An Analysis and Application of a Decoupled Engine Mount System for Idle Isolation

This paper addresses the issue of front wheel drive engine idle isolation. It establishes criteria for design and presents an analysis of an application. The approach was to model the powertrain and engine mounts as a 6 D. O. F., lumped parameter system, and decouple the five highest frequency rigid body modes from the direction of the idle torque pulses (crankshaft rotation direction).

A packageable decoupled mounting system was obtained by using a Ford in-house program for simulating dynamic systems (MOTRAN) and a structural design optimization program (OPUS).

A baseline mount system and a decoupled mount system were installed and tested in a production vehicle. A three cylinder engine with similar inertia properties to the production four cylinder engine was used for the analysis and vehicle evaluation. A simulated idle test and an actual engine excited idle test were performed on the vehicle. A factor of two reduction in vehicle interior vibration levels was obtained with the decoupled mounting system at the frequency band of interest.