How to Predict the Piston Slap-Noise Using 3D Piston Motion Simulation

A new method for predicting the piston slap noise has been developed. Although using conventional methods, piston slap noise was estimated by using kinetic energy or the vibration of the cylinder liner using the piston secondary motion simulation, predictive accuracy was low and it lacked in reliability. In this paper the distortion of the cylinder liner at the low temperature, the dynamic stiffness of the piston and the cylinder block, and an oil film model enhancement were taken into consideration. Furthermore, comparison with the measured data of piston motions proved that prediction of a high-precision liner vibration is possible. And it proved that the relative change of the cylinder liner vibration and the subjective evaluation had high correlation with the measurement results of a real engine. As a result, piston slap noise prediction of practical sufficient accuracy was attained. From applying this method to a development engine, piston specification determination in the early stage of engine development was enabled.