2871R; bottom mount tubular or T3 log?

[Seraphim38]

Which would be better performance for a daily driven/HPDE/occaisional autox car: T25 tubular bottom mount with .72 external 44mm vband wastegate ATP housing, or T3 top mount with 38mm external wastegate?

T3 will flow more but I don't know about using a log manifold (though it won't be prone to cracking like the tubular one will do some day).

At this point there isn't a lot of difference in cost, except that with the top mount option I will have to buy a new turbo elbow, down pipe and intake.

[fliprayzin240sx]

Sounds like you're more worried about cracking manifold since you're opting for a log style T3 manifold. If thats the case, hit up Codyace and opt for a stock bottom mount manifold and he can extrude hone it to flow like alot better and weld a 44mm vband flange on it. Opt for a run of the mill GT2871R .63 if you want response or .86 if you want more top end/maybe extra 50hp but slightly laggier.

http://www.codyace.com/albums/album20/manifolds_01.sized.jpg
http://zilvia.net/f/forced-induction/429481-external-wastegate-stock-manifold-true-boost-control-your-sr20.html

[Seraphim38]

yup, I have seen that thread/manifold. I just figured that taking it to a T3 flange while I am at it would make more power, but probably that's more relevant with a .86 than the .64 that I currently have.

[codyace]

T3 and response really don't go hand in hand at all. If you're looking for a turbo to match your intended goals of 'daily driven/HPDE/occaisional autox', I'd strongly suggest the T2 flanged turbos, namely the .64 housing ones.

Response, torque, boost onset...all are best with the smaller housing (however at the expense of a little top end power). In the grand scheme of things, this side of constant street racing, unless you're making more than 450whp on T3 based setup, a 380-400whp T2 based car will be quicker in all accounts, aside from top speed.

[fliprayzin240sx]

SInce your in here Cody, could you hypothetically make a T3 flanged .86 spool up like a T2 flanged .64 (less lag)?

[codyace]

SInce your in here Cody, could you hypothetically make a T3 flanged .86 spool up like a T2 flanged .64 (less lag)?

I don't think you could ever get it close...the T3 flanged stuff is just simply more area to fill, and you're not getting the backpressure advantage of spool up either like the T2 has.

FWIW (and I know you know this) Truthfully if you're going with a T3 flange, I'd run a larger 3Xr and make some real HP. I don't get the point of the 3071/3076r especially when the 35r isn't that much laggier, yet has higher power potential. In my world, the only other option beyond 2871r is 35r.

[Seraphim38]

Hello Cody,

Given the goals for the car and input from my mechanic and tuner, along with people such as yourself, I have elected to keep my GT2871R but I am going to upgrade to the T25-EWG-44 exhaust housing, with the ATP 90 degree elbow, Precision Turbo PT46 v-band wastegate and ATP dump pipe. Manifold will be a new old stock Greddy bottom mount tubular. The car will be going to PSI in Portland in about 2 weeks to get an AEM EMS Series 2 installed and thoroughly tuned. If you stocked an external wastegate modified manifold, and even had one with extra goodies like swain or extrude honing treatment, I would consider it.

Thank you for your ongoing support of the community, and willingness to share the breadth of your knowledge.