Experimental Investigation of Influence of Piston Pin-Offset on Reduction of Piston Slap Noise

Piston slap is the primary source of noise and vibration in an Internal Combustion Engine. In this work, an experimental study of influence of piston pin-offset on reducing noise and vibration due to piston slap is described. The vibration and noise signals are acquired experimentally on time response and then these are plotted on frequency response. The noise levels of the engine operating at maximum pressure at TDC (Top Dead Center), BDC (Bottom Dead Center) and at the middle of the stroke are captured. These correlation results show that maximum values of vibration and noise levels correspond to the TDC region where the stress levels are high. Hence, design optimization of the piston, cylinder-liner and other parts can be made to minimize the stress values so that the corresponding noise level is also minimized. One of the methods to minimize the piston slap noise is by providing the piston pin-offset. In the present study, the piston geometry is redesigned for the pin-offsets of 0.2, 0.3 and 0.4 mm. The noise and vibration frequency spectrum and plots of the noise levels (air borne) in terms of dB(A) are obtained by conducting experiments on a running Internal Combustion Engine. It is found from these observations that there is an improvement observed for both stress values and reduction in noise intensity, for the piston pin-offset of 0.3 mm, of the Internal Combustion Engine considered for the study.