HKS is a company that is known for long time exhaust developments targets to pull out 100% engine performance with the Stainless steel exhaust manifold. A lot of different approaches were tried for each vehicle to keep performance for middle rpm range and to improve horsepower at high rpm.
Reduced pressure with Bypass Pipe (Racing Header)
When strong vacuum is created, to the contrary, there also is strong pressure. Cylinder pipes are connected with Bypass Pipe to reduce pressure as minimum as possible. Rhythm of "Pressure" and "Vacuum" inside manifold is controlled. Besides, number of bypass pipe and positions are designed to optimize for each engine characteristics. It enables to reduce pressure without change of vacuum. Therefore, there is no drop of torque. The engine will have Inertia Exhaust Gas Efficiency (Efficiency to increase horsepower of NA engine) and flat torque characteristics, which enables easy drivability.
Advantage of 4-2-1 Straight Junction (Super Header)
HKS selected 4-2-1 junction design that has best result for street use from study of various data about a lot of engine characteristics and exhaust gas pulse. 4-1 Junction type has shorter length to the junction part and it is better for competition purpose that require performance only at high rpm range. But it has too less torque at low rpm range for street driving. HKS'' Straight Junction Design accelerates exhaust gas with exhaust gas pressure and it pulls out combustion gas. Exhaust gas efficiency is improved with the design.
