Last Call

iTrader: (4)

I here everyone talk about temperature, elevation, humidity, barometric pressure, and DA.

I know ideally, a cooler temperature is better for times, to a certain extent based on traction. In higher elevation you run slower obviously.

BUT, more humidity probably makes you run slower?? DA - I have no clue what that means.

Does anyone want to explain the optimum running conditions in terms of the above? I want to make sure I go to the track in good weather conditions.

v8

iTrader: (10)

DA stands for density altitude

when you put humidity into a DA calculator the elevation never changes, the dew point is the killer. here are the three that you can use, DA calc.,weather,NHRA factors.
http://www.csgnetwork.com/dadtcalc.html
http://www.smokemup.com/auto_math/nh...on_factors.php
http://www.weatherunderground.com/hi...lyHistory.html

FlyingLow

PA=Pressure Altitude
DA=Density Altitude

DA is PA corrected for temp and humidity. Colder dryer air gives you more power available. So the colder/dryer it is the better for your engine.

VicRed

I think i get it. But lets say a track in Colorado has a DA of 400ft, and a track in Florida also has a DA of 400ft. Even though the physical altitude is different, a given car "Should" run the same times at both tracks? Am I correct here? or way off.

FlyingLow

No, DA is not a physical height. The altitude itself is higher in Colorado. Think of DA as how dense the air is at the altitude you are. Plus the temp could be different. DA is a combo of PA/Temp/Humidity. When I'm flying and I want to know the DA I dial in 2992 in my altimeter. Then I compare that to my actual altitude. I then take that number and adjust it for the current temp and humidity.

Originally developed from formulas used by aircraft pilots to calculate lift, this relative performance altitude when calculated for racing includes additional compensation for the effects of humidity on engine performance.

tarinitup

iTrader: (11)

I liked the link to the NHRA conversion table. Accoding to the table my 14.48 would be a 13.98 @ 98.6 mph at my 2881 elevation.

VicRed

Thanks Flyinglow.

FlyingLow

Cool Over on the SRT forum this is one of the big things the guys in higher elevations complain about. I would brag about my 12.7 and they would fire back that it would only be low 13's out where they are.

Smoke

F8L Z71

Its all about DA.

I'm at about 50ft. above sea level yet on a hot summer day the DA can jump to over 3000' so on a really great day in Denver or New Mexico they can actually be "effectively" closer to sea level than I am in regards to oxygen content.

kkd60

add also, turbos, nitrous, and supercharged engines are not affected as badly by these factors.