wastegates - dual 38mm or single 44mm?

[boostedEG]

ok so my old setup was seeing a little boost creep, and thus i sold my manifold and will be making a new one soon, but want some opinions on wastegates

the motor is a GSR w/ a 60-1/t3 on it and im looking to make around 450-500hp.

i had a topmount with a single 38mm on it, and it was set at 15 psi, however it would creep up to almost 20 psi.

for the new manifold im debating between a single 44mm and twin 38mm's. i know either way i shouldnt have any creep issues, but both setups will cost about the same. so what are some pro's and con's of each?

i have heard that with two wastegates it can have problems holding boost as even when the valves only open a tiny bit it lets a lot of exhaust gases out... however i also know jeremy (servion) was/is running twin 44's, as do lots of people with high HP setups.

[john]

I'd do a single large valve part.

[60-1teg]

just dont put one on then you dont have to worry about it creeping

[nicklk]

What top mount do you have? Location of wastegate can play an important part on boost creep, as well as your dump....

[fusionsport]

what boost are you trying to run on which turbo? Trying to run an absurdly low amount of boost on a large turbo is not only stupid, its an exercise in madness. One large WG should do the trick, assuming it is operating properly on a proper manifold. I used a Turbosmart 35mm gate on my SC61 T3/4 and I could run as low as 12psi if I wanted, which I never did.

[marcrx5]

What top mount do you have? Location of wastegate can play an important part on boost creep, as well as your dump....

Agreed, I think the placement is the biggest problem, not the wastegate. Even still, I'd run a single 44mm. The only reason I'd ever run dual wastegates is on a twin scroll setup, and even then there are ways around that.

[STIBungy]

38mm is a bit small for that size turbo.

[nicklk]

what boost are you trying to run on which turbo? Trying to run an absurdly low amount of boost on a large turbo is not only stupid, its an exercise in madness. One large WG should do the trick, assuming it is operating properly on a proper manifold. I used a Turbosmart 35mm gate on my SC61 T3/4 and I could run as low as 12psi if I wanted, which I never did.

I ran a 57 trim t3/t4 on 8psi and didnt have a slight issue with boost creep on an equal length with a 35mm Tial, but my wastegate was located directly in the center of all 4 runners...

38mm is a bit small for that size turbo.

I've ran many sc61's with 38mm's up to 28psi with no issues?

[sbiggi]

Placement of the wastgate and how low of boost you want to run are the main issues.

Sounds to me that your current setup doesnt have the wastgate placed very well.

[60-1teg]

38mm is a bit small for that size turbo.
a friend and i both run tial 38mm gates and we both run Precision Pt67 T4s never had a problem yet.he makes 651 i made 583 i was never really worried about it creeping though

[servion]

The reason I went to dual gates is because I switched to a twinscroll turbo and manifold, and the proper way to regulate that is to have a gate for each pair of runners. I used to run the old t3/t67 (.63 hotside) with a tial 35 at 10psi all day without any problems. The main thing is, will the exhaust want to make the turn to leave through the wastegate instead of passing through the turbo istelf?

2 questions:
1) How big (or non-restrictive) is your downpipe, exhaust, dumptube. Also, what turbine housing and turbine wheel are you using?

2) What boost controller are you using? I've had customers who have had nasty boost creep and was actually jsut aboost controller setup related issues.

[STIBungy]

Mmmmm, twin scroll.

[boostedEG]

I ran a 57 trim t3/t4 on 8psi and didnt have a slight issue with boost creep on an equal length with a 35mm Tial, but my wastegate was located directly in the center of all 4 runners...



I've ran many sc61's with 38mm's up to 28psi with no issues?

the .57 trim is a small-ish turbo, and the SC61 was on higher boost so i wouldnt expect you to have issues.

What top mount do you have? Location of wastegate can play an important part on boost creep, as well as your dump....

the WG was placed on the collector immediatly before it entered the turbo. and it dumped to atmosphere.

what boost are you trying to run on which turbo?

60-1/t3, and i want to run the most boost i can safely run on pump gas....
i figure thats in the ballpark of 15-20 psi. and it was creeping at 15psi before.

i will turn it up higher on E-85

a friend and i both run tial 38mm gates and we both run Precision Pt67 T4s never had a problem yet.he makes 651 i made 583 i was never really worried about it creeping though

yeah but you and topher were both running high boost.... when your forcing all the exhaust gases through the turbo to make that high boost you barely even need a WG.

