Mechanical Testing and Diagnosis ISSN 2247 – 9635, 2014 (IV), Volume 4, pp. 17-24 MODELING OF PISTON SLAPPING MOTION Sunny NARAYAN* * Mechanical Engineering Department, University of Roma, ITALY email: rarekv@gmail.com ABSTRACT The aim of this work is to develop various analytical models for studying the piston slapping motion. The results of various methods are compared to the experimental results using block vibrations measurements on a diesel engine test rig. Both results correlate, validating the considered theoretical methods. Keywords: piston motion, slap 1. INTRODUCTION Piston slap is a major source of noise in automotive industry, which is a cause of concern for many car makers in order to devise methods for compilation with various emission norms, as well as to meet customer satisfaction. With many developments in this industry, the problem of NVH has become more significant, particularly in case of diesel engines. The decade of 60s saw the first attempt at governmental noise regulations that directed its efforts toward the automotive industry [1]. During the decade of 70s, new methods were developed by De Jong to study the piston slap motion, with focus on path for noise transmission [2]. Later, Ohta et al. presented an analytical model, taking into account block vibrations [3]. Later on, more work was done by Kamp and Spermann to evaluate and improve piston-related noise in engines [4]. Isuzu has also presented a mathematical model to study the piston secondary motion, taking into account hydrodynamic behavior of lubrication oil. 2. THEORETICAL BACKGROUND Piston secondary motion is due to striking of piston, with major thrust and anti-thrust sides of liner. Hence, it is necessary to develop an analytical model to study the piston dynamics motion along with the engine block vibrations, considering the piston transverse motion, the tilt angle and various contact forces. Many models have been discussed here to understand this motion. First, a point mass model of the piston slap has been discussed, which simulates the secondary motion, as shown in Fig. 1. The governing equations for this system can be expressed in terms of skirt-liner gap (e), mass Fig. 1. Point mass analogy model