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Boost leak in turbo? Any suggestions?

Boost leak in turbo? Any suggestions?

Boost leak in turbo? Any suggestions?

(OP)
Hi all~...

I drive a 2003 Tiburon 2.7, turboed with a Garrett GT30R turbo, with a 38mm TiAL wastegate.

The turbo was installed a little over a year ago, putting out 310 WHP at 0.75 BAR of boost (about 10~11 psi) on premium gas.  The wastegate has a 0.6 bar spring, which I raise using a manual boost controller. At this setting, full boost was reached at around 3600 RPM.

A few months ago, boost started going up slower, and not reaching full boost until over 5000 RPM.

It's a big job to take everything out, because of the cramped engine bay, so I just drove the car easy for a few months, until last week, when I had to replace my clutch.

I decided to get to the bottom of the problem while I was replacing my clutch.

I found some exhaust leaks, which I thought was the root of the problem, fixed them, and assumed the car would be okay.

Well, it's not. Right now, at 4000 RPM, the car is only reaching around 0.3 BAR of boost, which is about 4~5 PSI, and to even get to 0.5 BAR, I have to go above 5000 RPM.

I thought that the boost controller may be the problem, taking it out, so that I could get 0.6 bar of boost from the wastegate, but this is not the issue.

I'm at a loss as to where to look for possible boost, vacuum, and/or exhaust leaks.

Can anyone give me some pointers on what may be the issue?

I'm thinking the turbine may be blown, but when I spin it by hand, it spins freely, with no noticeable shaft play, and there's no smoke coming out of my exhaust.

RE: Boost leak in turbo? Any suggestions?

Have you measured the exhaust backpressure?

Mike Halloran
Pembroke Pines, FL, USA

RE: Boost leak in turbo? Any suggestions?

The best way to check for boost leaks is to make some sort of air fitting adapter that you can use to couple the inlet of your turbo to an air compressor.  Then pressurize the entire system with at least as much boost as you plan to run and listen for leaks.

Ralf

RE: Boost leak in turbo? Any suggestions?

(OP)
Thanks for the tips.

Ralf, to measure boost leaks using an air compressor, I assume you mean to hook up the air compressor while the car is turned off, so that the sound of a leak can be heard?

RE: Boost leak in turbo? Any suggestions?

You need to make sure all the inlet valves are closed when you do this. Not so easy if this is an OHC engine.

Check the blow of valve first. It is a likely source of inlet leak

Regards

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RE: Boost leak in turbo? Any suggestions?

yes engine off.

Pat, it's true you may get air leaking into a cylinder (you should remove the oil cap or somthing to make sure pressure dosen't build in the crankcase).  I'm not sure I see the problem with this, maybe you can elaborate?  usually it's quite easy to find all the leaks this way.

RE: Boost leak in turbo? Any suggestions?

If an inlet valve and an exhaust valve are both opened on the same cylinder, like at TDC overlap, the boost will leak straight out the exhaust and the test will not hold pressure.

It needs to hold pressure to test if it only starts to leak before the desired boost pressure

Regards

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RE: Boost leak in turbo? Any suggestions?

Mechaniac:
Sorry to disagree with your comment about stock cams having no overlap, but every OEM camshaft I have worked with in my career has some overlap.

Camshafts with little overlap tend to have better idle characteristics and lower end torque and is the reason many engines today have variable valve timing, to change the overlap at higher engine revs, and on a Hybrid vehicle, the overlap is increased during engine phase-in to assist in starting (Toyota in particular).

To further qualify, an engine with a single camshaft will have overlap while a dual overhead camshaft engine may have varying amounts of overlap.

Franz

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RE: Boost leak in turbo? Any suggestions?

Quote:

Most stock cams don't have overlap

Garbage.

Stock cams have only a few degrees of overlap, especially on 4 valve engines designed for fuel efficiency, but anything made in the last 80 years has some overlap.

Regards

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RE: Boost leak in turbo? Any suggestions?

I thought the new Variable valve systems everyone was making have no valve overlap until the VVT kicks in and then they have a lot more than an old time big block making big HP.

RE: Boost leak in turbo? Any suggestions?

I'm sorry, I still don't see the problem here.
This whole discussion about whether or not engines have very little overlap vs. some overlap is absolutely moot because as far as the OP is concerned, it should be extremely easy to find a crank position where both intake and exhaust valves are not open at the same time (ie. as long as no piston is within about 10-20degrees of TDC then you're fine) and even then, I really doubt the whole overlap thing is an issue to begin with.  If a boost leak is indeed the root of the problem, it has to be big enough such that a GT30R struggles to make 5psi on a 2.7L engine!  In which case, it must be a MASSIVE leak.  I guarantee it will become quite obvious the instant the air is turned on regardless of whether or not any air is leaking out the exhaust!
Sorry for the rant, I just can't believe how overly complicated some people are making this simple problem.

