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  1. #1
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    Turbo overspeeding

    Hey guys one of my vendors sends out a newsletter and this month they had a short but informative article on overspeeding. I think it really pertains to this platform with the size of the turbos and the power levels we are running. A lot of turbo problems can be pinned on build error or parts failure when they are in fact caused by overspeed at the root of their problem. We are taking every step to ensure long life for our turbos such as the upgraded thrust option as thrust wear along with over speed is prob where 90% of turbo failures lie. Bottomline, when tuning always err on the side of conservation on boost levels if possible, and if you are running your turbos upgraded or not on the ragged edge. Do not expect to get the full lifespan out of them. Its like driving a tire well past its rated MPH rating everyday and wondering why you are sitting on the side of the road with a blow out. Everyone have a good weekend.

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    It only takes a single significant overspeed event to initiate micro-fatigue cracking on rotor assemblies. Although extremely rare to find a catestophic failure of a turbo on this platform, the most common I've seen in threads is thermal degredation of the compressor wheel causing erosion of the compressor blades. Of course, everyone just upgrades at that point anyway.

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    Great article. This is why its imperative that every turbo manufacturer, hybrid or non-hybrid, provides specs on what their turbos can support safely at least in terms of boost levels and provide compressor maps so shaft speeds, surge lines, etc. are well known and can be tuned for. Otherwise, it ends up as guess work which is never good
    Click here to enlarge

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    It only takes a single significant overspeed event to initiate micro-fatigue cracking on rotor assemblies. Although extremely rare to find a catestophic failure of a turbo on this platform, the most common I've seen in threads is thermal degredation of the compressor wheel causing erosion of the compressor blades. Of course, everyone just upgrades at that point anyway.
    Not so, I have seen more than one catastrophic failure of the stock turbos during tear down, and overspeed holds true for upgrades once you get rid of the stock turbos as well. I think a lot of thinking is, you want more power turn up the boost, this is certainly true in theory but once you reach a certain threshold you are doing more harm than good. The good thing about this platform is I think there has been enough testing to deem what safe boost levels seem to be thus far.

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    Really? Can you post any pics of an contained/uncontained failure? Just curious since I havnt seen any. Completely concur with the boost theory, it's a pretty well understood parameter by most.

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    Have you seen any of this on the N54 cores you recieved?

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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    Have you seen any of this on the N54 cores you recieved?
    None of my cores were bad, I specified I wanted good cores only, but a customer brought his car in for turbos and this was one of his compressor wheels. He was running too much boost and I am suspecting overspeed as the cause. I found the turbine wheel broken at the neck and all the at the entry to the muffler at the back of the car. Literally aluminum chips were everywhere in every pipe, charge and intake, the recirc system just scattered them everywhere. I had to pull everything and have it sent out to be professionally cleaned. If you have a failure like this do yourself a failure and pull EVERYTHING or your new turbos are junk the second you fire it up.
    Last edited by Tony@VargasTurboTech; 11-30-2012 at 12:48 PM.

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    Dzenno,

    There will be guess work no matter what. The maps are great but are really based upon the wheels performance in native housings and without other limiters (ie. N54 OEM restrictive compressor inlet tubing). That said even when provided you must take with a grain of salt in these hybrid applications, and learn the hard way by pushing to find the safe thresholds.

    Fortunately I do not think overspeeding is much of a failure point on this platform, which is shocking since everyone beats the snot out of these things day in and day out. The biggest issues seem to be occasional foreign object damage of the compressor wheel and debris getting into the oil feed. Outside influences from degraded gaskets (ie. valve cover/PCV) seem to be also a big issue on this platform with time/age. We will see more and more of that going forward in time I am certain of that. A tightly sealed induction system is also very important to help compressor efficiency/speeds, and wastegate actuator adjustment (and consistency across banks) is also very important.

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    Speed sensor on each turbo would be awesome info... Knowing first the speeds and also the speed differences that are possible between turbos.

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    Pretty much ALL the BMW Siemens ECU have ALREADY integrated the surging & choke limit model (including the compressor/turbine model) in the source code! Overspeeding a turbo like using a piggyback will cause failure!

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    Wow you werent kidding. Did the engine ingest chips?

