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Thread: Ball-Bearing Myths........

  1. #1
    Junior Member Domestic Engineer
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    Exclamation Ball-Bearing Myths........

    Just want to make a point.

    Has anybody bothered to measure the rotating assembly weight of some of the Factory Turbos ?

    I can say, coming from my background with Mitsubishi's, a Mitsubishi B16G Turbo rotating assembly weight is a little over 20% lighter than its comparable Garrett equivalent.

    Do the maths and you'll see very quickly that the MHI Unit will actually spool/respond quicker then the Garrett BB unit ever could.

    This is not even comparing the rotating Assembly weight of the newer 'reverse-Flow' B16G Turbo's which came on the late Evo's with Titanium wheels and even lighter Turbine wheels.

    Just some food for thought as I haven't seen anyone here mention this basic knowledge of Physics.


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    wire jiggler supreme Backyard Mechanic celicapain's Avatar
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    Default Re: Ball-Bearing Myths........

    hhhhhhhhmmmmmmmmm
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    Hopefully soon a 5S-GTE Chief Engine Builder MWP's Avatar
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    Default Re: Ball-Bearing Myths........

    But do BB's have a lower moving resistance than bushed bearings?
    I bet they do which makes up for the mass increases.

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    ToyotaCarClub.net Domestic Engineer Starfire's Avatar
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    Default Re: Ball-Bearing Myths........

    You're not taking in to account the drag of the plain bearing vs that of the ball/roller bearing.

    A lot more comes in to play than just mass (inertia).
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    AVGAS DRINKING Carport Converter 30psi 4agte's Avatar
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    Default Re: Ball-Bearing Myths........

    I agree.......
    Lets say the turbo has the same wheels and rotating mass but is ball bearing core.......

    Which one do you think will spool faster ?? I know where im putting my money!

    Having a ball bearing core allows you to use bigger wheel trims and still keep a decent response and hence make more power without sacrificing response.

    Not to mention a ball bearing core providing far better lateral loading capabilities and not having thrust bearing which can hurt shaft rpm when big boost is run.

    All this being said the bush bearing turbo's being made today are 10 times better than 5 years ago. They have come that far is such a short time with things like titanium etc etc so they arent dead yet !
    Last edited by 30psi 4agte; 05-07-2007 at 11:24 PM.

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    Junior Member Automotive Encyclopaedia
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    Default Re: Ball-Bearing Myths........

    20% evenly distributed is a lot different then 20% concentrated on its axis, so that 20 isn't as much as it seems.

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    Default Re: Ball-Bearing Myths........

    if your measuring the rotational mass you have to figure out where the highest% of the mass is to figure out rotational inertia.
    ie a flywheel that has 75% of its mass within 50%of its radius will spin up alot quicker than
    the same dia flywheel with 75% of its mass on the outer 50% of its radius.

    most garretts run inconel turbine wheels which will spool quiker than the equiv steel wheel as its mass is more consentrated toward the axis it spins on. this is not to mention the aerodynamics with new wheels versus old.

    i love trust turbos but there transient response is nowhere near a garret equiv.

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    Last edited by The Real Roadrunner; 06-07-2007 at 05:00 PM. Reason: cant spell at 3am

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    Default Re: Ball-Bearing Myths........

    Quote Originally Posted by allencr
    20% evenly distributed is a lot different then 20% concentrated on its axis, so that 20 isn't as much as it seems.
    That's correct.

    From Garrett's response Graph, they state at worst the time-delay being 0.3secs with a 2.0L Engine.

    I'll find some data-logged runs to get an idea of time taken to increase RPM on WOT pulls, ie more Exhaust gas to spin up heavier assemblies and maybe do a few quick sums on Sunday.


  9. #9
    how much is Too Much Toyota JustenGT8's Avatar
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    Default Re: Ball-Bearing Myths........

    Correct sizing is by FAR the biggest factor in turbo response. Most don't get this right before they start worrying about BB etc.....worrying about the 'bling' i suspect.

    Given 2 turbos equal in every way then yes BB will spool quicker but the difference is very very small. The rotational friction is actually HIGHER than a bush bearing....with a bush bearing there is no contact between the bearing and shaft, it floats in the pressurised 'shield' of oil...won't get a more frictionless surface than that.

    Where a BB comes into it's own is the improvement in the end loads on the shaft. They can take more load and this is where the friction loss is reduced compared to conventional plain bush bearings. They will take more RPM as well as a roller bearing can take more load than an oil bath so the risk of overspinning is almost non existant with BB.

    The other big difference *used* to be the new school compressor wheel designs. Up until recently, a plain bush bearing turbo was using compressor wheel design from the 70's or earlier. The BB's using new designs had a much larger efficiency island giving them a broader operating range and better low end response in airflow with reduced tendency to surge.

