Friction Teardown Data From Motored Engine Tests on Light Duty Automotive Diesel Engines at Low Temperatures and Speeds

Friction data have been acquired from motored engine tests on four designs of light duty automotive diesel engines. The engines were all four-cylinder designs with a swept capacity around two litres (1.8l-2.2l). These are typically used in the small and medium car sectors of the European market. The test programme was aligned to cold start and warm-up conditions. The data cover temperatures at the start of motoring of −20°C and above, and motoring speeds covering 200 rev/min – 1000 rev/min. Most tests were carried out using 10W/30 oil. The breakdowns separated piston assembly, crankshaft assembly, valve train and auxiliary component contributions to friction mean effective pressure (fmep), from −20°C upwards, under quasi-steady thermal conditions. Under these conditions, during warm-up the variation of engine fmep exhibits a simple power law dependence on oil viscosity evaluated at the current bulk oil temperature. The dependence of component contributions on oil viscosity has been examined. The empirical coefficients and functions used in the engine friction model developed by Patton, Nitschke and Heywood (SAE 890836) have been modified to give an improved fit to the low speed, low temperature test data, whilst limiting the effect on predictions for fully-warm conditions. The quality of the predictions is illustrated. The degree to which the effect of design detail can be predicted and the scope to reduce friction levels through design are discussed.