RUQWIKR

iTrader: (11)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RAGEman:
<strong>And also, what was the DA for Little River Academy, TX @ 8 p.m on Saturday, March 9th, 2002?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Using Weather Underground for Austin: At 8 pm (7:53 pm): 51.8F temp, 15.8F dewpoint, 30.51 baro (23.6% RH calculated), 15.0 mph winds, using PAIN's DA calculator results in -1,371 feet...darn good air with favorable winds.

That said, you may lose some next time out if the air is not as tasty, but it's not like your car is suddenly going to slow to 12.0's. Take care.

Bad Habit Bird

iTrader: (12)

Wooooooo -1,371 feet. Damn you cant get much better than that. I guess me and Alan just got lucky with some of the best weather of the season. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

RAGEman

iTrader: (4)

I'm not seeing a field for dewpoint in PaiN's calculator, only for humidity. wunderground.com doesn't show the humidity.

RUQWIKR

iTrader: (11)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RAGEman:
<strong>I'm not seeing a field for dewpoint in PaiN's calculator, only for humidity. wunderground.com doesn't show the humidity.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Found Temple: For 7:35 pm it was -1832 feet DA, for 8:35 pm it was -2018: For 7:35 pm, it was 46.4 F, 12.2 F dewpoint, 30.54 baro, 24.7% RH calculated, and for 8:35 pm it was 44.6 F, 15.8 F dewpoint, 30.57 baro, 30.9% RH calculated.

BTW, I log all my runs with details on all weather parameters, etc., and slowly develop my own correction factors for the various tracks I run on just for my own info and predictions. For RH from air temp and the dewpoint you need the calculated saturated (ES) and actual vapor pressures (E) in millibars, then RH = E/ES*100, where ES and E use the temperature in celcius of the air temp and dewpoint, respectively in the following:

=6.112*(POWER(10,((7.5*temp)/(237.7+temp)))) or in other words, =6.112*(10**((7.5*temp)/(237.7+temp))).

So, 44.6 F = 7 C, 15.8 F = -9 C. In the above, they'd equal 10.0169 and 3.0977 with RH = 3.0977 / 10.0169 = 30.92% RH.

Whew! Just set yourself up a little spreadsheet in Excel or whatever to change F to C and then airtemp and dewpoint over to their associated vapor pressures. Our lesson of the day is over now.

Finally, I am not a disbeliever, just one that understands the huge impact good air has on our performance assuming nothing else has changed on the setup, etc. That's why I don't get too excited over my mph vs. what my 60's and ET's are doing. Last year, when I was in the low 12's, I had a super-duper air day and picked up around 2 tenths and 2 mph or so from the week prior with no changes only to see the gains dissappear the next week as the air conditions changed back to "normal".

<small>[ March 13, 2002, 02:54 PM: Message edited by: RUQWIKR ]</small>

BLU-BY-U

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RUQWIKR:
<strong>

Whew! Just set yourself up a little spreadsheet in Excel or whatever to change F to C and then airtemp and dewpoint over to their associated vapor pressures. Our lesson of the day is over now.

Finally, I am not a disbeliever, just one that understands the huge impact good air has on our performance assuming nothing else has changed on the setup, etc. That's why I don't get too excited over my mph vs. what my 60's and ET's are doing. Last year, when I was in the low 12's, I had a super-duper air day and picked up around 2 tenths and 2 mph or so from the week prior with no changes only to see the gains dissappear the next week as the air conditions changed back to "normal".</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">RUQ, ONYX provided this link to a calculator. It's coming up with slightly different calcs than you did, but it's in the ballpark!

http://rshelq.home.sprynet.com/calc_da.htm

RAGEman

iTrader: (4)

Yeah, I just used Onyx's calculator and got -700 ft. and it also turned up 24.7% relative humidity.

Is the barometer reading the same as the "altimeter setting"?

RUQWIKR, I honestly don't want to have to go through all that trouble to find the DA. What other factors besides DA need to be considered? Wind, I suppose. Is there anything else?

