Twin 38mm's over a single 44 on my pt88 setup?
09-30-2009, 11:44 AM
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Twin 38mm's over a single 44 on my pt88 setup? Trying to get my parts together now for my turbo build so I have a bunch of questions.... As far as boost control is concerned i've read on here that a 44mm wastegate won't be able to control boost well under 10psi on this turbo. I can get 2 38mm Tials for a really good price and my fab guy says they'd be easier to fit than a 60mm and possible control boost even better. Would this work well? Im looking to get down to around 6psi and I don't want to spend the money on a 44mm to have it not work, spike and break something. Has anyone used twin wastegates on single turbo before?
09-30-2009, 12:54 PM
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i have a T70 with a SINGLE 38mm. Only running 7.5 lbs. Holds boost perfect.
The key is where the wastegate is setup, and how easily your exhaust backpressure pre turbo will have access to escape through the wastegate. My Gate is about 3 inches upstream from my turbo, and is at a perpendicular 90* angle from the exhaust, but the upstream side of the pipe is cutout to a 45* for easy flow to the gate.
Have you ever seen how small the gates are on internally gated setups? They're like 25mm. But they're in the turbine stream. If you're as close to the turbo as you can get, you should be fine with a single.
Also, heat wrap helps too.
The key is where the wastegate is setup, and how easily your exhaust backpressure pre turbo will have access to escape through the wastegate. My Gate is about 3 inches upstream from my turbo, and is at a perpendicular 90* angle from the exhaust, but the upstream side of the pipe is cutout to a 45* for easy flow to the gate.
Have you ever seen how small the gates are on internally gated setups? They're like 25mm. But they're in the turbine stream. If you're as close to the turbo as you can get, you should be fine with a single.
Also, heat wrap helps too.
09-30-2009, 02:12 PM
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i have a T70 with a SINGLE 38mm. Only running 7.5 lbs. Holds boost perfect.
The key is where the wastegate is setup, and how easily your exhaust backpressure pre turbo will have access to escape through the wastegate. My Gate is about 3 inches upstream from my turbo, and is at a perpendicular 90* angle from the exhaust, but the upstream side of the pipe is cutout to a 45* for easy flow to the gate.
Have you ever seen how small the gates are on internally gated setups? They're like 25mm. But they're in the turbine stream. If you're as close to the turbo as you can get, you should be fine with a single.
Also, heat wrap helps too.
The key is where the wastegate is setup, and how easily your exhaust backpressure pre turbo will have access to escape through the wastegate. My Gate is about 3 inches upstream from my turbo, and is at a perpendicular 90* angle from the exhaust, but the upstream side of the pipe is cutout to a 45* for easy flow to the gate.
Have you ever seen how small the gates are on internally gated setups? They're like 25mm. But they're in the turbine stream. If you're as close to the turbo as you can get, you should be fine with a single.
Also, heat wrap helps too.
09-30-2009, 02:32 PM
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i have a "smaller" turbo compared to what most LS1 guys use. Only a T70. .82a/r turbine, so it doesn't let a whole lot of exhaust through, and i imagine i have alot more back pressure than larger turbo guys. SO... maybe that's why my smaller gate is ok? more backpressure means more air goin out of the Gate? But i'm at low boost also~ I'd imagine a 5.7L LS1 both pushing 8 lbs would have about the same amount of exhaust gas if at the same boost pressure, but then a bigger turbo has more air per psi... Eh, i give up tryin to explain hahahaha
my setup works for me, just sharing. t70 turbo with a single 38mm gate right next to the turbo.
my setup works for me, just sharing. t70 turbo with a single 38mm gate right next to the turbo.
09-30-2009, 02:50 PM
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Well my 6.0/T88 on 6psi would be flowing a lot more air than your setup on the same boost level(what goes in has to come out) and that 38mm would not be able to bleed off all the pressure needed to get the boost down to where id want it.
09-30-2009, 03:37 PM
#7
I will be using one on each side on the merge pipe right under the turbo..someone else here used a 44 on his t88 and was having boost creep problems...I just dont want to be stuck in that situation.Also on internally gated turbos..like my brothers in his evo..the lowest boost setting is 18psi. You have to remember Im trying to bleed off A LOT of exhaust to keep the boost down...its not like on the smaller turbos with more boost.
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09-30-2009, 04:31 PM
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(not in my pic, i've since changed it)
also WHERE you get your boost referance from is VERY important. I get mine right off the manifold Post throttlebody. Where the stock PCV goes back into the Intake. (i eliminated my pcv)
10-02-2009, 10:13 AM
#11
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If you can get (2) 38mm tials at a good price then go that route. Running two is like having a big safety net. If one fails you'll still have the other one to keep the boost down.
