demonspeed

iTrader: (7)

This is probably about as dumb as my "what is race weight" question, but I honestly have no clue what you guys are talking about when your saying "DA at 400+" or something. Help me out!

Race Car Driver

DA refers to density altitude, which is the primary factor controlling the power made by internal combustion engines. Generally, horse power is inversely related to DA, e.g., the lower the DA, the higher the HP and torque.

The formula uses air temp, barometer, altitude and dew point.

demonspeed

iTrader: (7)

So it's not something printed on the timeslip then...

Race Car Driver

no, but air temp and barometric pressure might be.

demonspeed

iTrader: (7)

Where I race, they don't print much of anything. So I guess I'll never know my DA

T6Rocket

http://weather.noaa.gov/weather/NC_cc_us.html

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

The first link is a weather site that you can change to any city in any state and get the exact conditions for the last 24 hrs. So you can go racing, then look on the site afterwards to see exacty what it was.

The second link is the density altitude calulator - that you take the above numbers and punch in. You will have to know the elevation of the track though. Have fun!

Al

demonspeed

iTrader: (7)

Wow, thanks a lot! I'll remember that for next season.

1ScrudeDude

I can tell ya one thing, DA here in S. FL. must suck, esp. in the summer.

ONGRNGO

So what is a good DA then?

Dan

Villain281H

iTrader: (5)

a good DA is under 500 ft+ or negative (usually found in the winter or Texas)

Scrude,

even up here in Gainesville it gets to 3000 + DA during summertime!

Derek

Elite_Hot_Rod

Sea level at 59 degrees C is ideal.

WicketMike

iTrader: (13)

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

http://www.modulardepot.com/density.php

http://www.weatherunderground.com/ here you can type in the city and choose the date and it has the weather from that day by the hour.

BTL FED

iTrader: (9)

Thats why I got one of these little gadgets =0)
http://www.computechracing.com/drsystem.html
I have the 3000 and it works great

BKHAWK1

Take it from the ole helo pilot;

A Standard day at sea level = 29.92in of mercury at 15deg C.

Pressure alt is figured from using the standard day at sea level. DA= Density altitude is defined as pressure altitude corrected for temperature deviations from the standard atmosphere.

now to put that into english. the less dense(500+or- on the da) the air, the least amount that your cars engine has to work at pulling in enough air volume into each cylcinder to get that idea 15:1 air fuel ratio. when the air is more dense(+3000 da like it gets here in the south on a hot summer day) the harder your engine has to work at pulling in that air volume to get the ideal air fuel ratio to make power.

low DA= air molecules close together
high DA= air molecules far apart

maybe this will be as clear as mud?

Kevin

BADSZ28

iTrader: (39)

How do you determine the altitude of the track once you have all the other data? Is there a site that tells you the altitude of tracks in the US or do we need to call up the track and ask?

ACW

If there is a site out there, I didn't find it in a quick search... I don't know if the people who run the track would necessarily know its altitude either. My suggestion would be to find a friend who has a GPS device, and get an altitude reading from that at the track

BADSZ28

iTrader: (39)

Not a bad idea.
I found that some city websites indicate there altitude.

Tom the roofer

iTrader: (9)

Try this

http://chasinracin.com/track-locator/bytype.shtml

WJ SOM SS

iTrader: (11)

Most reputable tracks know and post their altitudes on their websites, in newsletters, etc.---especially if they're a IHRA or NHRA sanctioned track. The sites the previous guys have posted up are great info points as well. WJ

BKHAWK1

if you call this # 1-877-269-2967; it will get you the nearest airport around that has automated weather reporting. It will give you wind direction and speed, Pressure alt, DA and a few other things. that number is good anywhere in the world. THis might help some of you who have an airport near the track.