CHAMRA1

Hi Guys
I have a 408 Twin Turbo Ls1 Auto .

I'm running a Twin Garrett GT35 Turbos , With Twin external Tial 38mm Wastegates .

Both wastegates get their boost reference from the same source , Just before the Throttlebody .

I'm at a delama as what Wastegate springs to use ?
And have been argueing with my tuner because of this .

I want to run 14 pounds boost total .

From my understanding I need 14 pound springs ( Big Blue Springs) in each wastegate , And I will get constant 14 psi boost ,
Remember Both wastegates are referenced from the same boost source .

My Tuner says No , You need 7psi springs each wastegate and you will get 14 pounds total .ANd if I use 14 pound springs you will end up with 28 pounds boost .
I should add this is my tuners first Twin Turbo Car he's tuned .

Which way is the right way ?
2 x 7 pounds springs ? or 2x 14 pound springs ?

I also want to run a AVC-R Boost controller , Using one soleniod , Is this possible ?

Say set it to 1 bar pressure and 30% duty cycle . I should get reliable boost curve ?

CHAMRA1

If anyones interested .

The cars a Commodore .

Motor is a 408 cube lq9 with AFR 225 Heads ,
Eagle Internals , Diamond Pistons 9.5:1 comp .
Pac Dual Springs Titanium retainers etc .
T&D Shaft Rockers , Comp Cams Lifters .
LS2 Intake with 90mm Nick Williams TB .
-
Exhaust manifolds are 4-1 Merge collecters with 3" dump pipes and a 38mm Tial Wastegates .
All has been Ceramic coated Black .Including turbine housings .

Exhaust is Twin 3" all the way .
Cooler size is 600mm x300mm x 4" thick

HydroStream6

iTrader: (16)

Get a new tuner. You are correct.

Just keep in mind with 14psi springs you won't be able to run any LESS boost than 14psi. Your spring is always your minimum allowable boost pressure. The up side to that is they won't blow open as easy as the 7psi springs would. But year, for 14psi, use 14psi springs.

black98ws6ta

iTrader: (77)

Agreed.

RealQuick

iTrader: (14)

+1

Orr89rocz

iTrader: (13)

Agreed. You can run 7 psi based springs and a boost controller to get 14 psi. Thats what I do. I found with my JGS wastegates and the factory installed 6-7psi springs, I see about 8.5 psi at the intake. Probably because the wastegates are only fed by 2 cylinders on the manifold really...

If you have a good wastegate location, and less restricted exhaust for lower overall backpressure, you should see 7psi for 7psi springs. A simple manual controller will bump up to 14 psi.

that way you can tune at 7 psi and slowly dial it in up to 14psi.

bigti99a

iTrader: (16)

jesus, that looks like a tight fit!! and i agree that on a build like this i would like a tuner who has done many before playing with my car.

onfire

iTrader: (17)

"I also want to run a AVC-R Boost controller , Using one soleniod , Is this possible ?
"

I would not hit a dog in the *** with a AVC-R Apexi.

BLINGOLE

iTrader: (5)

Seriously?! Dam that's what I got on my turbo build! Why have had a bad experince or something?

TurboAv

iTrader: (6)

Back in 02 when the WRX was first released I bought one. Then started modding it. An AVC-R went on. I was always having overboost issues when I downshifted and hit it. One night I saw a 25psi spike and my motor grenaded. AVC-R = Never again!

onfire

iTrader: (17)

I went through three of the POS. Each one would work well for a week or 2 and then start overboost, etc. One fella lost an engine due to it overboosting....unit display gets very hot when on....I think the heat messes with the internals.

MaxxMitchell

iTrader: (15)

Does it work?

3800SII

Can I hijack this thread and ask if the same concept would apply to a twinscroll turbochager with two 44mm wastegates? I cant determine whether or not to use two 7psi springs or two 4 psi springs. I want a max of 8lbs of boost. Not going to use a boost controller either, but each refernce signal will come directly from the manifold.

slow67

iTrader: (2)

7 PSI springs. otherwise at 4PSI both gates would be open. Either that or get 4 PSI springs and a boost controller.