Can't find boost leak source

I've been making less power since I switched to the twinscroll version of the vargas stage 2. The process of changing the housing shouldn't cause the problem since Vargas did it when I sent my turbo back for warranty purposes. I did a smoke test at first and the factory diverter valve was smoking so I replaced it with the gofastbits ones. Went to the dyno again and it is still only making 300whp at 22psi. The tuner even tried 29psi since my car is on watermeth, but no power gain at all. The boost reads fine but car is not making power as it should be, tuner said it is the turbo, but Tony from Vargas said it is not. Anyone can chime in to help me? I could use the money for something else instead of going in a loophole :frusty::frusty:

A boost leak would usually mean you cannot sustain a level of boost, if its drastic. I.E. You shoot for 22PSI but can only sustain 14 to 17 then you you have a pretty bad boost leak, but if your hitting your target 22 and holding or even 29 and holding but not making more power then at least that could pinpoint where to look. (but you may be overboosting/overworking your turbo to maintain 22 or 29psi)

If you are leaking pre-turbo at the inlet it would be obvious. Now if you are leaking after the turbo then depending on where the leak is, you can in theory make target boost, but overwork the turbo to do so. However a malfunctioning waste gate could be bleeding off boost, over work the turbo to make your target and still be low on power.

I would investigate the turbo gasket to the engine block, make sure the 4 13mm bolts are torqued down and have not come loose you will bleed boost and power from there, I would also check the waste gate pre-load etc if its still using the internal unit. Also check the shaft play of both the turbine shaft both axis, and the compressor wheel too.

If you can hold 22 PSI or 29PSI I am surprised there is no difference at all in power as 7PSI even if you are in an overboost situation you should see some increase.

Are you able to maintain your set boost? Also do you have any data logs at 22PSI can you log a 3rd gear pull from 2750RPM to 6500RPM and post the log here?

Have you tried doing a real boost leak test with compressed air?

5.0yote said:

A boost leak would usually mean you cannot sustain a level of boost, if its drastic. I.E. You shoot for 22PSI but can only sustain 14 to 17 then you you have a pretty bad boost leak, but if your hitting your target 22 and holding or even 29 and holding but not making more power then at least that could pinpoint where to look. (but you may be overboosting/overworking your turbo to maintain 22 or 29psi)

If you are leaking pre-turbo at the inlet it would be obvious. Now if you are leaking after the turbo then depending on where the leak is, you can in theory make target boost, but overwork the turbo to do so. However a malfunctioning waste gate could be bleeding off boost, over work the turbo to make your target and still be low on power.

I would investigate the turbo gasket to the engine block, make sure the 4 13mm bolts are torqued down and have not come loose you will bleed boost and power from there, I would also check the waste gate pre-load etc if its still using the internal unit. Also check the shaft play of both the turbine shaft both axis, and the compressor wheel too.

If you can hold 22 PSI or 29PSI I am surprised there is no difference at all in power as 7PSI even if you are in an overboost situation you should see some increase.

Are you able to maintain your set boost? Also do you have any data logs at 22PSI can you log a 3rd gear pull from 2750RPM to 6500RPM and post the log here?

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Yes I am able to maintain the set boost. No datalogs from me, I will be leaving next week for a few months vacation so I won't be able to fix the car yet until then.

Marvinmadman said:

Have you tried doing a real boost leak test with compressed air?

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Not yet, I will do once I get back here in a few months after a long vacation lol

OxWhiteEB said:

Not yet, I will do once I get back here in a few months after a long vacation lol

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I hope you figure it out man, that's alot of money for something to not work properly. I don't have anything scientifical to contribute besides pointing out that someone on the forum will have some insight when you get back. best of luck.

OxWhiteEB said:

Yes I am able to maintain the set boost. No datalogs from me, I will be leaving next week for a few months vacation so I won't be able to fix the car yet until then.

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Yeah the main thing here is if your making target boost, and your AFRs are good and you have timing advance you should be making more power, there should be no reason you are not.

Without a datalog its tough. A smoke test will only give you a low PSI check on leaks and that is not sufficient to find an actual high pressure leak. Smaller leaks usually overwork the turbo because the electronic boost controller on your car will attempt to infer requested boost even if you are bleeding off a PSI or two, but that is at the cost of overworking your turbo, small amounts is not a big issue but what you are saying is you are hitting your targeted tuned boost level but not making more power. Is this solely based on a Dynometer without data logs?

