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Garrett & Holset Turbo Users - Your Oil Drain May Be Too Small!

Posted by JusMX141, Apr 6, 2009

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  1. JusMX141

    JusMX141 Moderator

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    Yet another possible lead on why some Garrett and Holset turbos just don't hold up on certain cars. I'm hoping to one day get to the bottom of this mystery once and for all.

    I've been noticing a strange trend among commonly-used oil drains for our cars. Read through the thread and give me your opinion at the end.


    First up, the 1G oil drain. This drain is intended to be used on 1G DSM's using a TD05H turbo, which is fed from the head with a restrictor built into the banjo fitting at the turbo. It measures somewhere around 5/8" O.D. (.572" I.D.), and works great for the turbo in which it's designed.

    OilDrain-TD05H-1.jpg
    OilDrain-TD05H-2.jpg


    Next, the 2G oil drain. This drain is all aluminum, VERY lightweight, and designed for use on the 2G DSM's using a T25, which is fed from the filter housing with a piece of 1/4" tubing and a .070" restrictor in the fitting at the filter housing itself. Obviously it will be bigger to support the additional oil flow required of the T25....it measures somewhere around 3/4" O.D. (.663" I.D.), and also works great for the turbo in which it's designed.

    OilDrain-T25-1.jpg
    OilDrain-T25-2.jpg


    Now on to the puzzling part.

    Most Garrett T3 / Holset oil drain adapters are set up to allow a piece of 5/8" hose to slide over a barbed end of the fitting and be clamped, or they use a threaded adapter to allow push-lock or Army Navy fittings to connect the drain flange to the oil pan.

    It's no secret the Garrett and Holset CHRA's require more oil- hell the oil drain hole in the bottom of the Holset center housing is almost 7/8" I.D., and the Garrett center housing has a very large drain hole as well....so why are the holes in all of the T3 / Holset oil drain adapters TINY?

    OilDrain-T3-1.jpg
    OilDrain-T3-2.jpg

    Obviously for such a tiny hole to be used on a gravity-type drain system there's going to be some obstruction. For a popular turbo that most DSMers will feed from the filter housing in order to gain the most flow and consistent pressure as many manufacturers suggest, that sure is a ridiculously small drain orifice....just over 1/2" I.D.; smaller than both the TD05H and T25 oil drains.

    Anyone have any input on this?
     
    Last edited: Jul 21, 2013

    3K  0

    1998 Mitsubishi Eclipse GST
    manual · 2G DSM

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    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

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    1992 Eagle Talon TSi
    manual · 1G DSM

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  2. T9S1i

    T9S1i Proven Member

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    Im curious as to what the factory drain line size is for a holset on a cummins truck?
    Do you have any of those around to measure, or is there anyone out there that got one with their holset to measure?

    Very interesting info though. You could have just saved many people's turbos, and lost a lot of business at the same time !! haha, its all for the greater good though.
     

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  3. turbodsm18

    turbodsm18 Proven Member

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    I dont think the hole size on a diesel necessarily matters because diesels run at lower oil pressures....This is why we must restrict oil pressure when we run these turbos on dsms.....

    -Kevin-
     
  4. JusMX141

    JusMX141 Moderator

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    I'm not trying to cut myself out of any rebuilding business....there are ALWAYS going to be turbos to rebuild. I'm just trying to get to the bottom of the brand-new turbos that die for no reason in 250 miles even though they're installed by the books.

    I don't have a Holset drain line in my possession, however I'm installing a HX40 on my buddy's 2001 Ram 2500 as soon as he gets time (works construction 12-hour days, very hard to find time to do an upgrade). I'll measure his whenever we have the HX35 removed.

    Diesels don't necessarily operate with lower oil pressures- in fact, the 15W40 oil that diesels use is a heavier weight than most street-driven DSM's use. Heavier oil will not drain as quickly.....yet the turbos in question have much larger oil drain holes in the CHRA than the flanges we're fitting to them.
     

    3K  0

    1998 Mitsubishi Eclipse GST
    manual · 2G DSM

    5K  14

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

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    manual · 1G DSM

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    manual · 1G DSM
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  5. squeak104

    squeak104 Proven Member

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    If I remember correctly the drain on my HX40 is around the size for -10 AN. My friend has made me a fitting to bolt on the bottom of the the holset and to accept -10 AN pushlock. The holes in the oil pan for bolts have been welded shut on mine and I am welding on a -10 AN socket as well. The hole in the pan is going to be the same size as the drain of the holset. As long as all the holes are the same size if not bigger than the holset I'll feel comfortable with it.
     

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  6. JusMX141

    JusMX141 Moderator

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    A very wise move. You're paying attention to your turbo's requirements, and you'll probably be rewarded with great service and longevity.

    I'm under the assumption that the guys who are having trouble with blowing these turbos repeatedly are buying generic mass-produced oil drain and supply hardware....hardly anyone's paying attention to their turbo's needs.


    The truth is if you're firing 80psi of high-volume oil pressure into one of these turbos, you can't expect it to drain properly through a 1/2" fitting. The result is the oil will dam up inside the center housing and eventually work it's way past the seals, ruining the turbo.
     

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    1998 Mitsubishi Eclipse GST
    manual · 2G DSM

    5K  14

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

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    1992 Eagle Talon TSi
    manual · 1G DSM

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    manual · 1G DSM
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  7. need2boostpsi

    need2boostpsi Proven Member

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    makes since to me, but if the oil drain wasnt large enough seems it would push oil into the compressor inlet and turbine housing? that would be the first sign thats there is something wrong with A) oil inlet pressure, or B) oil drain issure. My extreme PSI kit has a rather large drain hole from what i remember. i know i could stick my pinky in it LOL
     
    need2boostpsi

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  8. jking29

    jking29 Proven Member

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    That looks like the same fitting I bought for my Holset. I also noticed the difference in size between it and the oil outlet on the chra. I took a Dremel and beveled out the drain hole in the fitting to match the oil outlet. Oil definitely does not like sharp edges when it comes to drain back! I'm feeding from the head so hopefully I won't have any problems with it.
     

