GTM Performance Engineering: MHI Twin Turbo Official Release

Originally Posted by SAM@GTM

The reason the aftermarket STi cats don't fail is quite simple. They are designed for the application. Mounting the cats farther away is actually a bad thing and shortens the life of the cat since it needs heat to do its job. The better Subaru Downpipes use correct cats and mount them in the factory location right after the turbo outlet. The HFC's currently on the market for this car are NOT designed to handle Forced Induction.

We will be offering high flow cats as part of our new modular downpipe design. These cats are designed specifically for high horsepower, forced induction applications. In fact, we are so confident in their performance that we will be offering a warranty against failure.

The HFC's we will be offering are for our 3" downpipes with external wastegates as an option. You can also swap to 3" test pipes for track days if you like since they are bolted pieces. This new option is a great way for people to go that want 500whp and still have clean exhaust. Also, these cats will keep emissions down just as well as the stock cats, but have more flow and stand up to higher exhaust temps with richer air/fuel mixtures.

Sam