Turbo idle-down

[Phil Payne]

> >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