Merge collectors has been part of professional race setups long ago and only now begin to be incorporated into street header applications. In order to maximize torque and horsepower, it is imperative that a vehicle's header and exhaust system are able to optimize exhaust gas velocity. Anything which reduces exhaust gas speed will leave a bad impact on ones performance. A racing header featuring a conventional collector generally suffers from a significant reduction in exhaust gas velocity at the transition from the primaries into the collector and this drop in velocity will decrease volumetric efficiency and reduce scavenging ability. That is the key since optimizing volumetric efficiency of an exhaust system allows for improved air/fuel mixture in the combustion chamber, there by improving an engine's horsepower and torque production potential.
A Merge Collector that is fabricated properly will significantly minimizes the exhaust gas velocity loss at the transition from primary tubes to the collector and as a result, the volumetric efficiency potential of an exhaust system is significantly improved.