Water Cooled Turbos

[Simon Allcorn]

I thought the main reason behind letting the engine idle for ~1 minute after
coming to a stop was to let the speed if the turbo slow to a reasonable
amount with oil pressure still there because the turbo bearing need's oil
pressure the same way a big end does ? 

> -----Original Message-----
> From:	isham-research.freeserve.co.uk at pop.pol.net.uk
> [SMTP:isham-research.freeserve.co.uk at pop.pol.net.uk]
> Sent:	Wednesday, February 14, 2001 12:00 AM
> To:	Dave.Eaton at clear.net.nz; quattro at audifans.com
> Subject:	RE: Water Cooled Turbos
> 
> > can't resist a smile at the inclusion of sae papers in this context, but
> i
> > digress....
> 
> Some of them are interesting, like the graph of component temperatures
> after engine shutdown for air-cooled and water-cooled turbos included as
> Figure 9 in Audi's SAE 860103.
> 
> Full SAE library reference is 0148-7191/86/0224-0103$02.50
> 
> P.S. Yes, air-cooled and not oil-cooled.  Oil plays no major part in
>      heat removal - the key is airflow.  The way to cool a non-water
>      cooled turbo is not to stop and idle the engine for 40 seconds,
>      but to coast for the last 40 seconds of the trip and shut the
>      engine off when you arrive.  With the car stationary, there's no
>      airflow over the turbo and it cools mainly by radiation and
>      convection, i.e., slowly.
> 
> --
>  Phil Payne
>  http://www.isham-research.freeserve.co.uk/quattro
>  Phone +44 7785 302803   Fax: +44 7785 309674