Forced Induction Superchargers | Turbochargers | Intercoolers

3", 3 1/2" or 4" pipe to turbo?

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Old Jun 3, 2005 | 07:37 AM
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Default 3", 3 1/2" or 4" pipe to turbo?

I'm still in the planning of my turbo install, shooting for ~700fwhp from my 355. Its going to be alky injection and intercooled because of the 10.5:1 here are the rest of the specs.

355 sbc
forged bottom
230/244 hyd flat cam ( i know its not perfect, but we'll see how it does)
1.6 RRs
ported Gm 441's (284/237 @ .600")

currently pushing ~430-440 fwhp. I plan on a rear mount t70 turbo (.84 A/R) wrapping to about 6800-7000rpm. Estimating 10-12 psi. I'm going to go 3" from the headers to a Y, then to the turbo. Should i go 3, 3 1/2" or 4" to the turbo?
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Old Jun 3, 2005 | 07:46 AM
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Originally Posted by menlatin
I'm still in the planning of my turbo install, shooting for ~700fwhp from my 355. Its going to be alky injection and intercooled because of the 10.5:1 here are the rest of the specs.

355 sbc
forged bottom
230/244 hyd flat cam ( i know its not perfect, but we'll see how it does)
1.6 RRs
ported Gm 441's (284/237 @ .600")

currently pushing ~430-440 fwhp. I plan on a rear mount t70 turbo (.84 A/R) wrapping to about 6800-7000rpm. Estimating 10-12 psi. I'm going to go 3" from the headers to a Y, then to the turbo. Should i go 3, 3 1/2" or 4" to the turbo?
Supposedly a 3" pipe will conform to the correct shape of a T4 flange, so the hot side (if it were me) would enter the turbo using a 3" pipe. You can run what ever you want all the way down, but i'd transition to a 3" piece right at the T4 flange.
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