I need some advice and opinions about what's going on here. This is what's happening During qualifying (daylight hours) the car runs consistent, look at the timeslips, every pass (3) in qualifying was in the 6.08's, the first slip is the first elim round, pretty close to dial in so I felt good about buying back in and did so. It was the second pass(an hour after the sun went down) the car broke out, and not just by a little, over 2/100ths from the first pass. Track conditions havn't changed other than cooling a bit and air temps have dropped maybe 5 degrees. Now I know the time difference doesn't seem like much but it's huge in bracket racing. The only time the car went into the later rounds(5th) we started with 6.08 dial and chased it to a 6.00 with a 4. To have to chase a car as much as a full tenth as the evening goes on is crazy to me. It's as if the car becomes demon possesed after the sun goes down. Maybe some of you guys that race under high heat and humidity conditions can clue me in as to what's going on here. I'm thinkin of jetting the carb down a size?
Based on extrapolating the NHRA density altitude correction factor and assuming it applies the same for a 1/8 mile, to go from a 6.089 to a 6.064, the altitude density would have to change by about 1900'. If you know the change in air temperature, air pressure and dew point you can easily calculate the change in density altitude. I think they have weather measuring instruments to help racers figure out what the difference might be. Sounds like your having a great time. Good luck.
Thx Eric...so I guess the question would be...What kind of change would there have to be in those weather factors to have that big of a change in the altitude density? Typically the most drastic change would be in the humidity level increasing by some 15-20 percentage points after the sun goes down, then level off and the air temp continue to drop slowly. An increase in relative humidity from 60-80% and a decrease in air temp from 90-82 could cause the car to run as much as a tenth faster as the night progresses?!! Hmmm...I may need to buy an humidistat
Well, if you're around bracket racing....and any particular track, you'll find out what your car does. Mine is similar. Rounds 1-3 (qual rounds) it will run withing thousandths. first round of elim it will always run .03 slower, and stay there the rest of the day. Today for example...8.010, 8.012, 8.011 in qual, first round of elim, 8.04...and stayed there for the rest of the day, except one time where some leaves fell off of an old gum tree and parked themselves at the 330'...which is where I got a little sideways and ran a 8.09. Patience is the only way you'll find out what works and what doesn't. Every car and race track is different. The local track here....one round might be perfect, next there might be a little moisture in the right lane, next round there might be absolutely nothing wrong...but it will run slower and/or get out of shape in one lane or the other. Just how the track works....and once you figure it out, you'll know what to dial. Been like that for 20+ years, and I don't see it changing any time soon. I have tried everything from calc'ing DA, track surface temps...basically the scientific way, and it will always throw you a curve eventually. Usually in the final round!
i use a tag weather station, but it's only as good as the info you put into it. also i keep a log book of every run. then i throw it all out the window and guess. as far as changing jets. i try not to do anything at the track, if i don't have to. i just bring a lot of shoe polish.
the bigger the badder the motor.....the more "good & bad" air will effect performance. I have chased mine around a .10 at our local track on certain nights. A towel on the window is worth .03 in the bag
Rick, it's the aliens man........they've been watching all this time;:16suspect waiting- but now they've gone too far........messing with a Maverick. Have you aliens no shame?!?! No actually I don't have a clue other than the fact that your motor is built up so much that even a slight change in the weather can be felt/shown in it's performance. Even my puny little motor knows the difference in good weather and bad. It let's me know every day! Good Luck and HAVE FUN!!! Preston
Some good info from everyone....even Preston, if I do everything right and still breakout I can always blame it on the aliens. Seriously though I'm gonna start logging times and changing weather conditions. the only thing I can see at this point is the drastic change in the humidity. This could just be my inexperience and lack of patience.
A couple of years ago, I kept a data log of as many variables as practical each run (admittingly guessing at some of the variables). The more emperical data I had, the closer I would come to actually dialing it in close. I don't think your varyng that much (IMO). Here's a great little site for dial-in strategies for bracket racing - http://www.asmartin.com/b_dial.htm
Man. After I read both viewpoints on the effecst of humidity, I got a headache. I do not have any scientific data to back it up, but I'd say humidity IS a huge factor. When you get it all figured out, write us a tech article. Good luck and keep having fun.
Check this page out: http://www.jbsdragracing.com/Draglog.html Check these message boards here to ask questions: http://jbsdragracing.com/ http://www.perfectrun.com/
Looks like some good software...only problem is I'd have to have a laptop to use it. Rick something is a huge factor, to run 3-6.08's in a row and breakout with a 6.06...if I could have anticipated that much difference on that run and every subsequent run I would have chased it to a 6.00 like the week before last. I know it's not much, but it's huge when these peckerwoods are running dead on, I gotta get this thing figured out. What's gonna be great now is my tranny and converter go back in it at the end of the week...it will be like starting all over again.
I honestly believe that unless you stage the same every time (like 'bumping' into the final staging bulb by +/- 1"), and leave at the same rpm everytime, you could easily be off by (.02 ) (again, just my humble o) Good luck on the 'new' combo (consistancy and performance-wise)
