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Thread: Turbo overspeeding

              
  1. #26
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    Click here to enlarge Originally Posted by fastgti69 Click here to enlarge
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    ^^ what the hell is that lol Edit, Probably a huge turbo the size of my car huh lol
    http://bimmerboost.com/showthread.ph...-400hp-engines


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    Click here to enlarge Originally Posted by fastgti69 Click here to enlarge
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    ^^ what the hell is that lol Edit, Probably a huge turbo the size of my car huh lol
    http://bimmerboost.com/showthread.ph...-400hp-engines


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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
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    Ahh yes, now I remember!

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    So is this the cause for the turbo siren whine?

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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
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    So is this the cause for the turbo siren whine?
    You've definitely asked this one before hehe. Yes. Overspeed or in rare instances manufacturing defect/bad install.

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    Hello, overspeeding a rotor or compressor, if in fact that is the mode of failure will show up at the root of the blades. So if the tips of a compressor are damaged, chances are that IF overspeed did occur, it didnt directly cause any failure, moreso the tips had dug into the housing due to ROTOR DYNAMICS.

    Rotor dynamics are the frequencies that a longitudinal rotating machine, like any shaft with a rotor that has mass, cause resonances which will force the rotors to bounce around. The fact is, overspeeding as a direct cause of failure is probably not what caused the turbos you see in that picture to fail, because the failures occured at the tip where they probably kissed the housings, which in turn may have been caused by hitting resonance at some excitation frequency (rotor speed) but not the cause of failure due to blade pull (root blade failure).
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
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    Hello, overspeeding a rotor or compressor, if in fact that is the mode of failure will show up at the root of the blades. So if the tips of a compressor are damaged, chances are that IF overspeed did occur, it didnt directly cause any failure, moreso the tips had dug into the housing due to ROTOR DYNAMICS.

    Rotor dynamics are the frequencies that a longitudinal rotating machine, like any shaft with a rotor that has mass, cause resonances which will force the rotors to bounce around. The fact is, overspeeding as a direct cause of failure is probably not what caused the turbos you see in that picture to fail, because the failures occured at the tip where they probably kissed the housings, which in turn may have been caused by hitting resonance at some excitation frequency (rotor speed) but not the cause of failure due to blade pull (root blade failure).
    Well yeah, I thought it was assumed that these turbos didn't get this way just from the centripetal force placed on them. Likely what happened was the thrust wore out (due to overspeed) and the compressors touched the housing. The root cause is still the same thing. The thrust loads when overspeeding are significantly more than the thrust loads the turbo is designed to handle.

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
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    Hello, overspeeding a rotor or compressor, if in fact that is the mode of failure will show up at the root of the blades. So if the tips of a compressor are damaged, chances are that IF overspeed did occur, it didnt directly cause any failure, moreso the tips had dug into the housing due to ROTOR DYNAMICS.

    Rotor dynamics are the frequencies that a longitudinal rotating machine, like any shaft with a rotor that has mass, cause resonances which will force the rotors to bounce around. The fact is, overspeeding as a direct cause of failure is probably not what caused the turbos you see in that picture to fail, because the failures occured at the tip where they probably kissed the housings, which in turn may have been caused by hitting resonance at some excitation frequency (rotor speed) but not the cause of failure due to blade pull (root blade failure).
    Thanks for all your fancy explanations, for the layman he is saying overspeed was not the cause of this failure because the tips are destroyed not the root of the blades. Well thanks for the wordy explanation and yes thats generally how an overspeed condition causes a turbocharger failure during the condition the wheel experiences expansion then collision with the housing which then quickly causes a catastrophic failure, all it takes is one of the extremely fragile blades to break, you can snap one with one finger pushing on it hard enough, to throw it out of balance and the wheel ends up looking like that. Another is overspeed taking out the thrust or journal bearings and again you get a collision with the housing. Honestly not sure what you do, but its quite obvious you like to throw around big words and prove how smart you are. How many catastrophic turbocharger failures have you examined in your life, to join this discussion and speak in fact it must be quite a few? How many turbochargers have you actually taken apart to determine cause of failure from at all? I have seen many a burst wheel from overspeed, I actually had a Porsche 996 turbo brought in yesterday that burst the turbine wheel from overspeed and put a hole through the side of a stainless steel turbine housing where a piece of the wheel came out like a bullet, that was a very easy one to diagnose. This one may or may not have been overspeed, but it is likely. My ENTIRE POINT of this post was to let people know overspeed kills turbochargers, and dealing with such small turbos as this platform does its very easy to achieve an overspeed condition while going for big power. If you want to tell everyone here overspeed didn't kill this one, thats your right, I won't argue with you as the cause of this failure could have been a number of things. Thanks for the display of intelligence.
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  9. #34
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    ^ Thanks for that. Basically what I was thinking.

