Haha this is like the third time I've said .62a/r, yeah? Oh well, I'm over it. I was very tired when I wrote that message, hence the incomplete, half-*** post.

 

T25 = .64 and .86
T3 = .48, .63 and .82

Yes, they do go bigger but way to big for a 1.8t. All t25 housing should be a .64 since it is best suited for the 1.8t. YOu can use a .86 on a gt28rs and gt2871rbut they will be laggy. The .48 T3 housing should only be installed on a 50trim, gt28rs and gt2871r. The .63 housing should be use for all gt30 turbos (unless you already have a t25 turbo and manifold) and the smallest turbo you should use a .82 housing on is a gt3076r. Expect about 500rpms of lag for the larger housing, however you will get a greater top end and smoother powerband.

Also remember that the T3 flange is larger than the T25 so it flows more, also the t3 housings flow better also.

 

Cincy, if you have a .86 on a gt28rs, does the power carry through redline? I'm wanting something that's smoother and provides a nicer distribution of power. I absolutely LOVE turbo lag, too.

I know that a/r doesn't affect compressor performance, but it'll decrease backpressure at higher RPMs, given the larger housing size, so more power can be carried through.

 

It will have a smoother powerband like you need. The power will still drop off before redline, but not as much. However since you have a girly tip, you might not want a laggy turbo since you cant control when the car shifts.

 

I never ever drive without putting it in tiptronic mode. Ever. I shift when I want!

Okay, now that we've been past that, would you still recommend a smaller a/r so I can utilize my torque range efficiently? I don't want something that'll surge and put a lot of stress on the TCC all at once.

 

A gt28rs wont surge with either housing. A .64 will hit full boost ~3.2k and the .86 closer to 3.7k (increase housing is usually 500rpms). You will make boost before that, just not peak 20+ until then.

 

Does the RPM rule generally apply to the range of power that's carried through redline? IE you have more power before succumbing to backpressure by 500rpm in the high-end too? If not, I wouldn't mind waiting another 500rpm to experience a broader range of power in the long-run.

Y'know, you should consider hopping on AIM if you can [8D]

 

With a larger housing you are pushing back peak tq and will have more hp up top. You should see about 10-15whp gain on the same psi.

 

I noticed you ignored the second part of my response.

Anyways, I'm going to figure some stuff out between the t3t4 turbo that I wanted (57trim .63a/r) and this GT28RS. I'm not even sure which I want to start building my car for, but I guess my decision can wait. It'll be at least 2-3 months. Is it safe to assume the builds are going to be somewhat similar? IE the MAF, turbo inlet, injectors (based on software... is there 630cc software for the gt28rs?)

 

Yes, it will work with both. I am doing other things and dont have the time to hop on there