blackbird345

I know backpressure would be crazy but what if I used two wastegates? I would think that most of the exhaust would bypass the turbo anyway so would backpressure still be a big problem? I'm only looking to run about 9 psi with a 9.5:1 CR and a T76 (oncenter). Any ideas if this would work?

black98ws6ta

iTrader: (77)

Even at low boost that set-up would see tons of backpressure. I'd go with a different turbo kit, or a smaller motor if you absolutely have to stay with that turbo kit.

BoostnTBSS

iTrader: (-1)

Well it could work but that motor should flow about 72-74lbs @ 9 psi , and i dont have a flow chart for that turbo but prob flows around 35-40 lbs of exhaust so you would have a good amount of back pressure. but 2 44mmor bigger gates could help you out to make it work the goal is to to be a coulple lbs off like say it flows 72 + 9 psi = 81 the ex. flows 35 and say the gates flow 20 each for 40 that would be 81 intake and 75 ex that would be ok not perfect but close. well hope that helps

RealQuick

iTrader: (14)

Wastegates arent the issue with that kit. If backpressure/wastegates were the issue, you would have boost creep.

The problem is that when the intake sees the correct boost level (lets say 10psi) which means the wg is working as it should, the design of the kit itself (piping size and pass thru log) creates ~3:1 ratio of exhaust pressure. Your going to have large exhaust backpressure no matter what. This is independent of the wasteagate.

If the wastegate couldnt evacuate the gas quick enough, then you will see the intake boost creeping higher than the desired boost level during a pull. This of course means the exhaust backpressure is increasing as well.

Two different scenerios.

Ryan K

iTrader: (11)

Street kit is not the best option for a larger engine. The limiting factor on the street kit is the on-center exhaust housing.

Realquick has the right info for you, the only reason to go to a second or larger WG is Boost creep.

On the other hand, TTi's race kit would be fantastic for a 408...

blackbird345

Hey Guys thanks for the responses. So what if I used a midlength header on the passenger side, then a custom crossover with a WG on that, then standard WG by the log. This way there wouldn't be as much exhaust going thru the log either because as soon as the backpressure started to build up it would be passed through the WGs. Ok I know I'm missing something....

Ryan K

iTrader: (11)

Ok, I'll be more specific. TWO WGs WILL DO NOTHING FOR REDUCING BACK PRESSURE. TWO WGs would only prevent boost creep...

1CAMWNDR

iTrader: (21)

Don't do it. Get the TTi Race system, or have one built for your set up.

RealQuick

iTrader: (14)

Like Ryan said, forget the wastegates. The wastegates are controlled by the boost level it sees on the cold side (intake manifold pressure for example). Think of the TTi kit without wastegates at all... bloa\cked off flanges. Lets follow the path of exhaust from the pass. side. All is fine and dandy until it needs to pass thru the log where the driver's side exhaust is dumping. Due to the pass. side exhaust and driver's side exhaust having to squeeze thru the same pipe to get to the turbo (thats the goal to get exhaust to the turbo), then the pressure in the exhaust system spikes up. This will limit the max power output and may cause cracking issues in the log. You are probably goign to have serious backpressure with a 408ci.

BoostnTBSS

iTrader: (-1)

Well the waste gates flow exhaust and at a given boost they will lower the back pressure if you run 2 big ones. just think of it as adding a big dump pre turbo. once in boost it will lower back pressure. and who wants to lower it before boost it will spool better. ya its not the best way to do it but when on a buget it works and you will be happy with the out come.seeing as a 408 with 9 psi on a T76 should be about 700hp give or take.

blackbird345

BoostnTBSS I think I'll try it and let you know how it goes. The logic sounds good!

Ryan K

iTrader: (11)

Where is Carlos Mencia when you need him.

Dee Dee Dee...