Boggyman, good luck with finding your problem.

RE: Boost leak in turbo? Any suggestions?

(OP)
Thanks for the suggestions, everyone.

Ralf24, if it is not a boost leak, what do you think the issue could be? Could you list a few ideas so that I can get an idea of where to look?

Is it possible that the turbo itself is starting to go bad? It's been about 12 months since I have been running it, so it's should still be going strong. As I said in my first post, there's no noticeable shaft play, the impeller spins fine by hand, and there is not a lot of smoke coming out of the exhaust.

When I disassembled the kit, I took out the wastegate, and pressed on the cylinder, and the spring seemed fine.

Any suggestions, anyone?

RE: Boost leak in turbo? Any suggestions?

You don't seem to have eliminated the possibility of a clogged muffler or cat.



Mike Halloran
Pembroke Pines, FL, USA

RE: Boost leak in turbo? Any suggestions?

Ralf

You are correct.

If you want a down and dirty really simple first check, no need for an adaptor, just wrap the air line with enough rag to jam it into the turbo air inlet with a reasonable seal and block the exhaust outlet with a piston at TDC overlap. The air will leak out somewhere. Also remove oil filler as there might be leaks around worn rings and worn valve guides.

However these problems are often not that simple, and with a large boost leak, often the engine wont even idle properly and blows black smoke out the exhaust as you try to accelerate. Something to do with a:f ratio going out the window as metered air escapes but the fuel for it is still injected. The OP did not mention these very obvious symptoms.

The one air leak that does not do this is an OEM blow off valve as the air is fed back downstream of the airflow or air mass measuring device. An air leak across the chamber and out the exhaust will make it difficult or impossible to measure the blow off valve effective opening point.

Having said all this, I think it most likely is the wastegate valve or spring that is damaged or worn or the muffler has a loose baffle that has moved and partially blocked the exhaust pipe.

Regards

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RE: Boost leak in turbo? Any suggestions?

"it should be extremely easy to find a crank position where both intake and exhaust valves are not open at the same time"   sorry but if it has more than one cylinder it will be extremely difficult to find a crank position with no valves open.

RE: Boost leak in turbo? Any suggestions?

(OP)
Sorry to keep asking questions... :)

Regarding wastegate damage, how does one check if the wastegate valve or spring is damaged? For the spring, I did check it by pressing on the cylinder, and it seemed to be fine. Is there a more concrete way to do this?

Regarding exhaust, I have a 3 inch exhaust, with a huge resonator. The exhaust is only about a year old, which is one of the reasons I eliminated it as a potential problem. However, now that you mention it, my exhaust has become noticeably louder recently.

RE: Boost leak in turbo? Any suggestions?

I just Looked up Tiburon.

It is a V6 24 valve quad cam with no V-tech.

It will most certainly have some overlap.

There will be plenty of stationary positions where the valves will be in an overlap position.

The turbo can be damaged but still spin freely and burn no oil. That damage might be in the form of burnt, bent or broken vanes on either side.

One problem with simple easy tests is they only find easy to find problems. One would hope that anyone posting here had already done the simple tests, and were here to seek advice beyond the obvious.

Regards

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RE: Boost leak in turbo? Any suggestions?

Very often the exhaust actually gets a lot quieter if a baffle moves to block a pipe or passage.

Waste gate test.

make sure there are no leaks upstream.

Make sure the blow of valve cant open and leak, probably by removing it and plugging the holes that leaves.

make sure one piston is at TDC overlap.

Block the exhaust outlet.

Blow air into the airduct at controlled pressure. Note the pressure when you start to hear airflow through the wastegate.

Regards

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RE: Boost leak in turbo? Any suggestions?

Quote:
"Stock cams have only a few degrees of overlap, especially on 4 valve engines designed for fuel efficiency, but anything made in the last 80 years has some overlap."

With a mechanical valve train maybe, but by the time you get this test set up and start checking most all hydraulic vavle trains will have bled off those "few" degrees of overlap.  It's not "garbage" just real world experience.  I guess I didn't specify as well as I should.

Vernon   

RE: Boost leak in turbo? Any suggestions?

The OP does not specify mechanical or hydraulic cam. Neither does the engine specifications I could easily find.

