NVH Refinement of Diesel Powered Sedans with Special Emphasis on Diesel Clatter Noise and Powertrain Harshness

NVH refinement of passenger vehicles is crucial to customer acceptance of contemporary vehicles. This paper describes the vehicle NVH development process, with specific examples from a Diesel sedan application that was derived from gasoline engine-based vehicle architecture. Using an early prototype Diesel vehicle as a starting point, this paper examines the application of a Vehicle Interior Noise Simulation (VINS) technique in the development process. Accordingly, structureborne and airborne noise shares are analyzed in the time-domain under both steady-state and transient test conditions. The results are used to drive countermeasure development to address structureborne and airborne noise refinement. Examples are provided to highlight the refinement process for “Diesel knocking” under idle as well as transient test conditions.

Specifically, the application of VINS to understanding the influence of high frequency dynamic stiffness of hydro-mounts on Diesel clatter noise is examined. In addition, examples are provided from studies aimed at reducing the perceived powertrain harshness under on-road operating conditions. Finally, the results from these studies are summarized and appropriate conclusions drawn with respect to the Diesel sedan NVH development process.