Turbo idle-down & consequences

[superba]

Hi All,

My dinosour, aka 81 5KT > 330K miles, has had the turbo replaced 2 times.
It's an "oil cooled" only type, but certainly ram air has some effect.  The
first time the turbo was replaced it was on Audi and I didn't see any
components.  The second time I replaced it by mistake at ~260K miles;  the
actual culprit was a blocked cat converter.

When I replaced the turbo, the rebuilder tried to get me to install new
inlet and outlet oil lines, but I didn't, for they weren't coked or blocked
in any way.  The worst part was the baked on oil black color.

Anecdotally, my experience reinforces Phil's opinion that cooling down is
not necessary.  I was advised very early on by Paul Lange, GM at Anderson
Behel Porsche Audi, that I ought to idle for about one minute before
shutting down the engine.  Like most others I was not very disciplined in
doing that.

I've observed my turbo when it was glowing red(at night) and I wouldn't
advise shutting down in that condition.  However, driving with no
appreciative boost for a few miles circulates the oil enough and the
ram/ambient air helps to cool it, and I see no reason to idle it for a
minute after parking.

HST, changing the oil and filter(s) and using the correct grade of oil plays
a large part in the process.  Many engines get sludged up that have no
turbo.

My .015 worth.

Cheers!

Jim Jordan

>  Message: 1
>  Date: Thu, 15 Jan 2004 12:35:24 +0000
>  From: desmo888 at comcast.net
>  Subject: Re: Turbo idle-down
>  To: "Phil Payne" <quattro at isham-research.com>
>  Cc: , quattro at audifans.com
>  Message-ID: <011520041235.16578.4bd2 at comcast.net>
>
>  Great info Phil.
>
>  The only time I would "idle down" is if running the car hard
>  immediately before pulling in to the driveway.  The high temp of
>  the turbo (after high boost) would cool down to the static temp
>  (which is above cruise temp per Phil but still below full boost temps).
>  This would limit the possibility of the oil left in the bearing
>  at shut down being cooked my an ultra hot turbo.
>  I word it as should/would/could is because I
>  shant/wouldn't/couldn't think of parking a turbo car before a
>  couple miles of cool down...
>  I have always thought the turbo timer to be a complete waste on money.
>
>  Dave K.
>  '90 CQ - not turbo but will be later this year...