Turbo experts please.
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 948
Likes: 0
From: orlando, florida
Turbo experts please. I've been racking my brain trying to figure out why my car won't hold boost. I know that the turbo i have now is way to small(thats is getting fixed real soon 
). But i'm getting mixed opinions on wether or not to small of a turbo will lose boost on the top end. I,m running 13psi right now and at about 4000rpm my boost starts droping off to 9.5psi and holds that to 6500rpm. What do you think this is caused by? No matter what boost I try to run it always dropes off to 9.5psi. I've checked my wastgate it seems fine. I've checked all the piping no leaks. BOV seems to be functioning properly and the wastgate signal is coming from the intake. any thoughts will be appreciated. Thanks.
). But i'm getting mixed opinions on wether or not to small of a turbo will lose boost on the top end. I,m running 13psi right now and at about 4000rpm my boost starts droping off to 9.5psi and holds that to 6500rpm. What do you think this is caused by? No matter what boost I try to run it always dropes off to 9.5psi. I've checked my wastgate it seems fine. I've checked all the piping no leaks. BOV seems to be functioning properly and the wastgate signal is coming from the intake. any thoughts will be appreciated. Thanks. Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 948
Likes: 0
From: orlando, florida
Yea I tryed mounting the gate on the log like QMP, Didn't work, in fact it wouldn't hold more then 8psi like that. So i mounted it kind of in the original location but it's positioned so the exhaust gases can exit easier. George thinks it might be caused by excesive backpressure I have one of the first design TTi logs that used the 2in I.D log and 1.5in primarys. I'm thinking once I get the new turbo if i'm still having this problem maybe i'll try getting the bigger log from George to see if that helps. Thanks guys.
It can only be 1 of two things, either the backpressure is to great and is forcing the wastegate spring open, or the turbo is starving for air. More then likely its the turbo. Trying the larger manifold is not a bad idea though, 346ci's flowing through only 2"'s is not very good flow wise.
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 948
Likes: 0
From: orlando, florida
What do you mean by the turbo is starving for air? Are you saying that it's to small or that the air filter/inlet piping are to restrictive?
If the backpressure is forcing the wastgate open would it still reseal at 9.5psi and hold that boost level? Thanks i appreciate all your help guys!
If the backpressure is forcing the wastgate open would it still reseal at 9.5psi and hold that boost level? Thanks i appreciate all your help guys!
did we go over what wg spring you had? if its the origninal 5# or whatever spring then thats your problem.. if you're tune is along enough to run 10psi on pump gas then go ahead and invest in a 10# spring.
on the revised set up for the street kit george mounted the wastegate on the passenger side right after the manifold on the crossover.. i imagine he would reccomend you try that or even put a second one there.
on the revised set up for the street kit george mounted the wastegate on the passenger side right after the manifold on the crossover.. i imagine he would reccomend you try that or even put a second one there.
Trending Topics
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 948
Likes: 0
From: orlando, florida
The spring i have in there now is a 7-9psi spring but i have a manual boost controler also. Kinda funny how the boost drops off to the spring rating? Maybe i'll try to find a stiffer spring. Whats the next couple size up springs?
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 Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 948
Likes: 0
From: orlando, florida
I removed the MBC last night and cranked the adjuster screw in on my wastegate to see what would happen got it up to 11psi but it still just droped off to 9.5psi. I'm going to try and find a stiffer spring this week see if that helps any.
I was wondering, where can you get these springs for the delta gate?
I have looked and everyone that I hve found wants to sell a complete set of springs for like a bill, anyone know where you can buy them indivifually?
thanks
ed
firebird455@onebox.com
I have looked and everyone that I hve found wants to sell a complete set of springs for like a bill, anyone know where you can buy them indivifually?
thanks
ed
firebird455@onebox.com
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 948
Likes: 0
From: orlando, florida
Any turbonetics dealer should be able to hook you up with a spring i bought an assortment of three spring from a local dealer for $20. I'm going to go back there monday to have them find me a 11-13psi spring.
Pull the wastegate, slide a piece of sheetmetal in between the WG and the flange to block it off,and bolt it back together. Then take it for a spin to eliminate the wastegate from the situation altogether.
Just make sure you've got good gas in the tank in case the boost momentarily goes higher than you anticipate.
Just make sure you've got good gas in the tank in case the boost momentarily goes higher than you anticipate.
Registered User
Joined: Jun 2002
Posts: 453
Likes: 0
From: Forced Induction Heaven
Originally Posted by JZ 97 SS 1500
Becareful with that test. You will see some BIG boost if you block the WG hole.
Jose
Jose
Since your Wastegates are external that solves the disruptance that occurs when the wastegate opens...internal wastegates disrupt the flow and cause the turbine to slow down...then boost will dorp.
You should really measure the backpressure...A Turbonetics 60-1 can move enough air to supply 600hp.
http://turboneticsinc.com/compressor.html?comp=60-1
Also the down pipes are only 2"...that is rediculous.
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 948
Likes: 0
From: orlando, florida
I did a back pressure test awhile back and back pressure was pretty high. I think it was 28psi @ 10PSI boost so almost a 3-1 ratio. But that was with a 2.5in down pipe. now i'm running a 3in down pipe so that should help some. But my log manifold is still 2in so i think a majority of my back pressure issues are coming from that. When i was running the WG venting to atmosphere I could here the WG when it opened up but when my boost started falling the WG would remain open, shouldn't the WG close to try and hold the set 13psi. Thanks.
If you block off the wastegate and take it for a drive, youll be able to isolate the problem. If you hit the gas and see the boost gauge pass the 9.5 mark or wherever youre stuck at, then back off because you've identified the wastegate as the problem from opening too much under pressure.
If it doesnt change a bit at WOT then youre out of turbo.
Like I said, just have race gas in the tank is case the boost jumps up faster then you can react to close the throttle.
If it doesnt change a bit at WOT then youre out of turbo.
Like I said, just have race gas in the tank is case the boost jumps up faster then you can react to close the throttle.