I never said the valves would be open, I said ensure they are not. I stick by that comment.

On another note, I read your post in the link you provided above. If you google search this site on burn rate, octane rating, flame propagation, flame travel etc, you might find what you find illuminating.

Regards

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RE: Boost leak in turbo? Any suggestions?

We do it on small aircraft all the time. A shop vac builds up plenty of pressure to find leaks with a plant mister filled with a soapy solution. Works on the intake as well as the exaust. I dont think these aircraft run as high boost pressures as cars...typical example Cessna 421C runs 39" hg MAP at talkoff, thats about 9" over ambient. What's that 4.5 psig, .3 bar? .

RE: Boost leak in turbo? Any suggestions?

Boogyman, as previously mentioned by others, the three most likely causes would be a boost leak, a faulty wastegate and a partially blocked exhaust.  A boost leak IMO is the most likely and probably cause with the faulty wastegate a close second.  Even if a boost leak isn’t the cause of this problem, I would definitely start there.  A pressure test is not just a simple easy test only capable of finding easy problems.  As Vernon mentioned in his link, this test is an extremely valuable procedure to ensure you’re getting the most out of your setup, and if you’re using a MAF will enable you to maintain a reliable tune.  If you do decide to make an adapter for a full pressure test, please ensure that it’s well made with a nice bead to prevent it from slipping out of the hose coupler.  At 4” diameter, it doesn’t take much pressure to add up to a couple hundred pounds of force trying to pop that thing off.  I don’t know if you’ve put it back on, but I would keep the manually boost controller off the car for now, until you find the problem.  It’s just one more variable you won’t need to worry about, and the bleed hole in it will be a source of boost leak (nothing you can do about that one)

Checking the external wastegate while it’s removed from the car is definitely the way to go.  Make sure it’s not stuck open, and that the spring closes the valve against the valve seat securely.  (I’m guessing that’s what you did from your previous post?).  You can also pressurize the bottom port to ensure that the valve opens and closes smoothly at or around .6 bar.  If all these things check out, then it’s probably not the wastegate.

FoMoCoMoFo, I was referring to intake and exhaust valves within the same cylinder.

Best of luck

RE: Boost leak in turbo? Any suggestions?

Another wastegate check... (simple & obvious kind - sorry if too much so)
With the engine static & cold, check visually and/or by feel that the wastegate valve is fully closed & seated.  If this seems OK, next, locate the hose going to the wastegate canister.  Rig up an air pressure source with a pressure gauge so you can pressurize the canister and see the pressure.  Begin pressurizing, and note the pressure at which the actuator begins to move.  This should be very close to the 0.6 bar you quoted in the OP.  If not, there's your problem.

RE: Boost leak in turbo? Any suggestions?

WELL, JUST A LITTLE INPUT, WHEN I NEED TO PRESSURE TEST A COOLANT SYSTEM, EXHAUST SYSTEM, OR INTAKE, A SIMPLE ADAPTER CAN BE MADE FROM AN APROPRIATELY SIZED INNER-TUBE. WORKS PRETTY GOOD ON RADIATORS. IT HAS A BUILT IN SCHRADER VALVE, SO YOU CAN USE AN AIR CHUCK AND AN AIR PRESSURE GUAGE. JUST CUT THE TUBE, AND CLAMP IT ON. ONLY THING, WITH THIS BIG OF A BOOST LEAK(OBVIOUSLY) YOU MIGHT NEED TO REMOVE THE VALVE CORE TO GET THE AIR IN QUICK ENOUGH. BTW, UNLESS A WELD BROKE ON A CHARGE PIPE, I'D CHECK THE INTERCOOLER, OTHER THAN THAT, THE TURBO ITSELF. THERES A LOT OF AIR FLYING THROUGH THAT ENGINE @ 5 GRAND, SO THE LEAK HAS TO BE HUGE.


A GREAT MAN ONCE SAID: "CHEAP, FAST, RELIABLE, PICK TWO."

-A. D. IADANZA

RE: Boost leak in turbo? Any suggestions?

boogeyman

is it possible you have damaged the turbine?

If this problem showed up gradually over time, perhaps you have gradually rounded over your turbine blades.

RE: Boost leak in turbo? Any suggestions?

Have you checked the induction side before the turbo?

dirty air filter etc, ive seen a plastic shopping bag restrict intake systems more than once!

www.retallickeng.com.au

Was told it couldnt be done, so
i went and did it!

RE: Boost leak in turbo? Any suggestions?

Boogeyman,

Did you ever diagnose the problem?

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