Posted By: mopar65
??? How much does the heat mess up your 1/4 mle time?? - 07/16/12 11:45 PM
Well my friend came home from working over seas for the last year and wanted to go racing. So we loaded up my dart and went racing last Saturday night.well that nite the temp was not bad around 70-71 degrees. But the humidity was down right nasty. Oh also for got to add that we did not start racing until 12 am. It was so bad that every body was fighting to keep there windshield dry and not fog up. Well any way here are my 1/4 times. all of these were done on 93 pump gas.
11.03 at 122 mph 1.56 60 foot
11.01 at 122 1.56
10.91 at 122.5 1.55
10.98 at 121.8 1.60
11.01 at 121.0 1.60
i think i spun a little bit on most of the passes and the track was going away on the last two passes. But i am down 2 mph in the 1/8 and around 3 mph in the 1/4 from what i ran last fall which was a best of 10.68 at 125. So is it normal to loose as much as i did in the heat or is my car just slow in the heat. Thanks For your time. Mopar65
Posted By: 383man
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 12:06 AM
Two to three tenths in real hot heat and humidity is not bad compared to a nice cool 60 degree day with no humidity. I have not run my new combo much but my old combo ran a best of 11.49 in cool air and would run 11.70's in the heat. 50's and 60's on decent days. I remember on a hot June day I ran from 11.74 to 11.78. It would also drop 2 or 3 mph. If you drop alot of et on hotter days you may be to fat on the carb. Ron
Posted By: mopar65
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 12:54 AM
Thanks for the info RON. last Saturday was the first time i have been back to the track in over a year.so it was good to get back behind the seat. also when i ran the 10.68 it was some time in November and the temp was around 50-52 degrees.well i guess it was just me worrying about nothing. Thanks Mopar65
Posted By: John Brown
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 02:03 AM
Here's a calculator that will let you compare times by heat, humidity, altitude and air pressure. Look around, you can also compare times at different tracks and different days.
http://www.dragtimes.com/da-density-altitude-calculator.php
Posted By: Dago Red
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 08:24 AM
It has been my experience that pump gas does NOT like temp changes. I run a low compression small block and going to the 100 unleaded really made a difference. Even different brands of pump gas will give you fits.
Posted By: gregsdart
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 01:05 PM
As a rule of thumb, a well prepped drag car on gas will change about .01 per 200 ft DA change. My Dart on Alcohol changes much less, about .01 per 400 ft DA change.
All this depends on tuneup and traction of course. On a really hot day I expect to lose some 60 ft.
Posted By: Mr.Yuck
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 02:35 PM
Idon't have much seat time in this car but hot weather usually takes 2-3 tenths from a car. You can be more consistant if you run a cool can, but I think it will still slow down some.
Posted By: Dragula
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 03:20 PM
Well, mine went 6.58 in the cooler morning and then 6.47 in the heat last week! MPH got better too! I will let you guys figure that one out.
Temp was reading 99* in the sun, 88* in the shade. Launch rpm, shift rpm, everything pretty much the same.
The 6.58, the motor was still not fully heat soaked, and the 60ft was off thanks to the burn out. Typically its a 6.52, which is what the 2nd pass was, but we did not expect to dip all the way down to 6.47 on a hot day. The next couple of passes, the car just got faster on every pass with no changes on my end, just getting a better burn out than the 1st pass and trying to be consistent with motor launch temps. Motor is still a little tight, and the chassis might be as well. So in the heat of the day it was right around 6.49, then it cooled down a little to about 83* and we got the 6.47.. The car's record was 6.44 on a nice cool night so, not bad in the heat. We run pump gas, and i think it changes more than it really should, but we are still learning with 90 actual full passes on the car now.
Posted By: mopar65
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 03:28 PM
can you guys help me understand what the numbers mean in the DA chart i posted mean. I mean i put in 10.91 at 121.0 and it came up with a 10.50-10.60 something et. so is it saying that is what my car should of ran in the heat??? thanks for all the info. Mopar65
Posted By: gregsdart
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/17/12 04:33 PM
The Density altitude is a measure of available oxygen to use.
Humidity, temp and barometric pressure are all taken into account to arrive at the Density altitude number. So it doesn't exactly measure altitude, but a combination of the effects of all three.
I have found the Walace calculator for converting to zero altitude to be generous.
My car doesn't change as much as the category I am in.
Posted By: OUTLAWD
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/18/12 01:35 AM
Don't have DA #'s but in cool, crisp mineshaft air (Atco) I would run 2-3 tenths quicker, and 2-3 mph faster than I have been in the heat and humidity lately.
Posted By: Paul_Fancsali
Re: ??? How much does the heat mess up your 1/4 mle time?? - 07/18/12 07:17 PM
I quit using my cool cans but still have them. Ethenol in the gas was giving me fits. Regardless heat will slow you down but can also pickup if the humisity is lower and track is not slick. On cool days I go to a 195 stat to keep the heat in and have gone faster as a result with a low comp engine. High comp is another animal altogether.Keep it at 180 and you should be good
Atco or Cecil when the air is good yields great times. Went our best of 9.94 at 135 at Cecil in less than ideal conditions (hot, but dry) and 10.11 at MIR in high heat/humidity.