TORCHD 02 TA

iTrader: (39)

I have been reading a lot, and people are always askign what was the DA. So what does the DA have to with how we run?

Also from what i gathered, the required info to figure DA is: Temp, Pressure, Dew Point and Altitude....

So where can i find all this info at? And what does it all mean?

TORCHD 02 TA

iTrader: (39)

Ok so i jsut foudn the best DA calc in the world. Seriously. It has every track in the US. And it gives you all the info you need and plugs it in for you.

My question is what is DA? it told me that the track i was at yesterday was at a DA of 2069 ft... Here are the other readings: air temp was 77*, Barometric Pressure was 33.03 and RFelative Humidty was 54%. That gave me the Density Altitude: 2069 feet and Relative Density: 94.08 %

So again what does this all mean?

ads_99ta

basically air gets thinner as the altitude rises, so there is less air for the car to breathe as the altitude goes up which explains why cars run so much slower in the higher altitudes. even a track at 700 ft above sea level can see a DA that is 1500 or more. which means the air is about what it would be at 1500 ft.

TORCHD 02 TA

iTrader: (39)

How can that be? What affects that? So again the term DA means what? if the track lets say is at 700' above sea level then the DA means that at the time of day (temp, barometer and dew point) can make it feel like the air is from 1500' above?

Feel bad for the guys in CO then

old_goat

I guess in a nutshell, it's how much 'air' you have to push away from your car to get a good time in the quarter mile.

The higher the DA number, the worse it is for racing.

Take for example a bucket. Fill the bucket with those packing peanuts and see how hard you have to work to get your hand to the bottom of the bucket. Very little.

Now, take and fill a bucket with BB's and see how hard it is to get your hand to the bottom for the bucket. A whole lot.

The bucket with packing peanuts would be like negative DA, or the best you can get, while the bucket filled with BB's is like positive and high DA, terrible conditions.

I can't speak for the northern US, but down here in Texas, there is only a couple of months were we can race with good weather (DA).

http://www.dragtimes.com/da-density-...t+Weather+Data

Plug in (if it doesn't do it already) 8-17-2008 @5:53 pm. The temp is 90 barometric pressure is 29.93 and the humidity is 59%. I am using Houston Raceway Park at 38 feet above sea level as a baseline. The DA is a terrible 2366. Now plug in 13.0 @110 for a time and mph. Your 'corrected' time is 12.639 @ 113.215 MPH, which indicates that the weather is costing you about .37 second and 3.21 mpg.

Now plug in 12/22/2008 at 2:53 pm. Your temp is 39.9 degrees, humidity is 38% and pressure is 30.39, which gives you a great negative DA of -1737. Due to the air, it is so easy to get your 13.0 @ 110, that your corrected time is now 13.255 @ 107.754 MPH. Of course on a night like this, you don't even consider corrected time.

http://www.dragtimes.com/da-density-...time=2:53%20PM

TORCHD 02 TA

iTrader: (39)

Thanks for the info. And i found that same drag link searching on google to figure this all out. I like that link, gives you all the tracks

Question why is the time worse at your 12/22/2008 example with the corrected time? wouldn't the time be better as the DA would be more in the negatives?

chrs1313

iTrader: (24)

Nope it corrects it to zero DA or the SAE conditions per say…that is why I compared it to dyno numbers and SAE vs. what it ran or did that day…so if you run in any +da day your times will be faster when you correct them…if you run in any – da if you correct your times you will be slower…but the DA is just used to show how much extra hp you have due to air…

So for my car roughly 1000ft is 10rwhp, 1mph…so if I race is 1500ft DA and the car runs 121mph if I were to run in 500ft the car will mph 122…so if you want to compare how much a mod helped someone else or even yourself compared the da conditions and subtract or add rwhp as needed…so using the example above if I added a mod to my car since I ran the 121mph in 1500 ft DA and I mphed 123mph in 500ft the mod was worth around 1mph and the other 1mph was due to the better DA conditions

121mph is 1500ft

123mph is 500ft added a mod…1mph for mod…1mph for DA…

But remember when you correct your numbers jonas that is too 0 DA…in the Fall we should see DA’s around -700 to -1000ft

and where is my video haha

Duffster

iTrader: (103)

it's based on the weight of the air. . . . for instance at sea level it's 14.7 pounds per square inch (hopefully this sounds familiar so far). If you have a piece of paper at sea level and draw a 1" by 1" square and imagine a column straight up to the edge of the atmosphere, the air in the 1" by 1" by 60 mile (or so) column captured would weight 14.7 pounds.

Now, if you go up 2000' and do the same square to the top of the atmosphere, it might weigh in about 14.63 pounds and probably different humidity and temperature. All this combines to say less air getting into the car and less air means less power.

DA is calculated to guesstimate how it would do in IDEAL conditions or say what your car COULD be capable of.

Good?

slobird

iTrader: (1)

The altitude at our track is 3700 ft above sea level and our density altitude is usually over 5000 ft, would love to run in Houston some day! To get to decent air we have to drive over 300 miles!

old_goat

Houston is not a good place to run between April and October. It is very hot here with high humidity. We don't have 5000 DA, but we sure get some 2000's.

REDGAR

yeah it is tough to have to compare our times with others who don't have the same air and the calculators are just that, calculators.

Just a note on the dragtimes info, it is not weather from the tracks so tracks DA can be very different. For instance, I rant at E'twon last week and my TAG weather stattion was reading 1800' above around noon. Using the dragtimes site it reads about 500 or 800 I forget which it was for the time closest to noon.

The point is, if you are going to compare DA your source is important too.

AChotrod

iTrader: (17)

dragtimes calculator is the DA from the closest airport, so Its Not 100%. Couple weeks ago I ran at KCIR the track is 800ft and the DA was 3500+ at times but DTs site says only 3200

sd2001ta

iTrader: (2)

so the closed the da is to zero or in the negitive the better the car will run?

DADDY&GIRL93TA

Yes. the lower the DA the better the car should run