408 ci with TTi street kit?
Thread Starter
TECH Apprentice
Joined: Sep 2005
Posts: 344
Likes: 0
408 ci with TTi street kit? 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?
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
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.
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.
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...
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...
Thread Starter
TECH Apprentice
Joined: Sep 2005
Posts: 344
Likes: 0
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....
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Originally Posted by 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....
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.
