Future Legislation on Noise and Emission of Vehicles and the Impact on the Design of Exhaust Systems

Over the past few years, the measurement procedure for the pass-by noise emission of vehicles was changed and new limit values have been set by the European Parliament which will come into force within the next few years. Moreover, also the limits for chemical emissions such as NOx, particulates and CO₂ have been lowered dramatically and will continue to be lowered according to a roadmap decided not only in Europe but also in other markets throughout the world. This will have an enormous impact on the design of future passenger cars and in particular on their powertrains. Downsizing, downspeeding, forced induction, and hybridization are among the most common general technology trends to keep up with these challenges. However, most of these fuel saving and cleaner technologies also have negative acoustic side effects. As many customers are not willing to compromise on sound quality, innovative technologies have to be developed to keep or enhance the NVH performance of future vehicles, powertrains and last but not least exhaust systems. This publication will give an overview of different active approaches to exhaust technologies. The benefits of these technologies are compared to conventional cold end systems in terms of parameters such as acoustic quality, volume, weight, and backpressure.