Boost leak symptoms, but no boost leak?

[dragrush]

I recently got my car dynoed and found out the boost slowly drops off as rpm's climb as seen on this graph (boost is green line) http://dsmtuners.com/gallery/showimage.php?i=77801&catid=newimage

The shop i took it to as well as I tested for boost leaks up to 30 psi and found none. It holds 30 psi for a few minutes before it drops to 0 and cant here no hissing anywhere. Also no exhaust leaks

The shop said they looked at my Tial 38mm extrenal Wastegate and said it was in working condition as well as the elcetonic blitz BC. They said they think it may be the turbo goinng out on me. ( No shaft play) Is there ways to test the tial wastegates?

Compression is 165 on all 4 and leak down test is less than 10% on cold engine

Also idles around 2000 rpms (another symptom of boost leak)


Still put down decent numbers for pump gas, but I think I can get more if the boost held. Any suggestions/comments/questions? Thanks in advance

 

[Talesin]

Actually, the high idle is a sign of a vacuum leak. A vacuum leak is also a boost leak, but not always vice-versa. Have you tried grounding the correct connector and adjusting the BISS to bring your idle down? And when you were doing the boost leak test, did you have the throttle body plate open?
Your turbo may not be going out on you, but it may be overrunning its efficiency map. Really shouldn't be doing that on a 50-trim though. Could be your intercooler heatsoaking, depending on how they're getting that boost reading. What did your actual boost gauge say during the pulls?

 

[oldman]

The shop i took it to as well as I tested for boost leaks up to 30 psi and found none. It holds 30 psi for a few minutes before it drops to 0 and cant here no hissing anywhere. Also no exhaust leaks

I wouldn't believe that for a second, do your own BLT.

 

[DSMunknown]

^^ He means "I wouldn't".

 

[oldman]

^^ He means "I wouldn't".

Don't know what you talking about.

 

[DSMunknown]

^^ Bruce, get off the intranet! You're staring at the screen too long and making "gramer" mistakes.

 

[dragrush]

I havent tried grounding the connector, to adjusting the biss. Not sure how to do it, but Ill look into it and try it. The biss is all the way down as of now.
I acutally never did a boost leak test with the throttle open, Ill give that a try and see what it will do.

Im not sure how they got the boost reading either on the dyno sheet, but the boost gauge reads the same as the dyno sheet. Dont think the IC is getting heatsoaked though cause it still losses boost even on the first pull. (its a front mount victory performance IC)

Would a boost/vacume leak cause constant high idle even at start up?

 

[dragrush]

I took off the tial wastegate today and it has a blue spring. Im looking at the tial spring rate charts and there is a small blue and a large blue. http://www.tialmedia.com/documents/w3_tial_38_sp.pdf
Im guessing its the large blue spring which has a min of 1 bar (14.5psi) Anyone know the max hold of psi for this spring? Maybe I just need a stronger spring? I want to hold 26psi at wot so I prob should get a spring that can hold up to atleast 30 psi

 

[DSMunknown]

I took off the tial wastegate today and it has a blue spring. Im looking at the tial spring rate charts and there is a small blue and a large blue. http://www.tialmedia.com/documents/w3_tial_38_sp.pdf
Im guessing its the large blue spring which has a min of 1 bar (14.5psi) Anyone know the max hold of psi for this spring? Maybe I just need a stronger spring? I want to hold 26psi at wot so I prob should get a spring that can hold up to atleast 30 psi

Your answer is right in the Tuner FAQ section. Click here.

 

[dragrush]

Those are the min psi the spring can hold, not the max

 

[vc_wannabe]

yes, for best results have the spring set at the min psi you would be running. Also, check your caps. I too also think your turbo may be going, any white smoke?

 

[link16]

Those are the min psi the spring can hold, not the max

How do I put it? Ah yes, a wastegate spring is the minimum boost, a boost controller may bypass that and allow you to run higher boost.

Let me give you an example: I have a Tial 38mm wastegate with a 5lb spring in it, with a boost controller I can run 30lbs of boost on that 5lb spring; however, I can NOT run LOWER than 5lbs of boost.

I hope this clears this up for you.

 

[dragrush]

There is a little white/bluish smoke at start up, but goes away after warmed up.
I know there is a max limit that each spring can hold. The stronger the spring the less minimum boost level you can run, but higher max boost levels. Is the max boost level on a 1 bar spring 18psi? Cause looking at the dyno graph my boost drops from 26psi down to 18. With no boost leaks and a healthy engine its either the wastegate or turbo at fault. Can a big blue tial wastegate spring allow me to boost up to atleast 26psi till redline?

