You know, folks, I just used the calculator url supplied by Jim. It is
pretty
cool. It can be simplified a bit though. If you know your hp at a set of
given conditions (leave out humidity), then find the air density for that hp
number in whatever units you are using. Then calculate the density of the
air at whatever the new conditions are, again leave out humidity. Then your
new hp is just the old hp times the ratio of the 2 densities.
hp2 = hp1 *(rho2/rho2)
rho is density = (P *144) / (g * R * (460 + T))
P = air pressure in psia
g= gravity constant = 32.174
R = Universal Gas Constant = 53.3
T = Temp in Deg F
I did this a couple of times using the calculator for 3 different humidity
levels and using 95 Deg F, Baro of 26.5" hg (12.6 psia), 0%, 30%. and 50 %
Rh numbers. If I use 30% as baseline reference, then hp changes by 1.9% if
the humidity drops to 0% and only 1.3% if it rises to 50%. So just forget
trying to compensate for humidity unless you are running a submarine...
It really is easy to find how much to derate you motor for B'ville given
dyno sheets at some reference set of atmosphere numbers and how much to
detune by jet changes (must use flow area of the jet or pill though).
IMHO....YMMV
mayf
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