Effect of Engine Mounting Strategy on Vehicle NVH

The primary task of a powertrain mounting system is to keep the powertrain located properly in the vehicle, provide good motion control as well as good isolation. Although there are a variety of other requirements and constraints, this study focuses on the NVH aspects. While most mounting systems have the same primary function, there is a large variety of mounting systems in use in the automotive industry. This paper examines a couple of the design strategies, involving powertrain rigid body mode coupling and de-coupling. These strategies call for the rigid body modes of the powertrain, whose mounts are fixed to the ground, to have certain coupled or decoupled characteristics. Since the powertrain related NVH is affected by its behavior in the vehicle, which is often quite different from that on the ground, this study investigates the usefulness of such strategies. This study compares three such strategies that are commonly used. All decoupled modes, coupled bounce-pitch modes, and coupled bounce-roll modes strategies are compared by looking at the response of a vehicle model, to wheel and powertrain inputs. Then the three systems are optimized to minimize the vehicle response to those inputs. The on-ground rigid body modes of the powertrain from the optimized system are compared to their original starting points. This study highlights the use of such modeling based techniques, to optimize the powertrain mounting system, that can be used in very early stages of a program, before any resources are expended on building prototypes.