Thread: Difference Between .86 & .64 A/R GTI-R t28

I have a GTI-R T28 according to the compressor and CHRA i just did a fresh rebuild and am starting the turbo prep on the car and noticed the Turbine housing is a .64A/R. My question is how much this will effect my setup

JDM DE ; 3" exhaust ; Calum Realtime ; S4 ; z32 blowthrough ; STI injectors ; F38 wastegate ; fmic

I plan to run this at 12psi and use it for autocross (not drag) so big hp numbers aren't important but i dont want to be choked up on the top end.

What are your opinions. should i try to get the correct .86 A/R turbine housing or just rock the .64

any help would be greatly appreciated.

.86. I wouldn't bother with anything else imho.

rock what you have no need for the extra money for what you are using the car for.

For autocross, the .64 A/R is perfect with a small frame T2 flanged turbocharger. Quick spool, and it generally won't fall flat on it's face well before redline.

I would not run anything smaller than a .86 turbine housing on a t2 turbo. You will lose some top end and gain some response with the smaller housing.

This isn't a roadcourse that he's mentioning. AutoX are generally much shorter and require more response than top end, or am I incorrect in thinking this?

The .86 can spool just the same via improved volumetric efficiency.

Just look at a dyno graph of most T3 turbos. .63 vs .82. The .82 spools the same and makes a crap ton more power peak.

to each his own though. for sure the .64 should be potent enough.

this depends on where the autox is held and how big the run is. It really comes down to traction like any thing else you do with a FI fwd car. You are correct response is important.

why would it make sense for him to spend more money when he has a perfectly good setup?

how do you know it will work. I doubt you have turbine maps for a turbo that did not come with a .64 housing. I would want the correct housing for my turbo. This is not to say it will not work well. It may work really well with a external gate.