Because lets face it at 26PSI on my big turbo I should have been sitting at somewhere around 390WHP and I was hitting 353, but that could have just been the dyno I was on, on a different dyno on a different day I could have been on point or close. If you are saying you ran 29 PSI on meth (I think you still would have been under fueled at 29 PSI) and you still made the same WHP then other than a turbo failure I am not sure any boost leak would produce the exact same number with 7 more PSI regardless, more boost, more octane would have resulted with more timing and it would have been more power.

Very few issues would prevent more power with more boost because unless its bleeding off after the pressure sensor but before it gets to the cylinders which I cannot imagine how that happens, I think our MAP sensor is on block/intake on the right side.

So maybe an intake gasket leak or a crack in the intake, or something leaking on the intake itself where boost is being recorded at the MAP but leaking as fast as it can get into the intake/head but you can maintain boost?? Your turbo should be able to make far more than 29spi (My precision was trying to pump 45PSI at one point till the tune was dialed in)
If you were leaking after the head you would have a hard time making boost, or if the WG failed to close would lose boost and not maintain it fast enough.

Logs would tell us what is going on, see the waste gate duty cycle, STFT, boost pressure, pedal position, etc. All that is needed to guess this in a forum thread, but as previously stated by others you need to do a proper boost leak test.

I'm having similar issues with my car. Mine's a VS2+ and sustains as much as 28psi, but isn't going anywhere fast, at all.

I just replaced the standard wastegate w/the Turbosmart version. Still the same issue.

I'm getting ready to start testing on E85, and know we're already outta fuel on the 93 tune but can't for the life of me believe that the car would be *slower* with the built motor and VS2+ on 93 than when it was on stock turbo and 93.

I haven't been able to do the full leak test where you put a capped coupler to the turbo with a compressor. Hoping to do that this weekend though.

MiDiablo said:

I'm having similar issues with my car. Mine's a VS2+ and sustains as much as 28psi, but isn't going anywhere fast, at all.

I just replaced the standard wastegate w/the Turbosmart version. Still the same issue.

I'm getting ready to start testing on E85, and know we're already outta fuel on the 93 tune but can't for the life of me believe that the car would be *slower* with the built motor and VS2+ on 93 than when it was on stock turbo and 93.

I haven't been able to do the full leak test where you put a capped coupler to the turbo with a compressor. Hoping to do that this weekend though.

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Can you give me updates on your issues? Thanks!

OxWhiteEB said:

Can you give me updates on your issues? Thanks!

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Crazy actually, it wound up being completely unrelated. The transmission (secondhand unit from LKQ) was leaking out of the tailshaft (rear seal), and I hadn't been able to get it fixed. I finally got to replace the tailshaft rear seal and the car came to life!

Not sure if the computer (no codes, btw) was compensating for something knowing that the trans wasn't 100%, or if maybe the fact that the trans was not sealed up tight it was keeping the power from getting through to the wheels.... But whatever, it's night and day difference now (even only on the 93 tune still).

The crowd here is so young.

In another lifetime I had an Evo, the rule was boost leak test every time you touch anything that had to do with the charge system.

If your target boost is 25 psi test it at 30psi.

Next, VERY important, move the charge pipes around. So many times people will do a boost leak test and the car will run like trash on the street. Why? Because the motor moves and opens up new leaks.

The car should also be hot, if not you'll have boost blown by the rings and come out of the pcv and valve cover breather. I always reccomend to cap those before doing a test.

If you're losing pressure fast and can't find it use some dish soap and water in a bottle to spray in different areas, you'll have leaks in places you were sure were fine.

There is a right way and a wrong way to install charge pipes. Always clean the inside of the coupler and the outside of the pipe with brake clean. There should be no residue. Clamps should be installed perfectly straight ok the bead of the pipe, you will have a leak if you don't.

Lastly be careful, wear eye protection. You can easily get your eye hit if something was to pop off.

Before my Shelby I had a 400 whp EB with a FFTEC BT kit on 91 and meth, I had the second kit made by them and did a big review on it. The few times that I had issues with power were due to boost leaks.