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Re: Audis at altitude (WAS: A6 Car of the Year)

I have lived at high altitudes for more than 20 years and have been
continually impressed by how well the turbo cars do relative to the normally
aspirated ones.  I am far from an expert on the subject and I guess it
depends on how the turbo car measures and controls the intake pressure
(boost).  If the boost pressure is absolute (say, 0.5 bar) then it is
obvious that the turbo car loses a smaller percentage of it's intake charge
than the normally aspirated car as the ambient pressure decreases  i.e.  1.0
* .8 is 80% whereas (1.0 * .8) + .5 is 1.3, greater than 80% of the original
1.5 (where 1.0 is sea level pressure, .8 is the altitude multiplier and .5
is the boost add) .  Any better informed listers want to comment?  All I
know for sure is that turbos still pull hard at 11,000 feet when even the
high performance normally aspirated cars start to wheeze.
BTW, the downside is that turbo lag is accentuated by higher altitudes.

Ralph Poplawsky
'91 200Q
'95 Volvo 850 turbo 

At 10:51 AM 3/6/98 -0500, Bryan wrote:
>        Can you or someone else comment on the performance differential of
>Audi's (or other) cars at altitude?  I am curious.  So if I move to the
>mountains, which I plan to do in 5 years or so, would this effect be
>lessened with a turbo?  Let's say you live at 7,000 ft. and spend most of
>your time between 5,000 and 9,000 ft.  Both are robbed of power, but one
>more so than the other?  
>        Sorry if this is a basic question, but I know nothing about turbos.
>And what about supercharging, which is something I am contemplating as an
>aftermarket add-on, fit into this performance equation?
>        Bryan
>        V8 5 spd.