Information from HKS Japan;
The key item of exhaust back pressure control with knowhow of HKS CZ200S(CZ4A). Maximization of performance from stock turbine is the concept of the product. Extension portion and front pipe portion are connected with a flexible joint. It improves “durability” that is an important factor of tuning. It offers new tuning possibility for EVO X.
• As stock turbine is small, it has good response at low rpm. At high rpm, due to exhaust resistance, feeling will be worse. By improved exhaust efficiency, boost pressure will increase earlier at low rpm and power & torque will be increased for whole rpm range up to high rpm.
• CAD designed complicated but ideal shape is manufactured with lost wax casting. Since lost wax casting items do not have welding portion, there is no problem of cracking by heat and the smooth surface guides exhaust gas flow smoothly.
• The turbine outlet is 2 ports independent shape for swing valve side and turbine impeller side to reduce resistance due to interference of gas.
• For street use, connection of extension and front pipe is flexible joint type like stock system to reduce vibration and to improve durability. Even lower side exhaust part is hit, it prevents damage to the engine or turbine.