Backpressure - Can big wastegates help?
Staging Lane
Joined: Sep 2008
Posts: 99
Likes: 0
From: MI
Drive pressure is related to boost pressure. To reach a set boost level, drive pressure must be what ever it is, to reach that. A wastegate regulates drive pressure, yes, but it still takes X drive pressure for the compressor to reach X boost level. Decreasing drive pressure by way of wastegate, only decreases boost level.
So they had the WG wideopen and still couldn't get the pressure out. LOL. Riiiiiiiiiiiiiight.
My guess would be that they were doing some sort of antilag, 2 step spool helper type activity with that noid.
Joined: Nov 2001
Posts: 8,484
Likes: 0
From: Cecil County Raceway!!!
So i should run a 38mm gate then!!! oh wait i can't cause i will get too much back pressure and boost creep!!!!I am not saying it is a cure but its a small factor!! all the other things add up like you said Lou.. if a ex housing flows 70lbs and a motor pushes 100 lbs there will be back pressure. now with a 38mm gate once open lets say it flow 15lbs and a 60 can flow 25lbs its a small factor. cause most run the gate back into the ex..
i guess we can all sell our big gates and run internal gates to save money....
i guess we can all sell our big gates and run internal gates to save money....
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
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 The manifolds and the complete exhaust are wrapped up real well.... some of it is double wrapped. The exhaust is 2.5" duals all the way to each turbo in the rear. I was wondering what effect spool would have if i downsized the exhaust to 2 or 2.25 duals to the turbo's?
On my 450+" LS motor, we're going to continue to use a 2.5" tube between the header and turbo feeding a 3.5" tube into the turbo. Game plan is to make well into the 2xxxhp range, or enough hp to go 175-180mph to the 1/8 mile.
On your car it would be interesting to see how a set of 1 5/8" stepped to 1 1/2" somewhat equal length headers would work.
great info phil, i may try to decrease the size of the rear section (over the axle) exhaust that bolts to the turbo to see if it spools quicker. If that works, i'll keep working towards the motor to see if i can improve it even more. Thanks!
Wow, you are going to be flying!! You are an asset to the board, thanks for the help! tracy
Basically your transporting the air from the end of the header to the inlet of the turbo, the smallest point in the exhaust is still going to be the turbine housing. I do not think that 2" tubes between the header and the turbo would hurt performance. On a 370" at 20# of boost you would see a max air speed of 550cfm which is in the acceptable area. It would probably spool faster also.
Last edited by TracyRR; Dec 21, 2010 at 01:47 PM.
Basically your transporting the air from the end of the header to the inlet of the turbo, the smallest point in the exhaust is still going to be the turbine housing. I do not think that 2" tubes between the header and the turbo would hurt performance. On a 370" at 20# of boost you would see a max air speed of 550cfm which is in the acceptable area. It would probably spool faster also.
.
.
it would be good logic if you had completely straight exhaust pipes, but with every bend in your exhaust your increasing restrictions, so even with lets say the smallest area in the turbine is 1.5" then a 15ft of 2.5 pipe with 3-4 90 degree bends would flow about equal of 1.5" restriction in the turbine, now if you have 2" pipe with your just adding more restrictions with every bend decreasing flow before you even get to the main restriction
now this is just an example
(if i was at work i have actually flow charts for pipe and bends and etc..)
in my opinion it would be best to keep the 2.5 pipe
i somewhat disagree with this
it would be good logic if you had completely straight exhaust pipes, but with every bend in your exhaust your increasing restrictions, so even with lets say the smallest area in the turbine is 1.5" then a 15ft of 2.5 pipe with 3-4 90 degree bends would flow about equal of 1.5" restriction in the turbine, now if you have 2" pipe with your just adding more restrictions with every bend decreasing flow before you even get to the main restriction
now this is just an example
(if i was at work i have actually flow charts for pipe and bends and etc..)
in my opinion it would be best to keep the 2.5 pipe
it would be good logic if you had completely straight exhaust pipes, but with every bend in your exhaust your increasing restrictions, so even with lets say the smallest area in the turbine is 1.5" then a 15ft of 2.5 pipe with 3-4 90 degree bends would flow about equal of 1.5" restriction in the turbine, now if you have 2" pipe with your just adding more restrictions with every bend decreasing flow before you even get to the main restriction
now this is just an example
(if i was at work i have actually flow charts for pipe and bends and etc..)
in my opinion it would be best to keep the 2.5 pipe
because if its a front mount there is a lot more variables involved ( such as heat, density and velocity ect..)
with rear mounts i do see flow restrictions being a problem
but i doubt your doing a rear mount and trying to make 2800 hp
is it going to be a rear mount?
because if its a front mount there is a lot more variables involved ( such as heat, density and velocity ect..)
with rear mounts i do see flow restrictions being a problem
but i doubt your doing a rear mount and trying to make 2800 hp
because if its a front mount there is a lot more variables involved ( such as heat, density and velocity ect..)
with rear mounts i do see flow restrictions being a problem
but i doubt your doing a rear mount and trying to make 2800 hp
TECH Apprentice
Joined: Mar 2006
Posts: 361
Likes: 1
From: australia
Basically your transporting the air from the end of the header to the inlet of the turbo, the smallest point in the exhaust is still going to be the turbine housing. I do not think that 2" tubes between the header and the turbo would hurt performance. On a 370" at 20# of boost you would see a max air speed of 550cfm which is in the acceptable area. It would probably spool faster also.
On my 450+" LS motor, we're going to continue to use a 2.5" tube between the header and turbo feeding a 3.5" tube into the turbo. Game plan is to make well into the 2xxxhp range, or enough hp to go 175-180mph to the 1/8 mile.
On your car it would be interesting to see how a set of 1 5/8" stepped to 1 1/2" somewhat equal length headers would work.
On my 450+" LS motor, we're going to continue to use a 2.5" tube between the header and turbo feeding a 3.5" tube into the turbo. Game plan is to make well into the 2xxxhp range, or enough hp to go 175-180mph to the 1/8 mile.
On your car it would be interesting to see how a set of 1 5/8" stepped to 1 1/2" somewhat equal length headers would work.
phil,
are you saying your going to step the headers from 1 5/8 down to 1 1/2 , before the collecter ?
TECH Apprentice
Joined: Mar 2006
Posts: 361
Likes: 1
From: australia
