Piston slap noise reduction in IC engines: design improvements by advanced signal processing techniques

The reduction of piston slap noise is pivotal for a good design of IC engines. In this scenario, a methodology has been developed for the vibro-acoustic improvement of IC diesel engines by means of design changes of piston to cylinder bore clearance. Vibration signals have been analysed by means of advanced signal pro- cessing techniques taking advantage of theory of cyclostationarity in real IC diesel engines actually equipped on cars. The procedure departs from the analysis of the Continuous Wavelet Transform in order to identify a representative frequency band of piston slap phenomenon. Such a frequency band has been used as the input data in the further signal processing analysis that involves envelope analysis. An experimental procedure of vibrational benchmarking is proposed and verified on different operational conditions. The results underline the crucial role of the transducer positioning when slight changes of the system are considered.