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A calculation method has been developed to analyze and to optimize both the acoustic and performance aspects of air intake systems for internal combustion engines. The method integrates an acoustic linear one-dimensional computer code (SISASP) together with an acoustic linear three-dimensional computer code (SYSNOISE) and a one-dimensional thermodynamics analysis code (MARKPLUS XIV). The method enables the design of complete intake systems, integrating the acoustic and performance aspects and allows the designer to optimize the design to achieve legal, subjective comfort and engine performance targets. The results obtained from system simulations carried out in this way have been validated on a four cylinder gasoline engine and are illustrated here. The method can be used as part of the overall integrated design of an engine and also as a tool for intake system optimization.

In recent years, the development of sophisticated engineering resins for the automotive industry has expanded the applications into areas generally reserved for metals. Weight and cost reduction have been driving forces for most conversions, with noise reduction only a distant possibility. This study describes work in which a thermoplastic nylon 66 rocker cover was designed to reduce the overall noise emitting from a diesel passenger car engine. A 10% reduction of engine acoustic power output was achieved.