Garrett BB CHRA pressure differential from loose V-Band housing cause oil leak - Miata Turbo Forum - Boost cars, acquire cats.

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Old 01-20-2016, 12:15 AM   #1
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Default Garrett BB CHRA pressure differential from loose V-Band housing cause oil leak

I noticed that my Tial V band housing had some play in it. Not the vband side but the CHRA side with the 3 half moon clamps and 6 iconel bolts side. I've been meaning to take it off and re tighten it all but got lazy.
Sunday night pulling into the garage I saw underhood smoke. Took a look and found oil in the intake and airfilter.
Pulled the airfilter and started it today. Idle wasn't bad but revving it caused oil to push past the intake impeller. Got scared - like moving to Bel Air scared.

Pulled the turbo. Drain was clear and fine.

Only real variable that changed in the last many months was cold cold weather and am assuming an ever loosening hotside housing.
Since the hotside when tightened pushes the CHRA and some multi beveled washer in I'm assuming it being loose allows pressure to escape or worse oil??

Taking it apart I noticed hotside definately had play and 1 Iconel bolt had loosed right out up against the drain adaptor and was actually gouging it a bit.

Everything is buttoned back up and the 6 little Iconel v band bolts are torqued to the max with red locktite ( I know it will probably disintegrate at turbo heat levels but it made made feel good using it)

I'll start in up tomorrow late afternoon and see what happens but any guesses on the oil leak? Was it a pressure differential issue?
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Old 01-20-2016, 12:23 AM   #2
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iirc loose hotside usually gets oil leak into the turbine, not the compressor side. perhaps your restrictor is too big?
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Old 01-20-2016, 12:31 AM   #3
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It could be. This happened so sudden though. Colder less viscous oil definately gives more oil pressure but today I started it in a heated garage.
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Old 01-20-2016, 12:42 AM   #4
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BTW does a Garrett BB CHRA have all metal seals? I wouldn't think that silicone/rubber seals could survive in there?

Since I'm running BE pump pump and no oil squirters and have amazing oil pressure (don't ask me to quantify that since my OP sender died when I replaced the clutch) how small of of a restrictor have you seen used successfully on a GT28 framed turbo (I have a disco)
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Old 01-20-2016, 12:44 AM   #5
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A. Oil requirements depend on the turbo's bearing system type. Garrett has two types of bearing systems; traditional journal bearing; and ball bearing. The journal bearing system in a turbo functions very similarly to the rod or crank bearings in an engine. These bearings require enough oil pressure to keep the components separated by a hydrodynamic film. If the oil pressure is too low, the metal components will come in contact causing premature wear and ultimately failure. If the oil pressure is too high, leakage may occur from the turbocharger seals. With that as background, an oil restrictor is generally not needed for a journal-bearing turbocharger except for those applications with oil-pressure-induced seal leakage. Remember to address all other potential causes of leakage first (e.g., inadequate/improper oil drain out of the turbocharger, excessive crankcase pressure, turbocharger past its useful service life, etc.) and use a restrictor as a last resort. Garrett distributors can tell you the recommended range of acceptable oil pressures for your particular turbo. Restrictor size will always depend on how much oil pressure your engine is generating-there is no single restrictor size suited for all engines. Ball-bearing turbochargers can benefit from the addition of an oil restrictor, as most engines deliver more pressure than a ball bearing turbo requires. The benefit is seen in improved boost response due to less windage of oil in the bearing. In addition, lower oil flow further reduces the risk of oil leakage compared to journal-bearing turbochargers. Oil pressure entering a ball-bearing turbocharger needs to be between 40 psi and 45 psi at the maximum engine operating speed. For many common passenger vehicle engines, this generally translates into a restrictor with a minimum of 0.040" diameter orifice upstream of the oil inlet on the turbocharger center section. Again, it is imperative that the restrictor be sized according to the oil pressure characteristics of the engine to which the turbo is attached. Always verify that the appropriate oil pressure is reaching the turbo. The use of an oil restrictor can (but not always) help ensure that you have the proper oil flow/pressure entering the turbocharger, as well as extract the maximum performance.
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Old 01-20-2016, 12:50 AM   #6
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I do remember reading that and running a restrictor. Maybe it's time to go all Boa on it. I'll have to custom make one then.


Soon I'll be posting "oil starved turbo for sale, slow to boost hard to leak"
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Old 01-20-2016, 12:54 AM   #7
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EDM drill and safety wire your CHRA-turbine hardware before you wreck a CHRA/turbine housing.
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Old 01-20-2016, 01:09 AM   #8
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That is the best case solution. I'm in Canada so it may cost as much as a CHRA !

What are the avg costs of that process, I assume it is per bolt and Iconel is probably more expensive than Ti drilling?
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Old 01-20-2016, 04:17 AM   #9
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Quote:
Originally Posted by Landrew View Post
That is the best case solution. I'm in Canada so it may cost as much as a CHRA !

What are the avg costs of that process, I assume it is per bolt and Iconel is probably more expensive than Ti drilling?
I had 6 inconel bolts done for ~$120 I think. This was a long time ago and I don't know if that was a good price.

i suck at safety wiring but its kind of a tight fit.

EDIT: I'm beginning to doubt that price but i know for sure its around 100.

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Old 01-20-2016, 04:47 AM   #10
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Machine shop at work has am EDM machine. I need to get to be buds with the operator.
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Old 01-20-2016, 09:02 AM   #11
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I charged $80 if you didn't get the bolts from me and used $3.36 mcmaster 3202A44 TiAlN coated HSS drill bits, a rigid fixture, a bridgeport, and fancy cutting fluid. I would get 3 bolts per drill bit. Well...4.5 or so but the drill bits were much cheaper than the bolts. I have a few inconel bolts with broken bits in them still. I could get all 6 drilled in a lunch hour.
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Old 01-20-2016, 03:00 PM   #12
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$100 is a perfectly fair price to pay. I paid a local machinist to do mine (7 years ago) and when I picked them up, their parting words were "Don't ever bring anything like that here again".
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Old 01-20-2016, 06:35 PM   #13
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Quote:
Originally Posted by Savington View Post
Their parting words were "Don't ever bring anything like that here again".
I could see that.
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Old 02-15-2016, 05:12 PM   #14
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Sorry for not reporting back much much sooner. Like the person who only calls when they need a favor or only prays when they need help I should have communicated my results and thanks sooner.




All back together and no more oil cloud. Could have been my original homemade restrictor or the loose hot side. Either way I'm happy that there was nothing major to replace.
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