Thread: Questions about GT2871R Turbine Housings and A/R..

Well

A GT28RS and 2871 share the same turbine wheel.

A GT28RS and 2871 are very fast spooling turbos.

The Turbine wheel and housing from a GT28RS will outflow its compressor wheel. On the 2871 the flow potential of both wheels are about the same.


Now the question is what AR housing do you want to run with a T3 Turbine housing vs the T25 .86 AR housing.

0.63 Andreas ,like I said before (on a agu motor) the 2871 52trim got almost the same spoolup 100-150rpm max diff and the transient responce was equal.. I cant said about power diff becouse of the comp wheel difference but I really can bet that if you put a 28rs for example same turbo manifold (except for the t3 flange) etc the 0.63 will out spool the 0.86 and make more power top end.

Well I dont see the T3 .63 out spooling the T25 .86 but I do see it making more topend.

A T3 housing of equal AR to to a T25 housing is way bigger.

bingo, it not like cams where you may loose 200-300rpm is spool up (boost threshold) but gain a lot of power in the mid range and top end and normally gain transitional response once on boost. It's the whole power delivery of the .86 that sucks


ok i defiantly agree with you from the 2871r onwards (gt30 etc), but i do think you get away with the t2 with the 2871r, only because its a small turbine wheel and its really the big comp that gives it its power.

I dont think you NEED a t3 with a T28 turbine, where as with the gt30 you pretty much do. I am not saying there arnt benefits to it, and if you want more power from the gt2871r i would rather a .63 t3 over a .86 t2.

but standard manifold, 2871r and .63 t2, 52 trim is a nice set up imo, but if you want more power than this can provide i would look into different options than the .86 and defiantly agree its t3 flange time

also miko a .63 t3 will flow around the same air as a .86 t2, but the reason why it outspools the .86 t2 is because it biggest restriction is just before the air hit the turbine wheel, which forces the air the speed up at that section. This is same reason the standard manifold has a splitter in it, to speed up the air before it enters the turbine housing. Where on a t2 .86 the t2 flange is probably the biggest restriction, so the air speeds up entering the turbine housing then slows down in the big .86 housing just before it hits the turbine wheel creating slower boost threshold and transient response.

Welll I just got a .64 a/r t2 gt2871r that was suppose to be a .86a/r so I am a little upset and this thread really upsets me more. I want 350 dd whp with this turbo and i want some nice topend too and am again scared that my 64 won't give me the topend and power I am looking for.......

How do you go about fitting a coupler/clamps and 3" inlet pipe on a 3" inlet turbo when mounted on a stock FWD manifold (GTi-R in my case)? I ask because I'm dealing with a similar situation on my car and have found I'm running into the block and transmission bell housing. It's tight enough to make me recommend against trying it. Do you have any advice?

By the way I agree with the rest of your recommendation, I just have questions about the 3" compressor inlet for my own personal gain.

Ben, I've been there before. With the GTiR or Avenier manifold you will need the 2.75" inlet housing. The 3" coupler will fit but you should put it on the turbo and clamp it down before bolting the turbo manifold to the block. Its a PITA though.

With the Bluebird manifold, the 3" inlet and coupler will fit.

you can always purchase a .86 turbine housing. I would not use the .64 housing on that turbo, but again I would also go external gate.

yep running the 2.75 inlet on my gt28rs(gti-r mani). its tight but fits with out grinding the block.

How does this thread upset you? If you got a .64 a/r when you thought it was .86a/r is either your mistake or the sellers, not this thread. I'm not understanding your post.

You should be able to reach 350whp and beyond w/your turbo. If not, get an S4 cam that should get you there.