    I am still baffled by how many people just can't believe that pushing 18+psi through these snails could cause these issues... Click here to enlarge Like these turbos are supposed to withstand that kind of abuse or something... More boost, especially that off the chart, is going to wear the turbos faster. How much depends on tuning, the specific hardware, and the adjustment/maintainence of that hardware.
    Last edited by rudypoochris; 12-01-2012 at 02:32 AM.

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    Click here to enlarge Originally Posted by VargasTurboTech Click here to enlarge
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    Thanks for all your fancy explanations, for the layman he is saying overspeed was not the cause of this failure because the tips are destroyed not the root of the blades. Well thanks for the wordy explanation and yes thats generally how an overspeed condition causes a turbocharger failure during the condition the wheel experiences expansion then collision with the housing which then quickly causes a catastrophic failure, all it takes is one of the extremely fragile blades to break, you can snap one with one finger pushing on it hard enough, to throw it out of balance and the wheel ends up looking like that. Another is overspeed taking out the thrust or journal bearings and again you get a collision with the housing. Honestly not sure what you do, but its quite obvious you like to throw around big words and prove how smart you are. How many catastrophic turbocharger failures have you examined in your life, to join this discussion and speak in fact it must be quite a few? How many turbochargers have you actually taken apart to determine cause of failure from at all? I have seen many a burst wheel from overspeed, I actually had a Porsche 996 turbo brought in yesterday that burst the turbine wheel from overspeed and put a hole through the side of a stainless steel turbine housing where a piece of the wheel came out like a bullet, that was a very easy one to diagnose. This one may or may not have been overspeed, but it is likely. My ENTIRE POINT of this post was to let people know overspeed kills turbochargers, and dealing with such small turbos as this platform does its very easy to achieve an overspeed condition while going for big power. If you want to tell everyone here overspeed didn't kill this one, thats your right, I won't argue with you as the cause of this failure could have been a number of things. Thanks for the display of intelligence.
    Hes an engineer. Be nice, he knows his $#@!. I dont think he was trying to argue against you.

    Last thing I think he was working on was designing turbine blades for a 5000hp jet engine....there are pics around here somewhere

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    Click here to enlarge Originally Posted by Itsbrokeagain Click here to enlarge
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    Hes an engineer. Be nice, he knows his $#@!. I dont think he was trying to argue against you.

    Last thing I think he was working on was designing turbine blades for a 5000hp jet engine....there are pics around here somewhere
    Like a typical Engineer (and I am one too btw), he was basically arguing semantics.

    YES it is most likely these turbos didn't fail by throwing a blade (except maybe the catastrophic failure). The root cause of these failures is still due to overspeed since overspeed often causes thrust failure and expansion of the metal on the wheel to the point that it contacts the housing.

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    Click here to enlarge Originally Posted by Itsbrokeagain Click here to enlarge
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    Hes an engineer. Be nice, he knows his $#@!. I dont think he was trying to argue against you.

    Last thing I think he was working on was designing turbine blades for a 5000hp jet engine....there are pics around here somewhere
    I don't think he was either to be honest, just kinda seemed like he likes to let everyone know how smart he is was my only point. Just because you work on one thing technical doesn't make you an expert on another. He is prob a super cool guy, you can never tell on these forums. Its like arguing with your GF over text, everything gets lost in translation and you never really solve anything til you see them in person.
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    Great info from both sides. Love this forum.

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    Another great informative article. It seems to me that it is inevitable that the turbos wear down faster with a tune, and there is not much one can do to remedy it. What should one be wary about when going with an ECU flash like the Cobb to prevent turbo wear? I'm guessing that overspeeding of the turbos will occur less frequently with better cooling?

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    Click here to enlarge Originally Posted by Karura Click here to enlarge
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    Another great informative article. It seems to me that it is inevitable that the turbos wear down faster with a tune, and there is not much one can do to remedy it. What should one be wary about when going with an ECU flash like the Cobb to prevent turbo wear? I'm guessing that overspeeding of the turbos will occur less frequently with better cooling?
    If you're boosting super high why would cooling change the overspinning? Cooling or no cooling they still need to spin a certain RPM.

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    You're right, that makes sense; for some reason I was thinking about intercoolers/denser air and got it confused with turbos. Now that I think about it, intercoolers are after the turbos, so why cooling ever came across my mind... Click here to enlarge

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    So how much boost is too much boost? If I remember correct the stock tubo efficiency can go up to like 20-22 psi? Granted it shouldn't be done but the stock turbos are capable of this no?

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    Click here to enlarge Originally Posted by 3-Serious Click here to enlarge
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    So how much boost is too much boost? If I remember correct the stock tubo efficiency can go up to like 20-22 psi? Granted it shouldn't be done but the stock turbos are capable of this no?
    Depends on your RPM. 20psi at 3000 is wayy different than 20psi at 6000

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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
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    Depends on your RPM. 20psi at 3000 is wayy different than 20psi at 6000
    And that's where the compressor maps come into play..

