[s-cars] Oil and Turbos

[Joe Pizzimenti]

As always, great advice here, Scott.  Stay away from the chintzy radiator
oil cooler combos & get a proper 25 row cooler where the stock IC used to
live.  Don't forget to pick up a piece of sheetmetal to make some ducting.
That never hurts.

Unless you forget to bend the edges over.  Ouch.

On Wed, Mar 25, 2009 at 10:07 AM, Scott Justusson <qshipq at aol.com> wrote:

> It seems no surprise to me, and the advantage Chrysler found in
> designing the WC center bearing sections.  I spoke to one of the lead
> engineers at Chrysler when the whole WC center bearing design was
> introduced back in 1984.  As he explained it to me, you only need to
> make enough water circulate thru the system at 15psi, so that a 1600F
> bearing housing doesn't vaporize the coolant.  IIRC, in the Audi kkk,
> they document something north of 6.5 liters a minute.  WRT coking
> present, it's easy to see it at the oil lines, how do you see it at a
> piston ring?  I've seen many failures of Audi piston rings that I
> attributed to coking causing them to be extremely brittle.  Remember, if
> you hose those piston skirts with hot oil, they aren't doing much to
> cool pistons and rings.
>
> Coking is really a shutdown problem, not a running problem - the SAE
> "Severe Turbocharger Bench Test" Paper shows that even on extreme heat
> cycling the highest coking risk is a shutdown problem.  Even with WC
> center bearings, a good idea to take 2-3 minutes to allow the turbo to
> cool while the engine is running.  Chrysler actually had this
> instruction in the owners manual of the GLH turbo (no afterrun pump).
>
> I agree with an after-run pump being bypassed, it's a bad idea.  But, I
> also think that the after-run circuit in the 5kt and 200t was much more
> frequent (like for 5 minutes after every run cycle = pump and low speed
> fan) than the S car, which IME, properly functioning rarely turns on in
> comparison.
>
> WRT comments on oil temps, the SAE tests used in attaining these temps
> were pretty extreme, more so than any normal drive cycle.  Remember,
> they were evaluating turbo and oil failure, not just observing temps.
> Manny, my summary would be this:  Your observed oil temps are too high,
> and you should expect engine failure to be the result.  Put in an
> aftermarket oil cooler (Summit Racing carries Earls), I found even the
> 19row is better than a stocker, and if you are routinely
> tracking/altitude, a 36 row will make the oil temps a non issue.   With
> FMIC applications, the best spot is where the stock IC used to be.  You
> will find the 20feet of line to get there and back to be more expensive
> than the oil cooler itself, btpt.
>
> HTH and my  .02
>
> Scott J
>
> -----Original Message-----
> From: djdawson2 at aol.com [mailto:djdawson2 at aol.com]
> Sent: Tuesday, March 24, 2009 10:15 PM
> To: qshipq at aol.com; trgreen at comcast.net
> Cc: manuelsanchez at starpower.net; s-car-list at audifans.com
> Subject: Re: Oil and Turbos
>
> Interesting info...
>
> It seems almost hard to believe that you can get the hot side of a turbo
> glowing red, yet the bearing temp only sees 120C.
>
> It still seems to me that the turbo is where oil failure is most likely
> to occur, just based on years of history looking at coked/plugged oil
> return lines.  I don't dispute the facts you've presented, it just seems
> to be a more frequent point of failure... one way or the other.
>
> It's tough to read chat on the list about substituting an elbow in place
> of the after-run pump... bad choice of solution for anything other than
> getting home.
>
>
> -----Original Message-----
> From: Scott Justusson <qshipq at aol.com>
> To: 'Tom Green' <trgreen at comcast.net>; djdawson2 at aol.com
> Cc: manuelsanchez at starpower.net; s-car-list at audifans.com
> Sent: Tue, 24 Mar 2009 8:44 pm
> Subject: RE: Oil and Turbos
>
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> Audi wrote the book on all this turbo/oil stuff, specifically
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> co/authored many SAE papers on the subject, before and after watercooled
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> turbos/synthetic oils. Specific to this topic ---  See 880258 "The
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> development of a Severe Turbocharger Bench Engine Test" and 860103 "The
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> third-Generation Turbocharged Engine for the Audi
>  5000 CS and 5000CS
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> Quattro", and 970922 "Development of Modern Engine Lubrication Systems".
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> Relevant Info to this thread:
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> 860103 - Running I5 turbo motor, the temps of the piston ring with
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> watercooling are 190C, temps of the turbo bearing housing 120C.
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> Shutdown kills engines if the water circulation circuit is not
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> functioning.  Without water cooling the numbers are 260C PR and 140C
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> TBH.  On shut down, the non water cooled temps go to 360C PR and 250TBH
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> within 2 minutes of heat soak.
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> Rule:  Make sure your after run pump is working.  Regardless, some
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> idling before shutdown never hurts.
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