NHRA Altitude Correction Factors

[Daytona]

NHRA ALTITUDE CORRECTION FACTORS
Stock & Super Stock
1st ET/MPH factors = Convert to Sea Level | 2nd ET/MPH = Convert to Altitude
Track Name ~ Altitude ~ ~ ET / MPH ~ ~ ET / MPH
DIVISION 4
Amarillo, TX ~ 3700 ~ ~ .9549 / 1.0479 ~ ~ 1.0472 / .9543
Roswell, NM ~ 3700 ~ ~ .9549 / 1.0479 ~ ~ 1.0472 / .9543

DIVISION 5
Denver, CO ~ 5800 ~ ~ .9276 / 1.0773 ~ ~ 1.0781 / .9282
Douglas, WY ~ 4900 ~ ~ .9393 / 1.0647 ~ ~ 1.0646 / .9392
Grand Junction, CO ~ 4800 ~ ~ .9406 / 1.0633 ~ ~ 1.0632 / .9405
Great Bend, KS ~ 1900 ~ ~ .9783 / 1.0227 ~ ~ 1.0222 / .9778
Julesburg, CO ~ 3500 ~ ~ .9575 / 1.0451 ~ ~ 1.0444 / .9568
Pueblo, CO ~ 4900 ~ ~ .9393 / 1.0647 ~ ~ 1.0646 / .9392

DIVISION 6
Anaconda, MT ~ 5100 ~ ~ .9367 / 1.0675 ~ ~ 1.0676 / .9368
Ashcroft, CAN ~ 1700 ~ ~ .9809 / 1.0199 ~ ~ 1.0195 / .9805
Boise, ID ~ 2700 ~ ~ .9679 / 1.0339 ~ ~ 1.0332 / .9672
Calgary, CAN ~ 3500 ~ ~ .9575 / 1.0451 ~ ~ 1.0444 / .9568
Lewistown, MT ~ 4100 ~ ~ .9497 / 1.0535 ~ ~ 1.0530 / .9492
Medic.Hat, CAN ~ 2300 ~ ~ .9731 / 1.0283 ~ ~ 1.0276 / .9725
Saskatoon, CAN ~ 1600 ~ ~ .9822 / 1.0185 ~ ~ 1.0181 / .9818

DIVISION 7
Fallon, NV ~ 4000 ~ ~ .9510 / 1.0521 ~ ~ 1.0515 / .9505
Inyokern, CA ~ 2400 ~ ~ .9718 / 1.0297 ~ ~ 1.0290 / .9712
Las Vegas, NV ~ 2100 ~ ~ .9757 / 1.0255 ~ ~ 1.0249 / .9751
Palmdale, CA ~ 2700 ~ ~ .9679 / 1.0339 ~ ~ 1.0332 / .9672
Salt Lake, UT ~ 4400 ~ ~ .9458 / 1.0577 ~ ~ 1.0573 / .9454
Tucson, AZ ~ 3000 ~ ~ .9640 / 1.0381 ~ ~ 1.0373 / .9633

[kwhauck]

daytona, you may want to note somewhere that supercharged and turboed cars are half factor for altitude correction....

[Daytona]

I believe there is an indicator about that somewhere in NHRA's tech data. I just have to find it and post it. But, yeah, the numbers above are only for normally aspirated (carburators or FI) cars.

[kwhauck]

well on this page it says NOTE: Supercharged and/or turbocharged cars (i.e.: AA/A, AA/AT, BB/A, BB/AT, A/PM and AA/PM) use half factor; TA/D and TA/FC cars are not factored. look between the two tables....if that is the info you are lookin for.....

[Daytona]

Yeah, that's partly it but there's some more specific data aorund the charges and turbos. The note you reference in the link really pertains to Comp, S/C, S/G, S/ST classes more than it does to Stock Eliminator (which is closest to our set-ups).

For now, you can half the data and that should still give you adequate reference formulations.

[MikeSS]

Thats awesome. Unfortunately, the two tracks here in Southern Ontario are not NHRA and are not on the list.

Maybe there is an IHRA list similar since the track I always run at has IHRA events.

[Daytona]

As long as you know the altitude of your local track(s) you should be able to find a track on the NHRA list that's close enough in similar altitude to make some good assumptions. If you don't know what the altitiude is you can always call the track's office and they should be able to tell you relatively quickly.

[AleroB888]

Originally Posted by kwhauck

daytona, you may want to note somewhere that supercharged and turboed cars are half factor for altitude correction....

I have reached the conclusion the NHRA is assuming that the boosted cars will be retuned when changing tracks, meaning that the owner will "turn up" the boost for a high altitude track, or decrease boost when going to lower altitudes.

On both occasions when I have kept the same tune and boost level, and ran in Denver and Kentucky at about the same temperatures, the difference has been about one full second, or a factor of about 0.93. That is almost exactly what NHRA says is the N/A factor.

[kwhauck]

what about humidity factors greg, denver is a lot drier than kentucky

[AleroB888]

Originally Posted by kwhauck

daytona, you may want to note somewhere that supercharged and turboed cars are half factor for altitude correction....

Originally Posted by AleroB888

I have reached the conclusion the NHRA is assuming that the boosted cars will be retuned when changing tracks, meaning that the owner will "turn up" the boost for a high altitude track, or decrease boost when going to lower altitudes.

On both occasions when I have kept the same tune and boost level, and ran in Denver and Kentucky at about the same temperatures, the difference has been about one full second, or a factor of about 0.93. That is almost exactly what NHRA says is the N/A factor.

Originally Posted by kwhauck

what about humidity factors greg, denver is a lot drier than kentucky

That's a less important variable, since there are times of the year in Kentucky that are fairly dry, and some times in Denver that are humid. In either place, if you have storms moving in, all bets are off, the barometric pressure can change, too.

It seems logical to me that there exists some optimum amount of humidity for performance. Not enough could increase heat, possibly leading to detonation, or too much could displace intake air, causing power loss..(what about water injection?)

But other things equal, in the E.T. range most of our cars run, you will gain about a second going to sea level from Denver, boosted or not, if you change nothing on the car.