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
Four-stroke power valve system to develop such a system, called the Exhaust Ultimate Power Valve (EXUP). It first appeared on the Yamaha FZR EXUP and was later used on many other Yamahas. Later versions from Honda went by the names Honda Titanium Exhaust Valve (HTEV) and Honda Variable Intake/Exhaust (H-VIX), appearing on the CBR600RR and Honda CBR929RR. Suzuki's version is called Suzuki Exhaust Tuning (SET). The system is also used on the Triumph Daytona 675 triple. Four-stroke power valve system A four-stroke power valve is a device fitted to four-stroke engines that constantly adjusts the internal diameter of the exhaust system to better suit