    With all the cheap plain bearing knocks offs around and the trend to mix and match wheels as good shaft balancing became more widespread, the plain bearing has caught up and now can be found with the new tech wheels.

    Those EVO turbos are probably the best OEM turbo out there and if you had an EVO you wouldn't touch it for sure. Not much use to the rest of us without EVOs though
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    I make people cry Chief Engine Builder Draven's Avatar
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    Default Re: Ball-Bearing Myths........

    Quote Originally Posted by JustenGT8

    Those EVO turbos are probably the best OEM turbo out there
    new 911 turbo variable vane turbos ftw
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    Default Re: Ball-Bearing Myths........

    Quote Originally Posted by Draven
    new 911 turbo variable vane turbos ftw
    I like the concept. Been tried and failed before. Watch this space but agreed there's good potential there if reliability issues have been sorted.
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    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: Ball-Bearing Myths........

    Quote Originally Posted by abently
    Just want to make a point.

    Has anybody bothered to measure the rotating assembly weight of some of the Factory Turbos ?

    I can say, coming from my background with Mitsubishi's, a Mitsubishi B16G Turbo rotating assembly weight is a little over 20% lighter than its comparable Garrett equivalent.

    Do the maths and you'll see very quickly that the MHI Unit will actually spool/respond quicker then the Garrett BB unit ever could.

    This is not even comparing the rotating Assembly weight of the newer 'reverse-Flow' B16G Turbo's which came on the late Evo's with Titanium wheels and even lighter Turbine wheels.

    Just some food for thought as I haven't seen anyone here mention this basic knowledge of Physics.

    well, titanium is actually not that much lighter then steel or nickel based alloys (the difference might less than you think),
    when you say rotating assembly, do you mean the turbine and compresor wheels only? or shafts? or?

    it would be interesting to cut one up and work out where the mass is (if you want to donate to the cause )

    and fwiw, the future is for a TiAl3 (titanium aluminide) turbine
    then again, the aerodynamics will _still_ be the largest factor affecting spool...

    i might be getting access to some proper turbines later this year. will be interesting to compare the profiles
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    Former User Conversion King Joshstix's Avatar
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    Default Re: Ball-Bearing Myths........

    I'd just like to point out that the name of this thread is about as misleading as it can get. You've called the thread Ball-Bearing Myths but then the only thing in your post is pointing out that MHI turbo's are lighter than an equivalent Garret turbo. I see nothing there really about a myth about ball bearings.

    As an anecdotal refference ATS one of the big supporters of MHI turbo's in the US for the MR2 scene who have been anti garret for a long time have dropped there TD07 line and replaced it with GT kits since they have started testing the turbo's thoroughly. Co-incidentally the vast majority of the employee's cars that were running TD06 or TD07/T67's are now running GT30/GT35 turbo kits and making more power with a more responsive power band.

    I do not put this down to ball bearings, it is simply good housing and wheel design increasing the efficiency of the turbo and good availability of the engineering info for the compressor and turbine to be able to correctly match turbo's to their usage. This is the reason why the GT series turbo's are so good, all the info is available.
    Last edited by Joshstix; 06-07-2007 at 02:24 PM.

  14. #14
    Underpowered Backyard Mechanic Moppitt's Avatar
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    Default Re: Ball-Bearing Myths........

    Quote Originally Posted by JustenGT8
    I like the concept. Been tried and failed before. Watch this space but agreed there's good potential there if reliability issues have been sorted.
    They are more widely used on modern turbo diesels, the new BMW 3l Diesel runs a garret variable vane turbo, early ones with a vacuum actuator, later ones with an electronic control for the solenoid to move the vanes. I have the cores from 2 of them that failed due to oil starvation sitting around as paper weights, although one of the compressor wheels was turned 180degrees in the housing and didnt have any fins left ( I pulled them out of the intercooler ). Also on land-rover's 2.7L turbo diesel and I suspect the 2L BMW diesels. Theye are the only two that we have ever seen fail though

    Is it the higher exhaust temperatures of petrol engines that cause the problems with variable vane turbos?

    I think they are all plane bearing turbos too. As you say justen, great concept and they work extremely well in those applications.

    The only problem is that they dont have wastegates so you cant run a screamer if your so inclined
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  15. #15
    how much is Too Much Toyota JustenGT8's Avatar
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    Default Re: Ball-Bearing Myths........

    Yeah i think it is material longevity....kinda complicated gear and tolerances are important...difficult to engineer for such a tough environment.

    More rapid and more often rpm changes with a petrol engine too so just another factor to add stress.
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