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The exhaust system is one of the major P/T systems for sound quality tuning. The many varieties in exhaust pipe routing and the flexibility in muffler design make it possible to design an exhaust system to deliver tailpipe sound for specific sound quality requirements. It is essential that the tailpipe sound be balanced with other P/T sound to yield the overall sound targets. The primary contribution of an exhaust system is the firing and sub-firing orders. The typical tailpipe sound target contains banded targets for “good” orders as well as “do-not-exceed” targets for the rest. Every order target needs to be met in order to yield the right tailpipe sound. In most cases, the pipe routing and the muffler volumes of mufflers are dictated by package constraints, however, the internal design of muffler with a given volume can create quite different tailpipe sounds.

Cylinder deactivation is an efficient way to significantly improve fuel economy without compromising the horsepower and torque. For an exhaust system to manage both V4 and V8 modes, a unique development approach for exhaust system design needs to be incorporated. Simulation tools and correlation testing can be used to achieve great sound quality without the use of an active valve design classically (believed to be required) implemented. A quasi-Computer Aided Engineering (CAE) 1-Dimensional code drove the design of the passive (without a valve) system. The 1-Dimensional code analyzes pressure waves, mass flow and energy losses in ducts and junctions. To achieve the objective for cylinder deactivation, this tool also allows significant changes with relatively fast results for trends to be evaluated. The goal for this cylinder deactivation system was to have a smooth transition between the two modes and achieve the commercial performance with low backpressure.