2 questions:
1) How big (or non-restrictive) is your downpipe, exhaust, dumptube. Also, what turbine housing and turbine wheel are you using?

2) What boost controller are you using? I've had customers who have had nasty boost creep and was actually jsut aboost controller setup related issues.

it was a 3" open DP, im thinking bout bumping it up to a 3.5" full exhaust, not not sure if i actually need that.
t3 .63 A/R housing w/ stage 3 wheel

at the time there was no boost controller, but i do have a turboXS manual boost controller i plan to use.

[60-1teg]

the .57 trim is a small-ish turbo, and the SC61 was on higher boost so i wouldnt expect you to have issues.



the WG was placed on the collector immediatly before it entered the turbo. and it dumped to atmosphere.



60-1/t3, and i want to run the most boost i can safely run on pump gas....
i figure thats in the ballpark of 15-20 psi. and it was creeping at 15psi before.

i will turn it up higher on E-85



yeah but you and topher were both running high boost.... when your forcing all the exhaust gases through the turbo to make that high boost you barely even need a WG.



it was a 3" open DP, im thinking bout bumping it up to a 3.5" full exhaust, not not sure if i actually need that.
t3 .63 A/R housing w/ stage 3 wheel

at the time there was no boost controller, but i do have a turboXS manual boost controller i plan to use.
no work tomorrow?

[boostedEG]

i dont know if it matters or not but it only had creep in 4th and 5th gear. i assume thats because since it had traction isssues in 1-3 the motor wasnt being loaded enough to creep.

[boostedEG]

no work tomorrow?

yeah, why?

[60-1teg]

yeah, why?
what the fuck are you still awake for?i thought you went to bed at 9?

[boostedEG]

naw im usually up late... thats why im always late for work

[boostedEG]

so is twin scroll some new technology, or is it the same thing as the divided housings that have been around for a long time?

[STIBungy]

Been around for a long time. Subaru and Mitsubishi have used them. I believe the current gen EVO uses a twin scroll turbo.

so is twin scroll some new technology, or is it the same thing as the divided housings that have been around for a long time?

[boostedEG]

but is twin scroll the same thing as a divided housing?

[Mark_H]

I wanted to throw my worthelss .2 cents in here. FWIW I had a crappy Ebay manifold that was known for massive boost creep. I ran a Garret t3/60-1 with a .63 exhaust and .70 cold side. I ran a Tial 38mm wastegate with a 14psi spring and no boost controller and it held 14psi almost perfectly in every gear.
Also, this debate had been brought up several times on a bunch of boards and I remember there was an article on Tial's website(can't find the article now) that basically states "bigger isn't always better" and that the 38mm wastegate actually supports more boost then we all for no particlular reason tend to think.
HTH
Mark

[john]

I believe so. The header exit is divided as well, so pulses into the divided turbine housing are alternated.

but is twin scroll the same thing as a divided housing?

[ComputerJLT]

i've heard twin scroll and divided used interchangably so i'd say they were the same.

But to answer your question, two 38mm gates will have MUCH more area to let off exhaust compared to one 44mm; it's not about surface area its about how much of the valve is facing the outlet; obviously you get a lot more with two smaller gates compred to one slightly bigger.
Now with that said you do get some flow out of the sides and back of the valve but the majority is going out at the point where the gate opens.

Personally i'd go dual gates because one, the chinese gates are cheap and two wastegates just look menacing!

And of course the split/twin scroll housings they dont NEED two wastegates but it helps.

Lastly if you run a tiny turbine housing to get fast spool you'll want more wastegate so that you dont have as much exhasut restriction. Somewhere on honda-tech a guy went from a .82ar stage 5 turbine to a .48 ar stg 5 with two wastegates, he lost a little top end but the turbo spooled like 2000 rpm sooner. I think this was a road race setup so the sooner the turbo comes on the better; it may still be on h-t somewhere.

[boostedEG]

alright, well thanks for the input. i think im gonna stick to 1 WG for now... but i might try a single 38 again, and if i have issues just change the flange to a 44.

[daBoosted93]

well i have a 50 mm wg that you can try!