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Presented within the framework of this SAE Technical Paper are the highly accurate results of friction experiments, performed upon a floating-liner, single-cylinder test engine with a capacity 0.5 liters and crank angle resolution during motored and fired operation. This allows for the measurement of mixed friction zones at the dead centers. These mixed friction zones can result in friction losses and lead to wear in the components in-volved. The strength of the friction forces in any given mixed friction zone is largely dependent on the operating point. This is why the influence of each of the most important operating parameters - speed (rpm), load, oil and coolant temperature - is individually analysed, before the interactions, which are depicted in the resultant engine map, are discussed.

This SAE Technical Paper will give a summary of the detailed results of crank-angle-resolved friction measurements which were carried out in motored and pressureless operation on a floating liner single cylinder test engine with a displacement of 0.5 liters. Friction forces that occur during running-in are introduced and discussed with regard to mixed friction and hydrodynamic friction for different oil control rings. Three different ring pre-loads are examined using constant geometries. In a second test series, the outer contour and coating is varied while the pre-load stays constant.

This SAE Technical Paper gives a summary of the essential findings in the development and operation of a test engine dedicated to the measuring of the friction between the piston group and the liner. Firstly the fundamental demands on the high-precision and close to real engine operation friction measuring are laid out. Subsequently the basic engine, the measuring system based on the floating liner method including a gas balance device, as well as the implemented measuring technique are specified. Major influencing variables on the friction of the piston assembly and its interference variables are also summarized. Extensive information about the systematic and strategies for the test engine's operation startup are given in acknowledgement of influencing and interference variables. This strategy reduces the developmental and startup process of an engine dedicated to the measuring of piston group friction.