PISTON ENGINE INTAKE AND EXHAUST SYSTEM DESIGN

The aim of intake and exhaust system design is to control the transfer of acoustic energy from the sources and its emission by the system with minimal loss of engine performance. A rational design process depends on the adoption of a design methodology based on predictive modelling of acoustic behaviour. Virtually any system geometry can be modelled by breaking it down to a sequence of simple elements or chambers. An initial design layout is then produced with simple parametric models of individual element behaviour. This design is then refined to prototype level by systematic modification of detail using realistic assessments of system performance in its operational environment. Following prototype validation by practical testing any further necessary development is again assisted by predictive modelling. The application of appropriate procedures is illustrated by a series of practical examples. These concern improvements in interior noise by control of intake noise, of vehicle performance by reducing flow losses, of the environment by control of exhaust emissions and lastly with the control of flow noise. This account concludes with a brief outline of current and new developments involving integrated hybrid design procedures. A further paper is being prepared describing silencer designs with their experimental validation.