Perforated Muffler Manifold Catalyst

An alternative exhaust manifold system, the Perforated Manifold, Muffler, and Catalyst (PMMC), is proposed to improve sound suppression while reducing engine pumping losses and exhaust emissions. One-dimensional predictions from acoustic theory are used to configure the initial design. Preliminary evaluation of the concept is based on bench tests, including an extended impedance tube set-up for acoustic attenuation and a flow bench for flow loss characteristics. Experiments with the fabricated hardware are then conducted in an engine dynamometer facility, and the results were compared to the existing production system as a benchmark. Engine experiments show that the PMMC concept provides enhanced upstream sound suppression, reducing the need for restrictive downstream silencers. This results in reduced engine pumping work and thus improved engine brake horsepower. Additionally, conservation of exhaust gas thermal energy and the reduced thermal inertia of the exhaust system provides earlier catalyst light-off, and therefore reduced pollutant emissions. 7 1998 Academic Press