Lost Boost! Can't figure out why.

[Catbox_95]

I am running a Garrett T3/T4, Tial 35mm wastegate, GReddy BOV, plus other mods. I usually run around 21 psi, and things have been fine. Then the other night, I only hit 17 psi, so I gave it another run and only hit like 13 psi. I pulled over and couldn't find the problem.

The wastegate is not opening. If I set my boost controller at 11 psi, I hit 11 psi and the wastegate opens. It is obvious when it opens because it dumps to the atmosphere and is loud. So, if I set my boost controller above 13 psi, the wastegate never opens and the boost never goes past 13 psi.

Also, the boost sounds have changed. It used to boost very quickly, then dump the wastegate open, then when I would let off to shift it would do that "chirp chirp" sound. Now that sound is totally gone. Here is a video of my run at the track with the sound between shifts that I'm talking about:

Click Here

I don't find it a coincidence that I lost the ability to boost along with the blow off sound I'm used to hearing. The turbo is spinning freely just fine, as I can see it when I remove my air cleaner. No boost leaks. BOV is sealed shut, wastegate appears to be operating fine. That turbo is capable of flowing some serious air, so a minor boost leak would not keep it from boosting more than 13 psi. I've been working on this thing for many many hours and I am at a loss.

Any advice or suggestions would be greatly appreciated.
Thanks-

 

[matt97gst]

Did you try loosening your BOV adjustment screw some?

 

[Catbox_95]

Did you try loosening your BOV adjustment screw some?

No I haven't. What would that do?

 

[TimG]

Sounds to me like your vacuum line for your BOV has come off or is torn. A Boost leak test will reveal the situation.

 

[Catbox_95]

Sounds to me like your vacuum line for your BOV has come off or is torn. A Boost leak test will reveal the situation.

The line to the BOV is fine, not torn, not leaking. If it were not fine, I would have a leak, and if you notice in my original post, I don't have a boost leak. And plus, with a turbo of that size, I tiny hose would not keep the turbo from spooling up more than 13 psi. But again, I have no boost leaks.

 

[matt97gst]

BOV sounded too tight, but being looser shouldn't help your problem, nevermind. Do you have both nipples in use on your Tial wastegate? I know if you don't you'll have no control of boost with the profec.

 

[Catbox_95]

Yes, the Profec is hooked up properly and I am using both nipples. The car hauled ass a couple days ago, and then all of a sudden it lost the ability to boost. I have done nothing new to the car, which is why it's so baffling.

 

[TimG]

The line to the BOV is fine, not torn, not leaking. If it were not fine, I would have a leak, and if you notice in my original post, I don't have a boost leak. And plus, with a turbo of that size, I tiny hose would not keep the turbo from spooling up more than 13 psi. But again, I have no boost leaks.

My buddies 60-1 popped the little vacuum line off for the BOV this season at the track. Not only was it leaking out of the vacuum line but the BOV wouldn't stay shut. He was able to make about 11psi and the BOV sound was non-existant. That's why I threw that out there. Just very similar and trying to help you pinpoint the part which may have failed. (BOV?)

 

[matt97gst]

My buddies 60-1 popped the little vacuum line off for the BOV this season at the track. Not only was it leaking out of the vacuum line but the BOV wouldn't stay shut. He was able to make about 11psi and the BOV sound was non-existant.

I had a hole in my line from my BOV once. The most obvious side effect was an abnormally high and bouncy idle.

 

[TimG]

I had a hole in my line from my BOV once. The most obvious side effect was an abnormally high and bouncy idle.

A hole vs popping it off isn't the same thing. It still can hold boost and aid the BOV in staying shut.

 

[Catbox_95]

I don't have a hole in my line.

It didn't pop off.

 

[TimG]

I don't have a hole in my line.

It didn't pop off.

Great. Is there any way for you to test the blow off valve itself? I'm really believing it's the issue here. A friend with the same one you can swap or maybe there's a test procedure that can be used with an air compressor that I'm unaware of.

What are you pressure testing the intake tract too in psi?

 

[Catbox_95]

I took it off and did the air compressor test procedure. The BOV still looks and works like brand new. There is no internal leak, and when pressure is applied to the nipple, it holds the valve shut tight.

Is it safe to just block off the BOV flange and make a test run without a BOV?

 

[TimG]

I took it off and did the air compressor test procedure. The BOV still looks and works like brand new. There is no internal leak, and when pressure is applied to the nipple, it holds the valve shut tight.

Is it safe to just block off the BOV flange and make a test run without a BOV?

No but I've done it before. It makes a real cool sound too when you let off the throttle after a WOT run. Like a duck quacking or something.

If you have a two-step/studderbox then you could try to build boost past 13psi at a stand still without having to close the throttle plate abruptly and potentially harming your turbo.

