Wastegate Flapper Upgrades

Standard IHI flapper beside Black Hole Flapper

In some cases, when turbocharged cars are fitted with free-flowing exhausts, the owner will start to notice boost creep.  This is caused by a mechanical limitation in the turbocharger's turbine housing assembly.  Once backpressure is reduced, even with the wastegate fully open, it cannot vent enough exhaust to prevent boost pressure from rising above the target.  Sometimes porting can improve this, but in many cases a larger wastegate flapper must be made and installed, and the wastegate thru-hole modified extensively.

As an example: With the larger 2.5L engines used in the STi and other models of Subaru, sometimes the smaller IHI turbine housings cannot handle the increased levels of airflow.  The wastegate on these turbos is very small, and even when fully open, it can still allow boost levels to rise beyond target boost with a free-flowing exhaust system.

In some instances (about 10% thus-far) the addition of a larger Wastegate flapper can create a situation where the wastegate actuator begins to open early.  This can easily be solved by switching out the "pill" or restrictor in the actuator vacuum line.

Features :

Decreased boost creep with high flow exhausts

More solid boost control

Details :

Small flapper removed from turbo turbo

Opening greatly enlarged

Larger flapper installed

Pricing :

Wastegate flapper upgrade only - $69.99 + return shipping the turbo back to you. (Shipping specials WILL NOT apply)

We can/will offer some discounts on the wastegate flapper upgrade if you have your turbine housing ported at the same time.