turbo selection?

[s.tamayo1991]

Hello. So i have an s14 sr at the moment with a stock t28. I autocross the car and occasionally i drift. Im upgrading my turbo soon and i want something that would be best for both. My question is on a stock sr (built bottom end) what has more TQ at 3500 rpms: S15 turbo, GT2871r or Tomei M7960.

With whatever turbo i get i will be using the stock manifold with an external wastegate.

Also, will Tomei Poncams bring down the torque at 3500 rpms? or for my purposes should i keep the stock cams?

Car will also be tuned by RT Tuning.

[Croustibat]

S15 turbo is the same as s14 turbo. Only the first series of japanese s15 specR had a ball bearing cartridge. If you want "the s14 turbo with roller bearings", it is called the gt2560r from garett.

Go with a gtx2867r and a new manifold. Forget cams, you don't need them. If you don't already have one, get a FMIC.

Depending on your power goal and fuel, you may need bigger injectors too.

[s.tamayo1991]

Originally Posted by Croustibat

S15 turbo is the same as s14 turbo. Only the first series of japanese s15 specR had a ball bearing cartridge. If you want "the s14 turbo with roller bearings", it is called the gt2560r from garett.

Go with a gtx2867r and a new manifold. Forget cams, you don't need them. If you don't already have one, get a FMIC.

Depending on your power goal and fuel, you may need bigger injectors too.

i currently have tomei 740cc injectors, FMIC and tuned on an APEXI Power FC. I dont have huge hp goals. Ill be good with 300-320. I just want the most power in the lower rpms as possible.

[angel mkiv]

I agree with a above get a gtx2867r in a .64 turbine housing! As for cams I'm not sure for a s14 sr but on my s13 I have jwt s3hl cams and my car crazy response and low end power

[RalliartRsX]

Originally Posted by Croustibat

S15 turbo is the same as s14 turbo. Only the first series of japanese s15 specR had a ball bearing cartridge. If you want "the s14 turbo with roller bearings", it is called the gt2560r from garett.

Incorrect

S14/S15 auto
Compressor: T-28, 60 trim 60 mm BCI-1 compressor in T-04B housing

Turbine: T-25, 62 trim 53.8mm 0.64 A/R turbine housing.

Center Section: Ball Bearing

S15 manual
Compressor: T-28, 60 trim 60 mm BCI-1 compressor in T-04B housing

Turbine: T-25, 60 trim 60mm 0.64 A/R turbine housing.

Turbine: Inco turbine wheel. Cast divider wall between turbine discharge and wastegate.

Center Section: Ball Bearing

The turbine wheel is also larger on the s15 turbo.
Max efficient psi on the s14 turbo is about 14 psi. Max psi on the s15 turbo is around 18 psi. Max hp on the s14 turbo is around 280 and on the s15 it's 300+

OP, torque at whatever HP is based almost entirely on tuning (and supporting parts. A JWT C series cam vehicle will not produce the same torque figures as a similar vehicle with JWT S3 series cams at given RPM). You need to look at the compressor maps to give you a better idea.

Also, just based off a hunch, it seems the M7960 and the GT2871R have pretty simiilar specs

I do however recommend the GTX series of turbos as they do have a better designed compressor wheel and is able to flow more (more HP) for a given PR over a comparable GT28, etc.

[Croustibat]

Anyway, my point is they perform similarly, and "an S15 turbo" is not guaranteed to come with a BB core.
For 300/320hp i would not even bother changing the turbo unless it is on its way out. And then... it seems gt2560r have become cheap, so it could be a solution. No need for an external wastegate either.

A gtx2867r is good enough for 400+, same goes for a 2871 which is older tech. You could eventually go gtx2863r but i don't think it is a turbo suited for a 2L+ engine.


Here are 2 dyno sessions from engines my tuner made. Both are with sr20det. Both cars competed in the french drift cup.

The first one is nearly an "all out" build with a lot of expensive parts, a gtx2867r with twinscroll and dual external wastegate and a fullrace manifold. The exhaust had a nasty jasma restrictor, the engine got a good 20HP more when it was removed.

https://vimeo.com/65543081

The second is way cheaper, with an internally gated gtx2863r and a docrace manifold.
https://vimeo.com/72344366

[Kingtal0n]

I agree with crousti, a brand new BB turbo from garret will run you $1100~ whether you buy a 320HP or 480HP turbo.

Usually we enthusiasts are looking for the best dollar/hp ratio and a turbo upgrade is the epitome of that in a sense. Here your $1000 can get you 40hp or 120hp...

[Kingtal0n]

Originally Posted by s.tamayo1991

Also, will Tomei Poncams bring down the torque at 3500 rpms? or for my purposes should i keep the stock cams?

You need a camshaft upgrade to take advantage of the head at higher rpm. Torque will be reduced slightly through 3000-4500rpm on nearly every aftermarket camshaft, which is a good thing, it will make your peak torque less likely to cause engine knock at high boost with low (93) octane, it will also lessen the sudden "hit" from spooling the turbo that breaks tires loose when you are trying to go straight so you can keep your foot down. The power will come in more progressive instead of suddenly and the car will be more easy to control and "aim".

people looking for 350rwhp on a stock sr20det engine usually go internally gated 2871r (or similar BB garret turbo) for simplicity, with some S3 JWT cams to keep the OEM springs and 6800rpm redline for longevity.
use 9* btdc of ignition timing at 18psi through mid-range to start with and have an EGT gauge tell you whats what.