Water Cooled Turbos

[Ameer Antar]

I definitely have to disagree w/ you here...although this is 
nit-picking...Run the turbo w/o oil and you'll see how much cooling takes 
place b/c of oil. When metal rubs metal it makes heat...and oil is what 
takes away the heat....to the oil cooler. Oil is often used as a cooler, in 
engines and even in those really large transformers at sub-stations and 
industrial installations. The oil cools simply b/c it's a fluid. Any fluid 
[gas or air] has cooling affects simply b/c the molecules move around much 
more. They can get into tiny spots, take heat away from components and 
travel on to the next destination to transfer this heat. This happens in 
everything from turbos to transformers.

It's true that idling so the oil circulates cools the turbo slowly, but 
that's no reason to disregard it's affects and call it air-cooled. In fact 
I bet the water or oil cooling has the same order of affect on the turbo, 
since the oil and water usually run no cooler than 180F. So you'd have to 
call the water and oil-cooled turbos both 'air-cooled'. Only air can bring 
the temp back to 80F, but air cooling on the outside of the case is only 
part of it, since quite a bit of heat is generated in the bearing housing.

-ameer


>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