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Old 07-08-2012, 03:53 PM   #1
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Default Is compressor surge what just killed my turbo?

Trackday at Sebring, woohoo! Around 8 laps in during the first session, and under acceleration, I heard a mechanical pop under the hood and the boost went from 10psi to zero instantly. Then after the next corner it started to work a little and quickly stopped again. I thought I might have blown a silicone hose partially off or something so I limped it into the pits. After I got there I left the car running and opened the hood to inspect everything. After pulling the air filter (hot hot aww crap that's hot) I saw the compressor spinning and wobbling. The whole shaft of my EMUSA Chinese 2870 was wobbling. I touched the throttle by hand and the turbo seized and released while the engine was lightly revved. That bastard! It was only the first session of the day!

So now, the post-mortem begins.

After studying a bit, I've come to the determination that the really neat fluttering sound I was used to hearing when I shifted or especially when I short shifted from full throttle was not a good sound. I was supposed to hear a strong PSSSHHH from the Bosch blowoff valve instead. The Bosch does open and is not stuck but must open far too slowly or with much too small an orifice for my turbo's needs.
To quote the Garrett site:
Quote:

What is compressor surge?
The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side.
Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself.
Common conditions that result in compressor surge on turbocharger gasoline engines are:

* A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
* The outlet plumbing for the bypass valve is too small or restrictive
* The turbo is too big for the application
Durr! I am probably guilty of the last two of those three criteria. The last one is hard to tell because there are no Chinese compressor maps.

So I know I need another turbo. Do I need a bigger BOV or just one that works more quickly? Can I go with the same size turbo or was that really part of the problem?

You can hear it often when I shift, especially in corners like the one at 1:15 (ignore the noisy 3 rotor RX8)


And even easier to hear at 1:04 and the next few corners afterward in this video:


What do you guys think? Did surge flutter kill my turbo? I need to know before replacing it.

When I get it off the car I will double check oil flow and try to disassemble the turbo to check for starvation or other possible issues. Oil pressure gauge has warning lights and audible alarm so I know pressure was good (was seeing stable 34psi when very hot and on the track).
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Old 07-08-2012, 04:08 PM   #2
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I believe the "surge" or flutter noise from the BOV when not under-load is harmless. Your blow off sounds like mine.

You have a China turbo, get real.
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Old 07-08-2012, 04:13 PM   #3
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I believe the "surge" or flutter noise from the BOV when not under-load is harmless. Your blow off sounds like mine.

You have a China turbo, get real.
But the sound was coming from the compressor inlet and not the BOV. They are on opposite sides of the car so it was easy to tell.
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Old 07-08-2012, 06:51 PM   #4
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Was the bov not operating then?
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Old 07-08-2012, 07:50 PM   #5
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I could tell it was opening at idle but I don't think it was pulling open quickly enough to do what it needed to be doing to stop the backpressure through the compressor.
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Old 07-08-2012, 10:02 PM   #6
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That didn't really sound like surge to me, but I've only heard it in real life on a k03. On one of those is sounds kind of like a helicopter. One issue could be that your bov is adjusted for too high of a boost pressure. I prefer the inline style blowoff valves like this one since they dont have to be spring biased against boost pressure to prevent leaking. OBX also makes a cheaper version of the one I linked for like 80 bucks.
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Old 07-08-2012, 10:20 PM   #7
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Quote:
Originally Posted by Leafy View Post
That didn't really sound like surge to me, but I've only heard it in real life on a k03. On one of those is sounds kind of like a helicopter. One issue could be that your bov is adjusted for too high of a boost pressure. I prefer the inline style blowoff valves like this one since they dont have to be spring biased against boost pressure to prevent leaking. OBX also makes a cheaper version of the one I linked for like 80 bucks.
You prefer that over a TiAL Q? What makes it so much better?

He's right though, if the spring is too stiff then it could not vent. Mine makes a chirpy-sound at low boost pressure but the noise comes out the valve and not the turbo.
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Old 07-08-2012, 10:28 PM   #8
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It doesnt need to be biased against the input pressure. Its literally put in the intake piping, as it comes out of the box, connect to vac, and start the car. Rather than doing all that, and futzing around with the springs so it doesnt leak under full boost, but will actually open too. Which also means it opens the same and with the same speed if you have 2psi in the intake tubing or 30psi.
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Old 07-08-2012, 11:28 PM   #9
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Quote:
Originally Posted by Leafy View Post
It doesnt need to be biased against the input pressure. Its literally put in the intake piping, as it comes out of the box, connect to vac, and start the car. Rather than doing all that, and futzing around with the springs so it doesnt leak under full boost, but will actually open too. Which also means it opens the same and with the same speed if you have 2psi in the intake tubing or 30psi.
Spring selection is determined by closed-throttle vacuum pressure. Mine opens find and holds to 18psi and beyond. That one in the link is the same price as the TiAL and I fail to see why it's better.
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Old 07-08-2012, 11:35 PM   #10
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Well I also think they look cleaner and are otherwise easier to install. Since all you need is a gap in a straight section of pipe rather than a flange. Either way I haven't looked at bov's much at all since deciding on going EFR. And I only point this one out because I've seen it before and personally I think the system is much more... sophisticated, than a normal bov.
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Old 07-08-2012, 11:46 PM   #11
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Quote:
Originally Posted by Leafy View Post
Well I also think they look cleaner and are otherwise easier to install. Since all you need is a gap in a straight section of pipe rather than a flange. Either way I haven't looked at bov's much at all since deciding on going EFR. And I only point this one out because I've seen it before and personally I think the system is much more... sophisticated, than a normal bov.
My number one concern is functionality, #2 is service interval. The TiAL stuff is rigorously tested like this wastegate:

I think that is worthy of consideration.
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Old 07-09-2012, 12:09 AM   #12
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I had no idea they made inline BOVs, cool.

My ebay RFLBOV is awesomely loud, however it leaks at idle and snaps shut with any throttle input. The sudden absence of that air causes it to be stutter off idle, but I can deal with it on something that's not a DD.

Certainly makes you realize the importance of the correct spring.
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Old 07-09-2012, 02:37 PM   #13
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Old 07-09-2012, 02:47 PM   #14
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I dont hear compressor surge. But your BOV is too tight and could be causing some backwards pulses through the compressor as it's fluttering.


the person who made the above video is retarded. the noise is the bov opening and closing rapidly because they didn't tune the spring pressure properly (ie. too tight). if the turbo was making the noise out the intake it would sound a little differently.

ah i see it's synapse...they like to stretch the truth a little to sell product.


if i was by my car i could demonstrate this by blocking the bov outlet and revving the engine.
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Old 07-09-2012, 08:23 PM   #15
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So something else likely killed my turbo? Like it being Chinese or something? Everybody's got a great, reliable Chinese turbo but me. Great.

I am curious to see if it was getting proper oil volume. That and FOD are all I can think of that would cause a failure and there is no evidence of FOD.
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Old 07-09-2012, 08:31 PM   #16
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there's been one or two other guys out there that had them fail, or perform shitty as hell.

didn't someone get one bad from the get-go? even those begi shanghai ones have had issues.
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Old 07-09-2012, 09:29 PM   #17
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I might inspect it and buy a $40 rebuild kit from the same Chinaman that sold me the terboo if everything looks usable. It's just $40 bucks and I'm one hell of a cheapskate, hence Miata. Is the second time a charm?
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Old 07-09-2012, 10:19 PM   #18
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Quote:
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Marketting, and Chinese plastic crap as well.
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