[s-cars] installing a hybrid turbo

Stephen Redford shr42 at msn.com
Wed Aug 2 13:46:42 EDT 2006 


---------- Dave , I need a new turbo for my '85Urq , the old one is really smoking a lot , I was going to go with a Garrett of some kind. I have yet to study the maps of the Garrett's.   Do you think that the Garrett T03/T04 , which you mention , would be a good choice for me...  The '85Urq now has Megasquirt EFI  and is getting a new intercooler ... by the way , I gained about 56Whp and 63 Ft-Lbs torque from the efi install... It is a totally different car .. This was on a Mustang Dyno .. But the Turbo  has to be replaced and I have come to terms with having to change the exhaust maifold to fit A new turbo.  That 50 trim sounds good ...     TIA ,   Stephen Redford



  ----- Original Message ----- 
  From: djdawson2 at aol.com<mailto:djdawson2 at aol.com> 
  To: Jeff.Postupack at analog.com<mailto:Jeff.Postupack at analog.com> ; s-car-list at audifans.com<mailto:s-car-list at audifans.com> 
  Sent: Tuesday, August 01, 2006 9:36 AM
  Subject: Re: [s-cars] installing a hybrid turbo


  To supplement Jeff's comments with some Garrett speak...
   
  Ball bearings have a bad time dealing with vibration.  A turbo that surges, subjects the bearing to some "bad stuff" typically leading to a short life.  A floating journal bearing can deal with it much better, as it typically has 2 "layers" of fluid to dampen the vibration or disturbance.  A ball bearing is rigid in its design, and vibration will make it die quickly.
   
  As the turbo wears, some things happen that *will* make it out of balance.  Objects in the intake will chew up the blades on the compressor wheel.  At that point, both surge and vibration are working against the ball bearing.
   
  What Garrett has done...  create a ball bearing system that has the advantages of both a ball bearing, and a journal bearing.  The ball bearing cartridge itself is damped by fluid.  The cartridge is pinned in place (it can't spin), but there is clearance between the bearing housing and its bore, and oil pressure is present in the clearance, providing some damping ability.  It is, in essence, a floating ball bearing.
   
  Ball bearing attempts in turbo applications have failed on every attempt in the past.  This latest and greatest from Garrett seems to be doing OK... provided you do not have surge.  My first GT30R used a .63 turbine housing.  As a result, I had too much boost... too soon for the characteristics of the compressor.  As a result, I had substantial surge, and the turbo lived only 22k miles before the bearing literally fell apart.  I have changed to a .82 turbine housing.  Surge is nearly eliminated, but it can happen under certain circumstances.  This turbo now has about 26k miles on it, and honestly, I'm simply waiting and expecting its failure.
   
  The sad part about these new turbos, is that Garrett has elected to make them non-servicable.  You can not replace the bearing, or service it in any way.  If the bearing was replaceable, I would be much more likely to suggest them to anyone willing to take on the additional maintenance task of periodic bearing replacement.  As a result, when the bearing does fail, it ruins every component of the turbo.  When the shaft comes free, the compressor and turbine blades chew up the inside of both the turbine and compressor housings... rendering your $1100 - $1500 turbo 100% totaled.
   
  They are great performing turbos, but you have to decide for yourself if they are worth the additional effort and expense.  If you're thinking you're going to bolt up a GT ball bearing turbo and drive it for 200k miles (like a journal bearing KKK), you will be disappointed.
   
  Dave
   
   
  -----Original Message-----
  From: Jeff.Postupack at analog.com<mailto:Jeff.Postupack at analog.com>
  To: s-car-list at audifans.com<mailto:s-car-list at audifans.com>
  Sent: Tue, 1 Aug 2006 8:31 AM
  Subject: [s-cars] installing a hybrid turbo




  Further to what  Dave wrote.. 

  I consulted with a machinist who worked in the aircraft business his
  entire life.
  Having seen ball bearings, bushings in various applications.he told me 
  "A journal bearing  is a cylinder which surrounds the shaft and is
  filled with some form of fluid lubricant Journal bearings can have
  unlimited life, compared to a ball bearing."
  ->. For the more complete write up, seek
  http://www.reliabilitydirect.com/appnotes/jb.html<http://www.reliabilitydirect.com/appnotes/jb.html>

  He (the machinist)  also commented that journal bearings are much
  tighter tolerances composed of particular material much better suited to
  the 
  Hot side and cold side of the turbo charger.,  than a ball bearing will
  ever be.

  All the fascination with ball bearings may be misguided for a long life
  expectancy,  turbo application.

  Truth be told a journal bearing can be machined to very close fitment,
  which means the shaft will not wobble.
  Isn't that what the Audi R&D actually specified also?

  Which means when I get around to selecting a turbo, for long life and
  higher boost, it shall have a journal bearing.

  Posto


  ------------------------------

  Message: 2
  Date: Tue, 01 Aug 2006 00:48:31 -0400
  From: djdawson2 at aol.com<mailto:djdawson2 at aol.com>
  Subject: Re: [s-cars] installing a hybrid turbo
  To: calvinlc at earthlink.net<mailto:calvinlc at earthlink.net>, tedebearp at yahoo.com<mailto:tedebearp at yahoo.com>,
      james.pasqualoni at gs.com<mailto:james.pasqualoni at gs.com>
  Cc: s-car-list at audifans.com<mailto:s-car-list at audifans.com>
  Message-ID: <8C8833CDFAF9FD8-D28-A04D at FWM-D43.sysops.aol.com<mailto:8C8833CDFAF9FD8-D28-A04D at FWM-D43.sysops.aol.com>>
  Content-Type: text/plain; charset="us-ascii"

  1) the journal bearing units are inexpensive
  2) I haven't seen the journal bearing units fail (genuine Garrett, not
  ITS, etc...)
  3) I *have* seen many of the GT units fail
  4) if your hp goals are 400whp or less, why bother with a ball bearing
  unit?
  5) a 50 trim allows a lot of boost at low rpm without surge issues
  6) the GT units seem to be much more prone to surge
   
  IMHO, there's a lot of trouble-free hp available from a 50 trim T3/T4.
  Great drivability, low boost threshold, low cost.  In fact, the 50 trim
  compressor is about the most versatile thing I've ever experimented
  with.
   
  OTOH, I run a 30R... but I wanted "more."  But, as a result of this
  choice, I'm on turbo # 2 in 50k miles, and under certain circumstances,
  I do have surge.
   
  Dave
   
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