Aftermarket exhaust parts restrictions in the system—can similarly increase performance, though would likely be illegal in areas where tampering with emissions devices is prohibited, particularly when placed in front of the catalytic converters. Aftermarket exhaust parts Aftermarket exhaust parts are intended to replace the factory fitted exhaust components of a car, motorcycle, or other motor vehicle in order to improve the performance, visual appeal, or sound of the vehicle. Generally, performance enhancements are achieved by reducing the back pressure of the factory exhaust system. Frequently a side effect of a free-flowing exhaust system is either a "different" sound, a higher noise level, or
Steam locomotive exhaust system reason the blower is often turned on in these situations, to counteract the compression effect. The aim of exhaust system development is to obtain maximum smokebox vacuum with minimum back pressure on the pistons. Little development of the basic principles of smokebox design took place until 1908, when the first comprehensive examination of steam-raising performance was carried out by W.F.M. Goss of Purdue University. These principles were adopted on the Great Western Railway by Churchward. Andre Chapelon made a significant improvement with his Kylchap exhaust which incorporated a "Kyala spreader" (second stage nozzle) and third stage cowl between the blastpipe