A stock extension is designed to merge the main port (turbine exhaust) and bypass port (wastegate actuator) in turbine exhaust housing. This causes the exhaust stream from the main port to interfere with the bypass port stream when the actuator is opened. The primary and secondary exhaust pressure will rise causing the boost pressure to drop, which can cause a loss in power. The HKS Extension Kit will optimize the turbines performance with minimal power loss.

The HKS Extension Kit utilizes an individual main port (turbine exhaust) and bypass port (wastegate actuator) to reduce the exhaust gas interference and provide a smoother exhaust flow. This will also reduce backpressure and improve the boost response throughout the RPM range. Even with the stock turbine, the exhaust gas merges in the exhaust housing. This exhaust gas interference can be prevented by a divider in the exhaust flange. The pipes connect towards the lower part of the extension housing where the exhaust gas pressure is lower. The main pipe's diameter is enlarged at the turbine outlet so the swirl flow caused by exhaust gas interference can be reduced. This will also prevent the secondary exhaust pressure from rising, and stabilize the boost pressure to increase the engine output. The flange is made with a high structural steel material, and the piping is made with a high heat resistant and durable Stainless (SUS304). These components will also improve the engine compartment appearance.