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. The challenge of this process is partially due to the lack of precedence for cylinder deactivation with or without a valve, as well as, condensed timing of the program. The results were no perceivable subjective change from tailpipe acoustics.
A classical thought process for managing this challenge has been the use of an actively controlled valve in the exhaust system. This method temporarily reduces the system's volume, increases its back pressure, and overall reduces airborne noise. The active system is not without risk. There are issues that could arise from valve malfunctions and the substantial variable cost to the exhaust system. This paper presents a passive exhaust system that does not require a valve which is driven by CAE design.