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This paper analyzes the relation between sound pressure at tailpipe and exhaust Y-pipe structure. The length of Y-pipe influences sound order distribution that influences customers' responsiveness of sound. The equal Y-pipe remains the firing order and its harmonic contents while suppressing the half order and other whole order sounds. Various lengths of equal Y-pipe also influence the magnitude and frequency distribution of tailpipe noise. An air-to-air (induction-engine-exhaust) CAE model is built to predict tailpipe noise using up-to-date software. The real air-to-air model simulation shows that the 3rd and 6th orders are the dominating contents for equal Y-pipe exhaust system in 6-cylinder engine applications. The sound pressure of the half order contents increases with the length difference between two branches of a Y-pipe. The results are useful for exhaust Y-pipe design.

This paper summarizes the attributes of automotive exhaust system and provides a guideline for exhaust system design, analysis and development. The exhaust system has various attributes including vibration, acoustics or noise, durability and thermal distribution, flow and power loss, emission, in addition to its interface with vehicle. This paper describes all these attributes and the corresponding performances, and develops criteria for each of the attributes. The paper also describes the interfaces between the exhaust system and powerplant with body structure.