Piston slap is one of the major sources of noise in a 4-cycle diesel engine. Piston slap is not only one of major sources of noise, but also a source of deterioration of engine performance, i.e. liner cavitation erosion, piston-liner wear, oil consumption and piston assembly friction.
Piston slap motion was measured from a 4-stroke IDI diesel engine by means of eddy current type gap sensors mounted near the top and bottom of the piston thrust and anti-thrust skirts. Effect of engine speed, load, coolant temperature and oil viscosity on piston motion was investigated.
The measured piston motion showed 6 slaps per cycle resulting from the change of side force. Major piston slap timing was retarded as engine speeds became higher. The increase of engine load made large piston transverse movement toward thrust side of cylinder block. Piston transverse movement was reduced as a result of higher coolant temperature due to reduced piston-liner clearance.
