Krueger, J., Pommerer, M., and Conrath, M., "Efficient Exhaust Silencers for Downsized Gasoline Engines," SAE Technical Paper 2012-01-1563, 2012, doi:10.4271/2012-01-1563.
In recent years, the ANC technology was adapted for intake and exhaust systems on several passenger vehicles with a variety of diesel and gasoline engines. In these predevelopment activities, the active components (actuators, electronic hardware and software) were rigorously improved and its durability professionally validated leading to an increased system performance even under very harsh conditions. Depending on the customer targets, this yielded several benefits when compared to conventional exhausts. For example, a passive conventional dual exhaust system of a highly efficient 4-cylinder gasoline engine could be replaced by an active single exhaust line without compromising on the acoustic targets but saving a considerably amount of design space and weight. In particular, the space advantage can be utilized to create innovative exhaust layouts.To support future downsizing of engines, for example, an ultra-compact exhaust layout is proposed. By concentrating all parts of the exhaust close to the engine, e.g., within the engine bay, further space in the underbody of a vehicle is released and can be used for installing other equipment (e.g., batteries in hybrid electric vehicles) or optimizing underbody flow conditions. Consequently, the active exhaust technology leads to an overall optimization of the vehicle design and could eventually support an even lower CO₂ emission of future vehicles with downsized and hybrid engines.