Quote:
Originally Posted by Redlight
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http://www.wallaceracing.com/convert-et-to-msa.php
Maybe I'm doing it wrong, but I input 1st run of 9.40 @ 141 at 300' elevation, 70°, 45%, and a 2nd run of 2500' elevation, 80°, 45%, and it predicted I would run 9.29 @ 142.72!!!
I created a spreadsheet to do Density Altitude calculations (I'm too cheap to buy a real weather station that does it for me). It is a combination of stuff I found in textbooks and the internet, with an additional factor added to make it match NHRA's value (when they post Density Altitude on their racing results pages). Here is the cell formula:
=(44.3308-11.1802*((D3*3386.389/((((D1-32)*5/9)+273.15)/(1-0.378*((6.1078*10^((7.5*((D1-32)*5/9))/(237.3+((D1-32)*5/9))))*(D2/100)/(D3*33.8693)))))^(0.234969)))*3280.8333+(550+((44. 3308-11.1802*((D3*3386.389/((((D1-32)*5/9)+273.15)/(1-0.378*((6.1078*10^((7.5*((D1-32)*5/9))/(237.3+((D1-32)*5/9))))*(D2/100)/(D3*33.8693)))))^(0.234969)))*17))
D1 = temp °F, D2 = humidity as whole #, D3 = barometric pressure in-hg
It's not perfect, but it comes pretty close to NHRA's and the other commercial weather stations. I use it with a cheapo electronic weather station that has temp, humidity and pressure.
Regards,
Michael Pliska