Turbo idle-down

desmo888 at comcast.net desmo888 at comcast.net
Thu Jan 15 07:35:27 EST 2004

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...
> > >You need airflow to cool the turbo, and there is no airflow if the car is
> > stationary - except
> > >the paltry contribution of the alternator fan.
> > I must respectfully disagree that it is "EXACTLY" wrong, for these reasons:
> > 1) Idling the turbo down for a few seconds assures that it's no longer
> > spinning at high revs when you kill the engine, just in case you did goose
> > the engine when pulling into your home. This is A Good Thing in itself, and
> > makes idling the car for a few seconds worthwhile.
> a) Attach a pyrometer to the turbo hot side.
> b) Get the car up to a sustained 100+ mph for at least five minutes.
> c) Turn off and cruise at 50 mph for ca. one and a half miles.
> d) Arrive home and park in the drive.
> The last time I did this was about five years ago.  The turbo casing temperature 
> peaks when
> you drop for the off-ramp.  Then it gradually declines until you hit the 
> driveway.  After you
> park up, it rises again.
> This was on my MB - an MC-1 engine in an ur-quattro.
> --
>   Phil Payne
>   http://www.isham-research.com
>   +44 7785 302 803
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