RB25DET turbo sizing. . . . ?

[Wykid 240]

Hello,I'll be putting an RB25DET in my '91 240SX in the next month and I'm wanting to know what turbo will get me the goal I'm lookin for. It'll be manly a street driven car and will see drifting and little drag so I'm lookin for a turbo that'll spool up quick, like start at 2500rpm's and full boost by 3500rpm's. My WHP (wheel horsepower) goal is 400-450whp. . . . I was thinking of a T3/T4, but I don't know what size and trim to get. I know that you all have had the RB25DET for long time and know what works. What I have now is the Greddy intake manifold, Q45 throtle body and MAF meter, Power FC, 500cc injectors and Apexi GT-spec ("4 inch) exhuast and a Hybrid FMIC. So, what I'm looking for is, what turbo size and trim do I get and turbo manifold.

P.S.Also, should I go with a external wastegate or stay with the internal?

Thanks,Jeramy

[Nameless EJ6]

I'd stick with a T3/T4 turbo so you can keep using the stock manifold. You probably want something with an A/R of about .63. A ball bearing turbo will give you the quickest spool up and best response.

I'd keep the stock exhaust manifold and adapt an external wastegate. Either an adapter box or have a flange welded onto the manifold.

[BoostFab]

i like to match an SC61 to the rb25...that turbo can put down serious power while not dramatic with lag on the 6 cylinder.

[Porschephile]

The Garrett Gt3071r sounds perfect for you. They're cheap at $1-1.3k, but good for up to 480rwhp. They have a t3 flange as well. I'm thinking of using one as a single on my rb26, since I don't have very large power goals.

[BoostFab]

The Garrett Gt3071r sounds perfect for you. They're cheap at $1-1.3k, but good for up to 480rwhp. They have a t3 flange as well. I'm thinking of using one as a single on my rb26, since I don't have very large power goals.

price vs power capable of the turbo...go with a garrett t3/t4 turbo or its derivative, ie; precision turbo or inovative. $1G is too much for a turbo that's rated under 500hp

[Imissmyturbo]

My personal experiance with my turbo:AGP T3/T4.60 AR compressor housing with GT40 56 trim wheel 65 lbs/minStandered bushing center housing..63 AR exhaust housing with a stage 5 exhaust wheel.I start to see boost around 3K in 3-5th gear and full boost is around 4KIt's a bit laggy but I don't mind. I am only running 12 psi right now so I am not using the turbo to it's half potenial.For better spool a 50 trim compressor with a stage III exhuast wheel would give you quicker boost. I would run it in an .82 AR exhaust housing.

[Wykid 240]

sorry, i haven't gottin back in awhile. but i've been in a family crisis. thanks for replies. . .

Imissmyturbo:how does it feel around town and have you dyno'd it yet?

[Imissmyturbo]

It's laggy but not that bad. It's more turbo then I will ever need. A 50 trim would probably be wiser but to make power with them you need run alot of boost. 15+ PSI.

[Wykid 240]

So, with a 50trim, when do you think it'll reach full boost?

Jeramy

[Imissmyturbo]

A 50 trim with a stage III wheel would probably make full boost around 3500 RPM's. I would get it with an .82 AR exhaust housing so it doesn't spool too quick and cause a sudden loss of traction.

[Joe]

A 50 trim with a stage III wheel would probably make full boost around 3500 RPM's. I would get it with an .82 AR exhaust housing so it doesn't spool too quick and cause a sudden loss of traction.

that could be aleviated with a good boost controller, something like the AVCR will let you input boost levels per RPM so you can control traction better, he seems really concerned with spool, i would go smaller than a .82 AR but match it with a great boost controller so you can help control wheelspin down low.

[Imissmyturbo]

The other thing with the .82 exhaust housing is you will get maximum flow out of the 50 trim compressor with it.