EDIT: My 11.568 @ 121.13 was made @ 7:37 p.m., so let's use the 19:35 reading on wunderground.com.

<small>[ March 13, 2002, 03:50 PM: Message edited by: RAGEman ]</small>

RUQWIKR

iTrader: (11)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RAGEman:
<strong>Yeah, I just used Onyx's calculator and got -700 ft. and it also turned up 24.7% relative humidity.

Is the barometer reading the same as the "altimeter setting"?

RUQWIKR, I honestly don't want to have to go through all that trouble to find the DA. What other factors besides DA need to be considered? Wind, I suppose. Is there anything else?

EDIT: My 11.568 @ 121.13 was made @ 7:37 p.m., so let's use the 19:35 reading on wunderground.com.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">RAGEman, normally it's alot easier to find DA as weather.com, etc. has the humidity. I take a weather radio ($20-$30 at Radio Shack) to the track and get the info by the hour, though, it's not as accurate as a portable weather station directly taken to the track. Additionally, I also get each track's altitude as well and ask the track owner if they know the % grade of the track...most don't but some do. I believe the NHRA/IHRA spec calls for max of 1% grade +/-, someone correct me if different. Some tracks are quite flat, especially through the traps, others grade up or down.

Wind doesn't make near as much of an impact as the rest of the weather conditions for cars at our speeds. They'll give you some benefit or loss, but give me a cranking low DA with a bit of a headwind vs. crappy air with a bit of a tailwind. Obviously, as mph rises, the wind will affect you more and more. Nevertheless, that's why we all hope our day at the track has awesome air...that's why we race...to go quick and fast.

I also race a low-to-mid 11-second Turbo Regal that runs mid 120's (basically stock suspension, small slicks, poor 60's) that is MUCH more finicky with changes in weather due to it being turbo/intercooled. The more data you keep, the better. I use a Tech 2 to track each run on my Formula and a laptop on my Regal. The data I can get on my Formula is a much, much more in depth than the older cars like my Regal (87). I also use on occasion a pair of wide-band 02's to monitor.

I have never had the Formula on a dyno yet as I don't care what it puts down except at the track. I'll use my buddy's chassis dyno later this spring when I do heads and cam in order to make some calibration changes via data derived from wide-bands & Tech 2 data logging. My recommendation that would be echoed by many is get a good scan tool like a Tech 2, AutoTap, etc. to monitor / record. Keep close records of track conditions, mods, weather, shift points, blah, blah, blah, weight. That way, you can prove more so to yourself what the issue is if you improve or not weekend to weekend. With two small boys, I only get out once in a while, so, I have to make the most of my track trips for testing / confirmation to my tweaking.

Most track timers seem to be consistent (usually), but may be high or low mph/ET. At "fast" or "slow" tracks, I use the data to just get an idea of tweaks / changes I made from baselines, but if things seem out of the ordinary, you'll know it and can discuss it as such. When I finally get my car out, hopefully in April, after it warms up a bit up here and the tracks open, you bet I'll be looking closely as usual at weather conditions before burning my "get out of jail free" card from the wifey for the day.

Take care and good luck to all on your goals.

PaiN

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RAGEman:
<strong>Tums,

Just out of curiosity, can you figure the DA for HRP (Baytown, TX) on Saturday, February 9th, 2002 @ around 11 a.m.? That's when I trapped 119.04 on a slipping clutch.

</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">6:00am DA approximately -1,450ft
8:00am DA approximately -16ft
2:00pm DA approximately 900ft

BLU-BY-U

cool, I love these weather threads <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

I think this type info explains some things to me. I trapped like 114 in my Z06 last week. The DA correction calced like +500ft. I also saw Mikcey's post about his incredible times he ran in his Z06 up in the northeast (ATCO I think??). Now mind you, he ran consistent 116+ with some 117's.

So, it seems that around 2000ft difference in DA can make upwards of 3 mph trap difference.

Unfortunately, I think those 30.50 baramoter type days are over for Houston this spring. It's already getting quite warm down here and I'd bet the blue northers with the big, Canadian highs are over until next fall <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

FUG!