduction potential of advanced gallery cooling concepts compared to the standard gallery cooling solution has been investigated. Therefore, different piston cooling concepts featuring one or two oil nozzles per cylinder and combined with compatibly designed cooling galleries have been tested. The influence of the parameters cooling gallery shape and oil nozzle configuration relative to the piston on the piston temperature has been analyzed. The use of suitably adapted advanced piston cooling concepts results in significant improvement of cooling efficiency compared to the established gallery cooling solution.

Optical investigations using optical fibres were carried out in the first available direct injection SI-engine, the Mitsubishi GDI, in the driving mode. The optical access to the combustion chamber was realized by 8 optical sensors evenly distributed in a ring on the ground electrode of the standard spark plug. All investigations, steady state (constant load and velocity) and unsteady state (engine starts), show, that there is preferred flame propagation to the intake valves, caused by a reverse tumble in-cylinder flow. As the inflammation depends on thermodynamic conditions, flow characteristics and the actual air/fuel-ratio at the spark plug, the optical sensors can be used to describe the quality of stratification.