 

[oldman]

Anyone know the max hold of psi for this spring? Maybe I just need a stronger spring?

Approximately 2 x the spring pressure. However, this will vary from car to car, turbo to turbo.

 

[dragrush]

Alright did some more pulls today, and figured out it has to do something with the Greddy profecII boost controller or wastegate.
Once I hit my desired 27psi the external wastegate opens and stays open as the boost falls. I messed around with the boost contoller and the boost always drops no matter what psi I set it too. This is what my settings are set at
Set: 49% (27psi)
Set Gain: 25
Gain: 10%
Warning: 27.5 %
Warning L: 2%

According to the greddy manual if boost drops off at higher rpms turn the gain up. It dosent seem to do much when I turn it up...even at 100% Seems best at around 10%

 

[Talesin]

Sounds like you might be overrunning the efficiency map of your turbo, or may have some kind of exhaust restriction. Short version being, the turbo can't flow enough to provide the full pressure at the top end of the RPM range.

That or your EBC is set up wrong and not letting the wastegate close to maintain the boost level as the flow demand goes up. Which is far more likely. This is why I'd never use one of those POS. MBC, ball and spring, thankyouverymuch, a whole lot less to go wrong, and a whole lot less rice in the cabin. You're riding in a GSX, so you sure as hell don't need to launch at a lower boost level to avoid wheelhop like the FWD guys do.
IMO, sell off the overpriced (and overriced) EBC to a GS-T owner, and buy a ball and spring MBC.

PS- 1bar = 14.7psi, so it's unlikely that 18psi would be your 'max' if the spring is rated at 1bar.

 

[kenamond]

The WG seems to hold 26psi from your dyno graph. I don't see why it would hold and then not hold. Sounds like the EBC to me ... or exhaust restriction to me (though I don't see why it would drop right after boost hits). I agree that you should try to pick up a cheap ball-spring MBC and see if that helps. If it does, keep the MBC and sell the EBC...or double-check how you have the EBC wired and tuned.

 

[dragrush]

The EBC is hooked up correctly. Local Performance shop doubled checked. I also have slowboy racing cast manifold and 3in turbo back exhaust (no cat) So the exhaust really isint restricted. Ill pick up a manual boost controller and see what that does. they dont cost much. Ill let u know if that cures the problem. Thanks for help guys

 

[dragrush]

Got a hallman pro manual boost contoller, put it in and when it hits 27psi it drops to 15 psi now instead of 18. Thought it was a boost contoller problem of my wastgate staying open when I dont want it too. Seems like my wastegate is letting out to much pressure. I just want it to hold at 27. Anyone got any other things I can check or ideas?
And if I did have a boost leak wouldnt my wastegate close once my boost drops?

 

[kenamond]

Another thing you could try is to disable the WGA (you have to be careful with this...). I'm not sure if this is possible with your WG, but it's easy on most internal WGs. If you can disable it (so that nothing is trying to open it - like pulling the BCS vaccuum line off the stock WGA in a stock setup), use the throttle to control your boost CAREFULLY watching your boost gauge, you should be able to hold whatever boost you want. I'd say try to hold it to 21psi or something above where it's dropping to but below what you really want.

This also assumes you have your boost source taken from UPSTREAM of the TB - some folks have their MBC hooked up from the IM (BOV line is one - but not the only - example), but the boost signal the MBC is seeing in this case is from the IM which will be lower than the actual pressure at the compressor outlet due to the large pressure drop across the TB. If you're trying to do what I'm suggesting with a boost source off of the IM, the turbo may be pushing MUCH higher boost than your boost gauge is reading, and you don't want to do that!!

Also, I'd wait a day to see if someone thinks this is a completely stupid idea in your situation.

This would tell you if the spring in the WGA was capable of holding the WG closed under whatever ex. mani. backpressure 21psi (or whatever) boost causes and also at higher rpm.

It might be that the backpressure in the ex. mani. at lower rpm and 27psi boost is much lower than at 27psi boost and higher rpm. In this case, the WG spring might not be stiff enough. I have no gut feel of how the backpressure changes with rpm at fixed boost, though.

 

[dragrush]

I did that once one I had my internal WG to figure out boost problems, but I'm not sure how to do it on a external Tial.
Im guessing once the spring in the wastegate opens (27psi) there is to much pressure to close it agian and thats why it is staying open. Ill try a stronger spring and see what that does. BTW my MBC is connected to the compressor housing and my boost gauge is coming out of the IM. Thanks for help

 

[dragrush]

I put small and large blue spring in the tial WG (23 psi min) I set the hallman pro MBC as low as it can go and the boost spikes to 30+psi and then drops to 20. Really don't know what else to check. Anyone?