Vehicle NVH Prediction Technique for Engine Downsizing

As fuel prices continue to be unstable the drive towards more fuel efficient powertrains is increasing. For engine original equipment manufacturers (OEMs) this means engine downsizing coupled with alternative forms of power to create hybrid systems. Understanding the effect of engine downsizing on vehicle interior NVH is critical in the development of such systems.

The objective of this work was to develop a vehicle model that could be used with analytical engine mount force data to predict the vehicle interior noise and vibration response. The approach used was based on the assumption that the largest contributor to interior noise and vibration below 200 Hz is dominated by engine mount forces. An experimental transfer path analysis on a Dodge Ram 2500 equipped with a Cummins ISB 6.7L engine was used to create the vehicle model. The vehicle model consisted of the engine mount forces and vehicle paths that define the interior noise and vibration. The same engine mount forces were calculated analytically and imported into the vehicle model to compare against experimental results. Good correlation between engine mount forces enabled the vehicle model to be used with analytically calculated I4 engine mount forces to predict interior response.

The predicted interior noise and vibration results were used to define powertrain bending and engine radiated noise and vibration targets.