Originally posted by V8BRICK
I'm gonna argue these correction factors. True NRHA is the authority, but those numbers aren't on turbo-charged cars.
Here's and excerpt from a site that makes sense of determining the handicap of altitude and turbo engines. Doesn't take into account the lag time when you have no boost, but it's closer than the NHRA's fantasy corrections:
"CORRECTING FOR ALTITUDE
If we were dealing with non-turbo cars, this would be easy and we'd publish a formula. But with pressurized cars, the correction factor for altitude depends on the boost you run.
For instance, Sea Level air pressure is 14.7 psi. If you go to a track in Boise, Idaho (2850 feet above sea level) the air pressure is now around 13.25 psi. That's 90.1% of sea level pressure. If the temperature doesn't change and you have an normally aspirated car, your power output will now be 90.1% of what it used to be, so I'd tell you to correct by multiplying your calculated HP by an extra 10.9% (1/.901, or 1.109).
However, (and this is the beauty of turbo cars!!) Let's say you were running 10 psi of boost in the first place. So at sea level, your car was really getting 24.7 psi (14.7 + 10). Now you leave the wastegate at 10 psi and race at Boise. Your manifold pressure is now 23.25 psi (13.25 + 10). Note that YOUR power isn't down as much.. it's down to 94.1% of what it is at sea level. So you should correct with an extra 6.2% (1/.941, or 1.062).
If you wish to calculate your own correction factor, here is a handy table of elevation (feet above sea level) vs. standard day atmospheric pressure (psi):
http://www-unix.oit.umass.edu/~tcroy...dollardyno.htm
0 14.70
500 14.43
1000 14.18
1500 13.92
2000 13.67
2500 13.42
3000 13.17
3500 12.92
4000 12.69
4500 12.45
5000 12.23
5500 12.00
6000 11.78
6500 11.56
7000 11.34
7500 11.13
8000 10.91
8500 10.71
9000 10.51
9500 10.30
10000 10.11 "
So depending on boost levels, this is the way I'd calculate my corrections.
Fuck... I've been thinking of a way to refute that for the past 20 minutes but haven't come up with anything yet...
Anyone?