Complete NVH optimisation of a passenger vehicle with a D. I. diesel engine to meet subjective market demands and future legislative requirements

For optimisation of total vehicle noise-vibration-harshness (NVH) the interaction of the power unit and other noise sources with the power unit mounting system, the vehicle chassis structural response and the vehicle local transmission losses have to be taken into account. In this paper the procedure adopted for optimising the NVH of a production off-road vehicle equipped with a DI-TCI diesel engine is reported. The short time scale available for the engine and vehicle project demanded the adoption of a refined strategy which allowed, in parallel, both a low overall noise level and a high quality noise character to be achieved by feasible and cost effective methods. This combined approach adapted for balancing and controlling engine noise, other vehicle noise sources and vehicle response with respect to exterior and interior noise and subjective noise character, is discussed.