Valvetrain Unbalance and Its Effects on Powertrain NVH

As vehicle NVH continues to improve, automotive engineers have continually worked at identifying and ameliorating smaller and smaller sources of engine vibration. In this search, what has become an extremely important factor is often overlooked, namely valvetrain related engine unbalance effects.

This paper will present a simple analytical approach to the calculation of valvetrain unbalance effects. Theses unbalances will be compared in magnitude to the well understood inherent cranktrain unbalances. The paper goes on to explain the significant factors that control the directions and magnitudes of these forces and moments. Experimental validation of the analytical procedures will also be presented.