 

[oldman]

No but I've done it before. It makes a real cool sound too when you let off the throttle after a WOT run. Like a duck quacking or something.

Yes, the cool sound of compressor surge, I wouldn't recommend to anyone though.

Catbox_95, seems like you have got everything considered except for the turbo itself. Test run with no vac lines connected to the wastegate. If you still can't get past 13psi, you most likely have a dying turbo. If pressure shot past 13psi, double check your EBC/wastegate hook ups.

 

[Spidey]

Just wanted to add that if your wastegate wasn't opening, boost would continue to rise, so you must be losing it somewhere else.

 

[Catbox_95]

I eliminated the EBC and stuck on an MBC, and it's no different. Wastegate never even gets to the point where there's enough boost built up to open it.

I just found 2 bolts that hold the header to the turbo are loose and I can physically see a gap between the header and the turbo. Perhaps this might be the culprit. It still seems to be losing an aweful lot of boost to just be that exhaust leak, but I'll check it out.

 

[oldman]

I just found 2 bolts that hold the header to the turbo are loose and I can physically see a gap between the header and the turbo. Perhaps this might be the culprit. It still seems to be losing an aweful lot of boost to just be that exhaust leak, but I'll check it out.

If you can see the gap, it will make a big difference and is probably the source of your problem. Fix it and see what happens.

 

[zachdeagle16]

Check the turbo of and check for shaft play, you could be missing fins on the exhaust side.

 

[Catbox_95]

First of all, thanks for everyone's help so far.

I tightened the exhaust housing to the header, no leaks. I bolted a solid plate under the BOV to eliminate the possibility of a bad BOV. Still, low boost problems.

There is no shaft play front to back or side to side. Turbine spins very freely, feels real smooth.

I've been working on this for countless hours now, and the more I work on it and test it, the less I'm able to boost. The problem is getting worse each time I take it out. First it was 17 psi max, then 13 psi max, last night I could only hit 11.5 psi, today I hit 10.5 psi max, and now on my last test, just 9.5 psi max.

The only thing left it could be, in my opinion, is the turbo itself. My friend suggested that there is an O-ring gasket inside the compressor wheel side that is probably bad. The turbo is new and I take good care of it, but recently a shop loosened the bolts to clock the position of the outlet to better meet up with the intercooler piping. I wonder if they damaged the O-ring in the process.

Since I've tried everything else, tonight I will pull the turbo off and take it apart. Any suggestions or help in this area are also appreciated.

 

[oldman]

Without going back and re-read the thread, I have a suggestion before you pull the turbo.

Leave both nipples on the wastegate open, no ebc and mbc so the wastegate will never open. If problem persists, with no exhaust and intake leaks, go ahead and pull the turbo. If you get run away boost, the problem isn't the turbo, most likely a defective wastegate either opening too early by intake pressure or being blown open by exhaust flow.

 

[Catbox_95]

Yeah, I tried that too, and still no boost. Pulling the turbo will be no picnic, and I wish there was an alternative, but I see no other choice right now.

 

[TimG]

I wonder if the shop didn't tighten the bolts down significantly after they clocked the turbo. You'll see when the thing is off the car. But if you are pressurizing the intake system from the turbo inlet, it should leak if theres an issue with the seal.

 

[oldman]

I wonder if the shop didn't tighen the bolts down after they clocked the turbo. You'll see when the thing is off the car. But if you are pressurizing the intake system from the turbo inlet, it should leak if theres an issue with the seal.

The seal is between the back plate and the center section, I'm worrying more about leaking between the back plate and the compressor cover. My to4e cover was leaking a lot of air, brand new turbo, I had to remove it and apply hi-temp RTV. Catbox, did you really pressurize from the intake? How much pressure were you able to pump into the system. Be honest.

 

[Catbox_95]

Found the problem! Sheesh, finally...

Since I know the suspence is killing you all, I'll tell you. But first, I would like to state that I DID perform a boost leak test. If you've been following this entire thread, you know that the body of the car had torn a cut in a coupler that connected intercooler piping. When I took that apart to replace it, I ran the boost leak test.

A-ha! (you say..)

That only tests those parts after the intercooler. And they were all fine.

So tonight I took the turbo off. Then I took the turbo apart. It looks brand new, couldn't BE in better condition. So while it was off and I had the ENTIRE turbo system easily at my disposal, I ran the boost leak test from the TURBO back.

Definitely more thorough.

It was then that I called my wife out in the garage to help me listen for the HUGE leak. Yeah, it was the intercooler. The top of it has separated from the rest of it.

I find myself in the same predicament that I could imagine a parent of a teenager who stayed out 5 hours past curfew. While I'm PISSED that I took the entire turbo system apart and spent 3 days scratching my head with it, I'm glad the hunt is finally over.

Thanks again for all who helped.