[s-cars] installing a hybrid turbo

Stephen Redford shr42 at msn.com
Wed Aug 2 17:35:07 EDT 2006

------ Dave , thanks for the info ,  I am not clear what you mean about a ,  T03/T04 turbo ... Is it a kkk with a garrett compressor cold side , or does Garrett supply the hot side, the T3 and  the T4 - 50 trim compressor side also , I thought they only did ball bearing turbos ?   If you are favoring a T3/T4 turbo , for the street ,  is that a complete bushing turbo ?  You said that you did not care for the kkk/Garrett combo, because it did not work "optimally together...  If I get it right , the T3/T4 complete bushing turbo is what I want , Even if it means modifying the exhaust manifold    ...Stephen

  ----- Original Message ----- 
  From: djdawson2 at aol.com<mailto:djdawson2 at aol.com> 
  To: shr42 at msn.com<mailto:shr42 at msn.com> 
  Cc: s-car-list at audifans.com<mailto:s-car-list at audifans.com> 
  Sent: Wednesday, August 02, 2006 1:58 PM
  Subject: Re: [s-cars] installing a hybrid turbo

  Plain and simple... the 50 trim works very well on a 2.2.  I have tried the 50 trim with stage 1, 2, and 3 turbine wheels.  The neat thing about a 50 trim, is that it is capable of moving a "nice" quantity of air, and has superior surge characteristics.  A 50 trim with a stage 1 responds very quickly.  It is a nice solution for folks at altitude, however, I would not use it if you are at sea level frequently, because it will *probably* build too much boost too soon, and surge as a result.  If your boost levels are limited to 15-16 psi, a stage 1 would work fine, because you are operating in the meat of the compressor map.

  By looking at Garrett compressor maps, it could be easy to arrive at the conclusion that the 50 trim is too big.  I arrived at this same conclusion, and did some experimenting with the 46 trim.  The problem is, is that the 46 trim does not tolerate high boost at low flow levels... and that is what our Audis are all about.  Garrett maps indicate that their design concerns were focused on engines running at 15psi or less.  Many of us are operating at levels approaching 30psi.  Therefore, we have to select a compressor that can tolerate high boost vs. low flow.  When it comes to the Garrett T04E, there seems to be only 2 choices: the 50, and the 57.  The 50 trim, in practice, tolerates a very wide range of operating conditions... making it the ideal choice.

  One of our local guys (Ben Howell) is running a 46 trim with a stage 5 wheel, in an efi 2.5.  All I can say is "stunning."  However, the jury is still out on its performance if the wick is turned up.  As long as it has been running, he's been running about 14-15psi... exactly what the Garretts were designed for.  Peak hp was 380-390whp,  but it had a torque curve like a small block chevy.  Now that is fun to drive.

  For some folks (myself included), the 50 trim isn't adequate because it isn't capable of moving enough air to go past 400whp.  However, with the reliability issues prevalent with the GT turbos, I may rethink that down the road.  If there were a journal bearing 3071 or 30R (and there will be someday), I'd be a buyer.  The GT30R seems to be the 50 trim of the "new" Garrett world... having an exceptional map, and extraordinary efficiency.

  EM's... you don't have to change to a different manifold.  I'm assuming you're talking about a 10v engine.  You can get a hydrid that uses a KKK hotside.  Javad is having numerous hybrids made for him at this point, and I'm sure you could have him obtain yours.  However, I've arrived at the conclusion that a Garrett just doesn't operated optimally with a KKK hot side adapted to it.

  For some good efi/10v ideas, Javad would be good to talk with, as well as Jim Green.  Jim, however, was running big stinking/surging turbos, seeking very high output... so he was OK with a turbo that was complaining below 4krpm.  But he did get impressive results from a tired 10v.

  For me, for the street, it would be a 50/stage 2.

  -----Original Message-----
  From: shr42 at msn.com
  To: djdawson2 at aol.com
  Cc: s-car-list at audifans.com
  Sent: Wed, 2 Aug 2006 11:46 AM
  Subject: Re: [s-cars] installing a hybrid turbo

  ---------- 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<javascript:parent.ComposeTo('djdawson2 at aol.com');> 
    To: Jeff.Postupack at analog.com<javascript:parent.ComposeTo('Jeff.Postupack at analog.com');> ; s-car-list at audifans.com<javascript:parent.ComposeTo('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.
    -----Original Message-----
    From: Jeff.Postupack at analog.com<javascript:parent.ComposeTo('Jeff.Postupack at analog.com');>
    To: s-car-list at audifans.com<javascript:parent.ComposeTo('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

    He (the machinist)  also commented that journal bearings are much
    tighter tolerances composed of particular material much better suited to
    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.



    Message: 2
    Date: Tue, 01 Aug 2006 00:48:31 -0400
    From: djdawson2 at aol.com<javascript:parent.ComposeTo('djdawson2 at aol.com');>
    Subject: Re: [s-cars] installing a hybrid turbo
    To: calvinlc at earthlink.net<javascript:parent.ComposeTo('calvinlc at earthlink.net');>, tedebearp at yahoo.com<javascript:parent.ComposeTo('tedebearp at yahoo.com');>,
        james.pasqualoni at gs.com<javascript:parent.ComposeTo('james.pasqualoni at gs.com');>
    Cc: s-car-list at audifans.com<javascript:parent.ComposeTo('s-car-list at audifans.com');>
    Message-ID: <8C8833CDFAF9FD8-D28-A04D at FWM-D43.sysops.aol.com<javascript:parent.ComposeTo('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
    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
    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.
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