Can Not keep boost past 11

[Quicksilvergsx]

My boost will spike to between 14 and 20psi depending on where I set my MBC, then almost always slowly return to 11 -10 psi.


I just got done doing a boost leak test
results: Went to 20 psi then slowly dropped to 0 but took well over 30 seconds so I assume it is ok.

I also moved my mbc from tapping into the bov line to the compressor. It did not change anything.

I was just wondering what I need to check or what you think the problem could be.

thanks
Matt

 

[kelvinb]

first off, where is it leaking from? is it your bov or somewhere else? were you testing from the turbo? do you notice black smoke when you are only getting around 10-11psi? does it seem sluggish?

 

[Amazin' Wasian]

Do a boost leak test, also check all your lines off your MBC the smallest rip or cut in the line could mess up your boost.

-nick

 

[Quicksilvergsx]

Kelvinb wrote:

"first off, where is it leaking from? is it your bov or somewhere else? were you testing from the turbo? do you notice black smoke when you are only getting around 10-11psi? does it seem sluggish?"

When I did the boost leak test I did NOT hear any leaking sounds. I thought holding boost for over 30 seconds was a sign of having virtually no leaks. Am I right with this? I did test from the turbo. I also did not notice any black smoke, and the car did not really seem sluggish. (when I hit 16 psi on a spike it really felt like 16 psi)

Do a boost leak test, also check all your lines off your MBC the smallest rip or cut in the line could mess up your boost.

Did a leak test and all of my lines are good.

 

[zippyshoe]

Based on your vehicle profile, it looks like you still have the stock T-25 turbo - what you may be seeing is normal for this turbo. If the boost is falling-off to 10-11 psi at high rpm's (above about 5K), then you are probably seeing a normal response from your turbo. The T-25 does not have sufficient airflow capacity to maintain higher boost levels than about 10-11 psi at high rpm's. There is nothing your boost controller can do to compensate for this limitation of the T-25. To maintain higher boost levels all the way to redline, you will need to upgrade your turbo.

 

[Quicksilvergsx]

If the boost is falling-off to 10-11 psi at high rpm's (above about 5K), then you are probably seeing a normal response from your turbo

I doubt this is the problem since in the past the car has held 16 psi with no problem.

I have also noticed that sometime it will hold boost just fine and other times it won't.

My exhaust is sealed with no leaks, but seems to be loose somewhere and rattleing around pretty loud around 3500 rpms. Could this possibly cause the knock sensor to pick the sound up making my boost drop? I really assume it is my exhaust making this noise. It seems like when that sound isn't there my boost will stay were I want it. Obviously I will need to check all these things, but I am unable for a few days.

Anyone had any experience like this? Is this possible?