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Advanced thermal management systems in passenger cars present a possibility to increase efficiency of current and future vehicles. However, a vehicle integrated thermal management of the combustion engine is essential to optimize the overall thermal system. This paper shows results of an experimental heat flux analysis of a state-of-the-art automotive diesel engine with common rail injection, map-controlled thermostat and split cooling system. Measurements on a climatic chamber engine test bench were performed to investigate heat fluxes and energy balance in steady-state operation and during engine warm-up from different engine start temperatures. The analysis includes the influence of the operating point and operating parameters like EGR rate, injection strategy and coolant temperature on the engine energy balance.

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.