Unusual boosting problem
 

Hey guy's I know we alway's hear the same "Why's my car not boosting" questions, but this one really has me clueless... It's a built H22 boosted setup that does build boost, but it WILL NOT boost past 10lbs. As soon as it reaches 10psi it just stay's there as if something's not allowing the turbo to build boost past that point.
With help from myself and many others, the owner has tried everything to solve this problem. We've checked the timing, swapped camgears, checked for boost leaks, checked and swapped boost guages, swapped intake manifolds, swapped exhaust manifolds, Swapped 3bar MAP sensor's, swapped wastegates, swapped turbo's, double and triple checked the tuning, swapped blowoff valves, swapped throttlebodies... Everything... We even got daring enough to unplug the wastegate line to see if it would boost past 10psi, and it would not. This one really has me confused fellas, any thoughts as to why the setup or engine might be doing this?

Re: Unusual boosting problem
 

shitty bov?
shitty turbo?

Re: Unusual boosting problem
 

Well, the blowoff valve was replaced as was the turbo with a brand new T3/T4. Neither solved the boost issue so the Garret 60-1 was put back on.

Re: Unusual boosting problem
 

exhaust?

Re: Unusual boosting problem
 

If all the mechincals are there and working, obivously something is up with the charge piping

Why it would constantly hold 10psi I dunno though

Re: Unusual boosting problem
 

run that bitch open down pipe, report back.

Re: Unusual boosting problem
 

Put a pipe in place of the FMIC. report back. That solved jordans low boost problems.

Re: Unusual boosting problem
 

shitty IC maybe

Re: Unusual boosting problem
 

Could have pressure drop through the IC... also, like they said... what about your exhaust? Is it restrictive?

Re: Unusual boosting problem
 

Well, those are some definate possibilities. I know it's not the factory exhaust... I think it's a Thermal setup but I can't be sure at the moment. It is definately a strange problem, I've never seen a car only build a certain ammount of boost and the poor owner has gone through EVERYTHING to figure it out. The IC could also be questionable. Maybe as stated above by running a straight pipe and eliminating it (for testing) that could be the problem.
Any more thoughts fellas? I do appreciate this, I had started running out of ideas myself.
Steve

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.

Re: Unusual boosting problem
 

I see you have tried all sort of things already. Did you try a different tuning program? There might be a glitch in the current program that is activating boost-cut.

Re: Unusual boosting problem
 

I have seen this happen before...but usually the boost cut feels very violent, like a rev limiter. He would probably notice that.

Re: Unusual boosting problem
 

Did he ever drop the exhaust. Its usually the simpliest thing if the motor is healthy etc

Re: Unusual boosting problem
 

Do u have any filter ? ::)