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Hydraulic engine mounts are used in the automotive industry because they offer frequency and amplitude response characteristics superior to the conventional elastomeric engine mount. This response is well established but is not fully understood. Numerous articles have attempted to explain the complex behavior of these mounts using linear theory. This paper uses the same linear models developed in previous papers, but offers a more fundamental explanation of the system response using these previously derived two degree of freedom models. In addition, the source of engine vibrations and their corresponding frequency ranges are explained in detail. Techniques borrowed from control systems are used to interpret system response and terminology used in the automotive industry to describe the behavior of hydraulic engine mounts is clarified. Validation of the two degree of freedom model is made by comparison with experimental data.

Recently an increase in interest has occurred in automotive powerplant mounting. Evidence of this growth is the increase in the number of publications on the topic. The majority of this renewed interest has come from predicting and understanding the response of hydraulic engine mounts and the application of optimization techniques to the problem of powertrain vibration isolation, and occasionally to the combination of these two topics. However, it appears that these analytical techniques have been sufficiently developed and correlated to actual powertrain systems to have found widespread use by the automotive manufacturers. Subject to timing and packaging constraints, the more traditional mounting system design strategies are typically utilized. These strategies include natural frequency placement, torque axis mounting and elastic axis mounting. This paper presents a comprehensive review of these three strategies including a discussion of the assumptions associated with each method.