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    Click here to enlarge Originally Posted by Karura Click here to enlarge
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    Another great informative article. It seems to me that it is inevitable that the turbos wear down faster with a tune, and there is not much one can do to remedy it. What should one be wary about when going with an ECU flash like the Cobb to prevent turbo wear? I'm guessing that overspeeding of the turbos will occur less frequently with better cooling?
    Turbo speed goes up with more boost, better intercooler, and the use of meth. Basically anything that reduces pressure drop, increases boost, or increase charge density after the turbo will result in more turbo speed since the turbo now has to fulfill more air mass. So better intercooler is harder on the turbos.

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    Click here to enlarge Originally Posted by 3-Serious Click here to enlarge
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    So how much boost is too much boost? If I remember correct the stock tubo efficiency can go up to like 20-22 psi? Granted it shouldn't be done but the stock turbos are capable of this no?
    You can be on the map with 22lbs at 3800rpm, but you will be off map unless you drop boost down very quickly as revs rise. You shouldn't doing more than 14 or so at 6500rpm if you want the things to last imho.

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    Does it make sense that turbos spin less with cooler temps to hit the same level of boost, due to the denser air mass? Hitting 22psi in 90F ambient would require a higher WGDC (making them spin faster) compared to when it is 32F outside right? Just thinking out loud here...
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    Click here to enlarge Originally Posted by VargasTurboTech Click here to enlarge
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    Thanks for all your fancy explanations, for the layman he is saying overspeed was not the cause of this failure because the tips are destroyed not the root of the blades. Well thanks for the wordy explanation and yes thats generally how an overspeed condition causes a turbocharger failure during the condition the wheel experiences expansion then collision with the housing which then quickly causes a catastrophic failure, all it takes is one of the extremely fragile blades to break, you can snap one with one finger pushing on it hard enough, to throw it out of balance and the wheel ends up looking like that. Another is overspeed taking out the thrust or journal bearings and again you get a collision with the housing. Honestly not sure what you do, but its quite obvious you like to throw around big words and prove how smart you are. How many catastrophic turbocharger failures have you examined in your life, to join this discussion and speak in fact it must be quite a few? How many turbochargers have you actually taken apart to determine cause of failure from at all? I have seen many a burst wheel from overspeed, I actually had a Porsche 996 turbo brought in yesterday that burst the turbine wheel from overspeed and put a hole through the side of a stainless steel turbine housing where a piece of the wheel came out like a bullet, that was a very easy one to diagnose. This one may or may not have been overspeed, but it is likely. My ENTIRE POINT of this post was to let people know overspeed kills turbochargers, and dealing with such small turbos as this platform does its very easy to achieve an overspeed condition while going for big power. If you want to tell everyone here overspeed didn't kill this one, thats your right, I won't argue with you as the cause of this failure could have been a number of things. Thanks for the display of intelligence.
    why are you so sensitive dude? I wasnt arguing with you, just explaining the root cause of failure. Enough with the chest pounding...

    BTW forgot to add, the only real way to know if the failure in the pictures was caused by overspeed is to have a log somewhere showing turbine RPM or boost or something... Because these little turbos do spin up in the 200k RPM range and there are lots of people doing it. Just saying, it could be FOD or something, nothing is certain if you don't have data.
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    Click here to enlarge Originally Posted by nitehawk Click here to enlarge
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    Does it make sense that turbos spin less with cooler temps to hit the same level of boost, due to the denser air mass? Hitting 22psi in 90F ambient would require a higher WGDC (making them spin faster) compared to when it is 32F outside right? Just thinking out loud here...
    Yes that is exactly right. If you look at the compressor map, the x axis is corrected flow which is non-dimensional mass flow (takes out ambient temperature from the equation).

    So playing with inlet temps is huge for compressor efficiency and mass flow.

    Think of it like this, lets say you built a compressor shaped exactly like the stock N54, and you could theoretically spin it to 300k RPM without it exploding, would it flow more? The answer is no, there is a limit to the mass flow, and it is geometrically constrained because of the compressor and scroll, eventually, you just cannot move more air no matter how fast you spin it.

    So keeping rotor speed down is always always a plus, and that can be done by various means, pre turbo meth and lowering ambient temps being one way...
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    Click here to enlarge Originally Posted by rudypoochris Click here to enlarge
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    Well yeah, I thought it was assumed that these turbos didn't get this way just from the centripetal force placed on them. Likely what happened was the thrust wore out (due to overspeed) and the compressors touched the housing. The root cause is still the same thing. The thrust loads when overspeeding are significantly more than the thrust loads the turbo is designed to handle.
    Blades touching housings can occur even when there is no overspeed, due to imbalance, FOD, oil starvation etc... So it is hard to say what exactly caused that, it may be overspeed or it may not.

    You cant say with all certainty that if the blades touched the housings that it was overspeed, many things can cause that. If you have data logs of the failure event, maybe we can know more about this failure.
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