anyone know of any good places on the net to get some formulas to calculate air density?

 

They're not simple formulas but go to the Calgary Drag Racing Association (link below) web site. In the tech section there's a section on weather math and how to calculate density altitude.

I have formulas calculating how to predict an ET similar to those used by commercial devices sold to racers. All the information is on the internet once you understand what to look for and how to use it. It's taken me a about a year to find all the information and figure out how to use it. I've put all my formulas in Excel and use a laptop at the race track to do all my calculations.

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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

Even some of the small calculaters can find your AA(adjusted altitude). The larger laptop programs allow you to enter traction and track conditions into the equation. you better have a pretty consitant car or chasing this information will drive you crazy.