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    1991 Eagle Talon TSi AWD
    automatic · 1G DSM
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  9. JusMX141

    JusMX141 Moderator

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    Information taken direct from the Holset service manual for the HX35/40:

    Oil return pipes are permitted to decline at an overall angle of not less than 30 degrees below horizontal. All turbocharger applications require a pipe of internal diameter greater than 19 mm which has integrated connectors. To ensure oil drains into the engine under all operating conditions, the return connection into the engine sump must not be submerged and the outlet flange of the turbocharger must be 50 mm above the maximum oil level of the engine sump pan.


    .525 " = 13.335 mm, which is WAY under the minimum required drain size for a Holset turbo. If you're using this fitting on your Holset, it's almost certainly going to restrict the oil drainage....possibly putting your turbo at risk for premature failure.

    I think I'm on to something.
     

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    1998 Mitsubishi Eclipse GST
    manual · 2G DSM

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    manual · 1G DSM

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  10. jking29

    jking29 Proven Member

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    Hmmm. Thanks for that. Looks like I'm redoing that with -10an before I start driving it this year.
     

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  11. JusMX141

    JusMX141 Moderator

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    Don't rush out and buy a full -10AN setup just yet....it doesn't appear to be any bigger than the fitting I examined.

    IMG_1004.gif
     

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    1998 Mitsubishi Eclipse GST
    manual · 2G DSM

    5K  14

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM

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    manual · 1G DSM

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    1993 Eagle Talon TSi AWD
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  12. jking29

    jking29 Proven Member

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    No if I go -10an I will take a piece flat stock and use a weld bung as well as a weld bung on the pan.
     

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    1991 Eagle Talon TSi AWD
    automatic · 1G DSM
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  13. turbodsm18

    turbodsm18 Proven Member

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    -10an drain flange bought from extreme psi......Restriction???

    [​IMG]

    [​IMG]

    -Kevin-
     
  14. gsxtasy

    gsxtasy Proven Member

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    Isn't -AN measured in 1/16th's of an inch. -10 AN is 10/16=5/8''=15.87mm. Or am I off on that? This has struck my interest as I'm preparing to install my new BW and also have the -10 drain setup.:hmm:
     

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  15. jking29

    jking29 Proven Member

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    So 19mm is approximately 3/4", that would mean at least -12an per Holset, correct?
     

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    1991 Eagle Talon TSi AWD
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  16. dsm-onster

    dsm-onster DSM Wiseman

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    Holsets do have bigger shafts. This gives there oil seals more surface area in contact with oil pressure. I wouldn't be suprised that improper drainage could raise the chances of oil blowing past the seals.

    But, what is interesting is that the OEM drainline flanges for t3 journal bearing garretts (volvo, turboford, k-car, GN) all have 15/32" or .46875" diamater drain holes. While the garrett t3 outlet for my turboford t3 turbo in front of me has a square drain hole out of the chra that measures the same as my h1c, .59375" X .46875" . Why would the drain hole on the garrett chra be larger than the drain hole for the oem flange that attaches to it?????
     

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  17. Ravenous

    Ravenous Proven Member

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    I'm currently in the process of rebuilding my HX-35. I don't have an oil drain setup yet for it, should I weld in a 12AN bung on it? I was waiting for the turbine housing kit to come back in stock at theturbotrader for ease of setup but if I have to change the drain line anyway I can get the housing quicker from another source and piece the setup together. I need a new oil pan anyway so maybe I'll just do 12AN there instead of an adapter as well.
     

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    manual · 1G DSM
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  18. spoonman

    spoonman Supporting VIP

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    I have fabricated many oil drain flanges for my turbos and close friends, I usually try to make the oil drain line and flange around 1 inch I.D. usually slightly smaller. I always believed that bigger is better in the case of oil drain lines.
     
  19. Morphius

    Morphius DSM Wiseman

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    You should of posted this in the oiling thread that already exits.
     
  20. need2boostpsi

    need2boostpsi Proven Member

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    this thread doesn't just pertain to holsets, so why put it only in the "holset oiling thread"?
     
    need2boostpsi

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    11.506 @ 125.280 · 1G DSM
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  21. WIDSM

    WIDSM Proven Member

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    Does anyone know the size of the hole in the oil pan? I just looked at my return line for my holset and it looks like .500 so I guess I'll be drilling it out.
     
  22. talonDSMerr

    talonDSMerr Proven Member

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    Everyone has been worrying about a restrictor for the oil feed, but the real problem could be caused by this! Too small a drain hole would dramatically increase oil pressure inside the turbo, no matter what size the oil feed restrictor is...
     

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    1991 Eagle Talon TSi AWD
    · 1G DSM
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  23. caged

    caged Proven Member

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    Iv always wondered if poor crank case breathing could also worsen it by pressuring the crank case.
     
  24. bluegs03

    bluegs03 Proven Member

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    please please keep us updated on this jusmx141, if you could give us a recommended course of action such as make sure your drain fittings are at least 19mm wide that would be great. Thank you for all the possible turbos you might have saved!
     
  25. Brianawd

    Brianawd Proven Member

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    No they don't. A 5.9 and a 8.3 will both see oil pressure around 80-90psi at 3k warm. I have see them peg my 100psi gauge when cold. Most all diesel run high oil pressure for the rpms they turn. A 12.7 Detroit will see 60-70psi at 2100rpms when warm.
     

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    1992 Mitsubishi Galant VR-4
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