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The CO2 reduction required by legislation represents a major challenge to the OEMs now and in the future. The use of fuel consumption saving potentials of friction-causing engine components can make a significant contribution. Boundary potential aspects of a combustion engine offer a good opportunity for estimating fuel consumption potentials. As a result, the focus of development is placed on components with great saving potentials. Friction investigations using the motored method are still state of the art. The disadvantages using this kind of friction measurement method are incorrect engine operating conditions like cylinder pressure, piston and liner temperatures, piston secondary movement and warm deformations which can lead to incorrect measurement results compared to a fired engine. In the past, two friction measurement methods came up, the so called floating liner method and a motored friction measurement with external charging.

The present article is concerned with the investigation of the engine noise induced by the piston slap of an actual passenger car Diesel engine. The focus is put on the coherence of piston secondary movement, impact of the piston on the cylinder liner, generated structure-borne noise excitation of the engine structure and the occurring acceleration on the engine surface. Additionally, the influence of a varying piston-pin offset and piston clearance is evaluated. The analyses are conducted using an elastohydrodynamic multi-body simulation model, taking into account geometry, stiffness and mass information of the single components as well as considering elastic and hydrodynamic behavior of the piston-liner contact. A detailed description of the simulation model will be introduced in the article. The obtained results illustrate the piston secondary motion and the related structure-borne noise on the engine surface for several piston-pin offsets and piston clearances.