Reduction in Exhaust Noise Through Exhaust Valving Modifications Achieved with a Gas Dynamics Simulation Model

One of advanced requirements in current high output power engine design, as is seen in a four valve engine, is to reduce the exhaust noise without a reduction in engine performance.

In order to examine the relationship between output and exhaust noise level, a gas dynamics simulation model was extended so as to predict the exhaust generated noise. The gas dynamics model used in this study is developed based on a finite difference method in which unsteady compressible flow is solved by two-step Lax-Wendroff method.

Using this simulation model, timing changes were found to be effective in reducing the exhaust noise level without showing any trade-off on engine performance.

These results were validated by the experiment.