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    Click here to enlarge Originally Posted by Rob@RBTurbo Click here to enlarge
    Dzenno,

    There will be guess work no matter what. The maps are great but are really based upon the wheels performance in native housings and without other limiters (ie. N54 OEM restrictive compressor inlet tubing). That said even when provided you must take with a grain of salt in these hybrid applications, and learn the hard way by pushing to find the safe thresholds.

    Fortunately I do not think overspeeding is much of a failure point on this platform, which is shocking since everyone beats the snot out of these things day in and day out. The biggest issues seem to be occasional foreign object damage of the compressor wheel and debris getting into the oil feed. Outside influences from degraded gaskets (ie. valve cover/PCV) seem to be also a big issue on this platform with time/age. We will see more and more of that going forward in time I am certain of that. A tightly sealed induction system is also very important to help compressor efficiency/speeds, and wastegate actuator adjustment (and consistency across banks) is also very important.

    One post for day.

    Rob
    I have to disagree slightly, only in that we may not be seeing catastrophic failures due to overspeed but when pushing turbos past their suggested operating limits it shortens the life of the turbo significantly but putting extra stress on the internal parts that were not designed to see such speeds or maintain them for any amount of time. I agree with everything else and honestly these turbos hold up very well for how small they are and what they are asked to do, which more times than not includes pushing them past suggested operating limits.

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    Wow you werent kidding. Did the engine ingest chips?
    Most of the chips on the charge side were caught in the intake side of the IC, but I am sure some little ones got by although the engine was running fine so he dodged a bullet, most of them were getting recirculated through both turbo intakes and just pretty much wreaking general turbocharger havoc...

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    Thanks for the info Tony. This is the reason i switched from E90Post. Knowledge

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    Click here to enlarge Originally Posted by m54b25 Click here to enlarge
    Pretty much ALL the BMW Siemens ECU have ALREADY integrated the surging & choke limit model (including the compressor/turbine model) in the source code! Overspeeding a turbo like using a piggyback will cause failure!
    I wonder if that's the MAF issue the RB turbo Cobb cars were having a while back.
    Click here to enlarge
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    If you'd like a detailed failure analysis, send it to me and I'll have it done.

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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
    I wonder if that's the MAF issue the RB turbo Cobb cars were having a while back.
    I have no experience with mentioned products. Also, N54 does not use a MAF system, like the N55 units.

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    Click here to enlarge Originally Posted by m54b25 Click here to enlarge
    I have no experience with mentioned products. Also, N54 does not use a MAF system, like the N55 units.
    The N54 is Speed-density however it uses calculated MAF for several DME tables. Including the WGDC tables.
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    Nice little article. Some of the high end turbo manufacturers are including speed sensors now for the impeller as I understand it.

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    Nice article. I've never seen a turbine wheel so messed up like that one pictured.
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    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please click here for more information on legal requirements related to use of BMS parts.

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    Click here to enlarge Originally Posted by VargasTurboTech Click here to enlarge
    None of my cores were bad, I specified I wanted good cores only, but a customer brought his car in for turbos and this was one of his compressor wheels. He was running too much boost and I am suspecting overspeed as the cause. I found the turbine wheel broken at the neck and all the at the entry to the muffler at the back of the car. Literally aluminum chips were everywhere in every pipe, charge and intake, the recirc system just scattered them everywhere. I had to pull everything and have it sent out to be professionally cleaned. If you have a failure like this do yourself a failure and pull EVERYTHING or your new turbos are junk the second you fire it up.
    Wow Click here to enlarge Just exactly how much boost was he running?
    [02/07 E92 335i 6MT] - Under Construction

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    Click here to enlarge Originally Posted by fastgti69 Click here to enlarge
    Nice article. I've never seen a turbine wheel so messed up like that one pictured.
    This is the remnants from the compressor of an over-sped turbo from where I work lol
    Click here to enlarge
    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
    Burger Motorsports
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    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please click here for more information on legal requirements related to use of BMS parts.

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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
    This is the remnants from the compressor of an over-sped turbo from where I work lol
    http://www.bimmerboost.com/images/im...4_204109-1.jpg
    Here is a turbo off a powerplant we are overhauling next to a stage 2 CHRA. You can then see how big they are finished in our assembly area, next to one of my guys.

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    That's insane. I never would have thought turbos like this would be used in so many applications. Just look at the size of it! 5000hp monster?
    Burger Motorsports
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