FREQUENTLY ASKED QUESTIONS (FAQ)
FAQ #2: Garrett T04B frame compressor housing air leak (between compressor housing and backplate) causes a significant negative impact to perfromance? ANSWER: NO, Garrett designed the GT and GTX series turbochargers with a "T04B" frame size compressor housing (.60 A/R, 3 inch inlet and 2 inch outlet hose connections) without a o-ring at the contact point between the compressor housing and backplate. The contact point was intended for a metal to metal interface with minimal amount of air leakage designed into the system. As a result, the contact point has a minor leak during a boost pressure test of the charge pipe system. The leak is 100% normal and factored into the performance of the turbo. The leak causes a neglible loss in pressure and will not cause a measurable impact to the turbo's perfromance.
The Garrett "T04B" frame size compressor housing is commonly found on Garrett GT28 and GTX28 series turbocharger models. Additionally the "T04B" frame is available as a compact housing option for the Garrett GTX29, GT30, GTX30, GT35, and GTX35 series models. Numerous turbo kits require the "compact" compressor housing to fit a Garrett performance turbo into a limited space engine bay.