What is D.A.?

Alright, I've been seeing a lot of people talk about D.A. Mostly on the vette forums, but it seems to be related to where the track is at. Is it altitude? I wouldn't think so, because some people were saying that a 1500 DA was good I think? I thought 1500 ft was high. So whats the deal, what is DA?

1500 sux. Basically the lower the DA the more HP you make.

Here is a site to figure out your DA.
The only requirements is you have to know your elevation of your track and current barometric pressure, dew point and current temperature.
DA Calculation (http://wahiduddin.net/calc/calc_da.htm)

It's not un-common for the people in the south like Houston, Lousiana and other low level tracks to see the DA in the -1000 range. That's giving them free HP.

Density altitude is a calculation from the elevation, barometric pressure, temperature and humidity. The DA is a theoretical altitude that the air would be like at standard conditions.

Temperature and barometric pressure will change the DA the most. Racers and pilots use the DA to estimate the amount of available HP and engine will produce. The higher the DA, the lower the HP available. An engine that dynos 500 hp is calculated at sea level. That same engine running in Denver may only produce 450 hp because of the 5000 foot elevation. Add in a hot muggy summer day when the barometric pressure is low and there may only be 400 hp available because the DA is over 8000 feet.

My local track elevation is around 3300 feet. During a typical race day the DA is usually over 5000 feet. It sure is nice to go to a lower elevation track just to see how quick the car really is. It even sounds better. For me racing at 1500 feet DA would be extremly good!

Density altitude is pressure altitude corrected for nonstandard temperatures.

Basicly what Stephen said.

When i calculate pa and da for flying it is pretty simple. Just take your current altimeter setting, you can find a airport near by and call in to the asos or awos and the recording will give you a bunch of stuff and an altimiter setting say, 29.98. The standard is 29.92. Subtract the two and mutliply that by one thousand. So 600' and the number 29.98 is above 29.92 so you subrtact. Over subtract, below add. So the Pressure Altitude is Minus 600' from your standard elevation.

Now if you want to get into Density Alititude, that is pa adjusted for nonstandard temps. Standard temp is 15* celcius. I don't know what the actual conversion is and just got done looking it over but just remember if temp is above 15* and as it increases the density altitude will be higher than PA. If it is below the da will be lower than PA. As da increases, air density decreases causing a loss of performance and visa versa. I calculate this using an E6b flight computer but i wish i knew the actual conversion.

Hopefully i kind of explained this alright. So if you really want to find your PA and DA i can help you get the phone number to a local weather data machine.

This stuff gets real confusing sometimes ;)

We were getting negative DA's all weekend for the Thunder Shootout. Nice weather, high barometer and BELOW sea level really does wonders for a car. :)

EDIT -- Double post. :(