Main Bearing Friction and Thermal Interaction During the Early Seconds of Cold Engine Operation

Motoring tests have been carried out on an unloaded crankshaft to examine the friction levels in main bearings and the influence of local thermal conditions, at speeds covering the range of 200–1000 rev/min and initial temperatures down to −20°C. The temperatures of the bearing oil film and adjacent metal are strongly coupled. This strongly influences the variation of friction during the early seconds of running. The possibility of reducing the thermal mass which acts as a heat sink for heat transferred has been examined. Heat conduction through the bearing shells can be reduced by raising the contact resistance at the back surface of the shells. Experimental data and model predictions show a significant reduction in initial friction levels can be achieved.