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A new passive muffler valve has been developed that offers the advantages of both the current passive and active valves without their major drawbacks. Like current passive valves this new valve provides high restriction at low to medium engine speeds for improved noise control. But with a near over-center spring action and unique flap shape, this high performance valve has minimal pressure drop at high engine speeds, closer to the active valve pressure drop performance. The in-line design of the valve makes it ideal for low restriction OE mufflers, resonators, and aftermarket performance mufflers. The new valve design is uncomplicated, with few components and has been tested extensively for durability utilizing both bench and vehicle level testing.

To facilitate the design and validation of exhaust system, quantification of tailpipe noise contribution to vehicle cabin is usually necessary. In this paper, transfer path analysis (TPA) concept has been applied to investigate the contributions from tailpipe and other noise sources as well as the interaction between tailpipe noise and its transmission path to vehicle cabin. An artificial acoustic source has been designed for transfer function measurement and an all-wheel-drive dynamometer located in anechoic chamber is used as a testing platform to collect operational data. A validation methodology has also been proposed and implemented by comparing the measured and predicted interior noise response with a big auxiliary muffler (BAM).