Performance 101,
sort of generic
as long as
track temps
(not the air temp)
are above 70*f & below 120*f
(usually air temp less than 85*f or above like 55*f)
altitude make track surfaces heat up quicker too
(closer to the sun)
RAD (
relative
air
density corrected altitude) corrected altitude
combined barometric pressure & altitude/elevation combined
is below 2500-3500ft altitude/elevation (marginal air)
between 90 grains of water per million & like below 120-ish/gpm
higher end it shouldn't be too bad, 1-3 tenths loss possibly,
depending on HP levels
the closer to full-on race combo, more on the edge,
the more it will be noticed
more RAD/corrected altitude/elevations = less power
you can tune some of that back in,
when the Altitude/elevation goes up
the BTDC timing goes up
Altitude/elevation up
the carb jetting goes down smaller #'s (leaner)
(with FI {especially mech. FI}, you
bypass more fuel off to lean it down)
altitude/elevation goes up
compression goes up (thinner head-gaskets or even camshaft timing)
& visa versa
good air lower altitudes
bigger #'s jetts with good air & smaller bypass pills in FI
(fatten it up)
back of timing a lil' too, usually several degrees (like 3-4*'s)
(even can take away some compression, thicker head gaskets,
not really necessary in some/most cases, depending on fuels used etc.)
blown combos you need more overdrive %
'spinning the blower faster" than the crankshaft by %
a smaller pulley on top &/or a larger pulley on the bottom
makes more boost
thinner head gaskets & more compression helps too
the air is thinner, it will starve for air, timing & compression
chutes will deploy slower too, lack of air molecules
turbo cars don't like to spool up at severe altitudes,
you need or could use N2O (or CO2) to help it spool faster
just because you're at 1500' base 'actual altitude
doesn't mean the RAD air is at that range,
you can have a 3,000 to 5,000 ft
RAD change, up or down, it is most often much higher/up (RAD)
with less air, more grains of water
it's
not often less than altitude/elevation than
your actual altitude
but;
sometimes at or near sea level tracks, it can be below sea level
& when it is
that's mineshaft air, really good air
better air, better tracks mostly too
usually comes with some cloud cover & cooler air temps,
far less humidity
it's really really good air for making HP
'
at that specific altitude' that day
even more, noticeable if you race at someplace like
Morrison Co. Bandimere Speedway, with a base altitude of 5800+ ft
I've raced there when it was RAD corrected altitude at 12,000ft
The car/engine feels like a turd, seriously down on power
even with timing in it & leaning it out & more compression
Roots or centrifugal Blower can overcome some of it,
but even they will be slower
N2O cars like cool weather, you need to keep on-top of the bottle temps
make sure it's a constant 900-950psi, no matter the outside temps
either warm it up to raise the bottle pressure
or cool it down to decrease the bottle pressures
you really need to start keeping a log of what the conditions are
when & where, refer back to them for tuning
