"scsilverdak" <scsilverdak@hotmail.com> wrote:
: My testing of my Dakota this past summer has yielded a few questions, just
: how much does the altitude of a dragstrip have an effect on the way a car or
: truck will actually perform?
: Say given that the weather and track conditions of 2 different tracks were
: the same, but the track with a altitude closer to sea level would enable
: said car or truck to ET better due to better air quality.
: Is there a correction factor that would give some idea
: how a car or truck would perform at a lower sea level?...........or am I
: just nut's thinking the Dakota
: would run better a lower level track?
: Keystone has altitude of 1500ft above sea level, I'm betting the Dakota
: would ET better at a track with a level of around 500-800 ft.
This is almost a religious issue with some folks ;-) but here is
my take on it...
I ignore elevation because elevation itself doesn't have an effect
on your performance. Where elevation does come into play is with the
air density - the higher you go, the less the "column of air" pushing
down on you weighs, and the less the air pressure. However, this is
nothing more than barometric pressure. This is why I ignore elevation
and base everything on weather readings (temp, humidity, barometric
pressure)
A little example might be more enlightening... Say you went to
a sea level dragstrip and made a pass. At the time you made the run,
the temp was 60 degrees, 50% humidity, and a barometric pressure of 30".
Now, you go to a strip where everything is identical except this one
is at 5,000' elevation. The temp is 60 degrees, you have 50% humidity,
and tha barometer is reading 30". For the sake of argument, imagine
that everything else is exactly the same as the other run (track surface
and truck condition, etc.) Would you expect to run faster, slower, or
the same as before? The answer is the same - even though the elevation
is much higher which is detrimental to performance, the local weather
conditions compensated and raised the barometric pressure up to the same
pressure as at the sea level track.
This is why I don't pay any attention to elevation - although it
does have an effect on barometric pressure, I read the pressure
directly off the barometer, and I don't care a bit about what
is contributing to that pressure, all I care about is the end
result.
Another way of looking at this from my perspective would be to
consider running at a strip where the air temp is 80 degrees.
Suddenly some clouds roll in and the temperature starts to drop.
Do you run for a light meter or a cloud chart to try to extrapolate
how much effect these clouds are having on the air temperature?
No - you just read the thermometer. That's all you care about -
the end result. Likewise, elevation is simply a factor, like the
clouds were simply a factor. All you need to be concerned with
is the end result, and reading the barometer will give that to you.
I don't like to use elevation, because it can be misleading. It
is only one of the factors that contributes to your overall performance;
temperature and humidity are important as well. Using the actual
temp, humidity, and barometric pressure readings, you can use
conversion factors to correct your ETs to "standard" - elevation is
simply not a factor for anyone who has a barometer. (And anyone who
is trying to "correct" their times without a barometer, relying simply
on elevation is only fooling themselves - garbage in, garbage out.)
That said, in general, yes, you will run slower at higher elevations.
:-)
---Jon-
.---- Jon Steiger ------ jon@dakota-truck.net or jon@jonsteiger.com -----. | I'm the: AOPA, DoD, EAA, NMA, NRA, SPA, USUA. Rec & UL Pilot - SEL | | '70 Barracuda, '92 Ram 4x4, '96 Dakota, '96 Intruder 1400, '96 FireFly | `----------------------------------------- http://www.jonsteiger.com ----'
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