Fikse

Select the track, date, time, and this DA calculator will lookup the weather, elevation and output the DA....

http://www.dragtimes.com/da-density-...calculator.php


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DFW01E55

Good stuff, thanks Fikse.

Edit:
I don't know how accurate this is, but here's the other side of the equation:
Correction factors

I like it because it "corrects" my best run in my CL55 from 12.06 at 115.8 to 11.7 at 119.2.

MB_Forever

Great, I can't wait for the approximated corrections.....

Fikse, it'd be even nicer if after selecting the track and hitting the "Get Weather Data" button, it displayed the hourly DA in an additional column.

MHP

Guys, check out www.smokemup.com it's the NHRA's official website for DA correction.

juicee63

Thats what I use.

But I love the fact dragtimes has added a DA calc!!!!

WAY TO GO FIKSE, you win

Fikse

Here are some more correction factor tables breaking it down stock na, modified na and FI cars...

http://www.wallaceracing.com/altitudecorrection.htm

anyone know the formula used to produce these tables, or figure it out?

juicee63

From months of looking the information , "equations" are the property of SAE, and can be purchased. They are derivatives and all the correction tables are based on known air pressure's at specific altitudes.

The NHRA factors are simple density ratios, with sea level being zero (standard). The DA calculation is more accurate than the altitude correction because humidity and temperature are part of the equation. I think you can find all the equations here

http://wahiduddin.net/calc/density_altitude.htm



Say you run 12 seconds at 115 at standard SAE condition which is standard air pressure.

Each track over 1600 feet has a factor although 100 feet will have an effect on your run. NHRA only allows correction for tracks at a physical altitude of 1600 feet or more. This was 1200 feet but was changed in 2007.

Now lets take your exact same set up(car) and run her at 3500 feet. They simply do a ratio of what the column of air at 3500 feet pressure is vs. standard(0 feet) sea level pressure vs 3500 feet pressure. That becomes the ratio. Once again this is a simple air pressure calc and does not consider humidity or temp.

The DA calc is more accurate as it considers more variables but it also can be very inaccurate if the conditions are measured falsely.