Re: Unusual boosting problem
 

like chris and the other guys said. even a non stock exhaust is way restrictive. especially with a cat .

Re: Unusual boosting problem
 

try pulling the boost reference to the wastegate and see if you can bring it past 10psi then.

Re: Unusual boosting problem
 

never thought of that ::)

Re: Unusual boosting problem
 

with everything you've done it sounds like a torn coupler or cracked/punctured fmic or bad weld somewhere that's losing/leaking boost somewhere.

are you using a coupler that seemed very loose going on and possibly leaving a slight crease when tightening? i had a customer that had a coupler that was slightly loose on a straight coupler and really needed a transition coupler to be sealed tightly.

Re: Unusual boosting problem
 

See something like that would cause the boost to build VERY slow. You would definatly know the difference between a potential leak and an issue like this one. If it's really laggy and building boost slow this may be the case, otherwise I doubt it's a leak and thusly I'm clueless. Pulling the WG line was my suggestion and you already did it. :-\ Good luck.


JP

Re: Unusual boosting problem
 

Thanks guy's. Yeah we pulled the wastegate line just as a test and it still was limiting it's pressure. The wastegate was swapped after that and it did the same thing. We had this car on the dyno (before we realized there was a boosting problem) and it seems to build boost normally. Not slow at all. If anything it will build up to about 11-12 psi and fall back to 10. Almost like the exhaust gasses arent strong enough to spool the turbo up anymore but I know that can't be. The owner tried 2 different turbo's with the same results. Checked the engines compression and it's 150 accross the board (8.5:1 pistons). Very strange problem. I'm almost starting to think there could be valvetrain issues. Or I don't think he's running a catch can, is there a possibility the boost is blowing by internal parts of the engine?

Re: Unusual boosting problem
 

sounds restricted to me, exhaust or in intake flow.

Re: Unusual boosting problem
 

I'm going with exhaust too. That was the problem on my friend's hatchback LS/14b. Wouldn't boost past 10-12psi and when we took the exhaust off and ran it open downpipe the sucker would rip up to 16+psi with no issues.

Re: Unusual boosting problem
 

it doesnt sound to me like its a leak problem due to the boost just stopping at ten
if it was a leak then it would just build slower than it should
but you really have me stumped
have you checked out the guage maybe try a different gauge
mite be as simple as that it is boosting but you dont know it

Re: Unusual boosting problem
 

Yeah the boost guage was checked out and another one was put in it's place to test it out. He also tried eliminating the intercooler by running a pipe from the turbo to the intake manifold and it's still holding at 10 psi. So that tosses the Intercooler out the window. The only other thing it could be is the exhaust :-\... He's going to try and run an open downpipe to see if that changes anything.