Abstract
Eigenvalue analysis is one of the commonly used methods to reproduce quite complex vibration shapes of an engine under operating conditions. However, the reproducibility is often poor due to its insufficient modeling. In order to solve this problem, a new method using modal analysis has been developed. This new method was applied to a front-engine front-drive power plant of an in-line four-cylinder gasoline engine, and it was confirmed that the accuracy of prediction was sufficient for practical use with the same simplicity as eigenvalue analysis. It was also found in this case that "the box-shaped rear skirt" was the best structural modification in terms of weight effectiveness for the reduction of the power plant vibration.