Friction Characteristics of Steel Pistons for Diesel Engines

The use of iron pistons is increasing due to the higher power requirements of diesel truck engines. Expansion of the iron piston is a common concern. The purpose of this study is to clarify the lubrication conditions of cast iron and steel pistons. Friction of steel and cast iron pistons were measured using the floating liner method. The friction of conventional aluminum pistons was also measured for comparison in this study. The measurement of the secondary motion of each piston was carried out to analyse piston friction, and the following findings were obtained. The cast iron piston showed boundary lubrication at compression top dead center (TDC). This is presumably caused by the larger tilting angle of the piston induced by the larger piston clearance. Steel pistons showed hydrodynamic lubrication conditions at TDC and BDC through each cycle, due to a good oil supply.