juicee63

Correcting timeslips for weather, altitude.

No need to jack threads when questioning why I correct everyones 1/4 mile times.

Here is why I do it
1.To put all cars on a level playing feild
2.To speculate on which cars are fastest
3.To properly calculate dial times based on temp and altitude
4.To see if modification has added or subtracted HP
5.To better understand the effects of atmospheric condition on my motor
6. To better know my potential opponet
7. To set the ultimate time and trap for my car


Two very popular FI cars from this forum(and members)and one N/A E63

Jrockets car an E55 runs a 12.429@114.637
enzom's car an E55 runs a 11.912@118.432
Bluemax car an E63 runs a 12.724@113.792

if the cars lined up , same day same track same moment,
and were driven by computer which car would be faster through the 1/4 mile?

Jrockets run was at 4100 ft
Enzoms run was at 1600 ft
Bluemax run at 4100 ft

Altitude corrections are here
http://www.nhra.com/tech_specs/altitude.html

see what you guys think.

For those not wishing to use the NHRA witchcraft just explain to me from this small bit of data rank the cars from fastest to slowest

Ted Baldwin

.......the car that actually physically ran the fastest time is the fastest, period! In this case it is the car that ran 11.9@118

..........another car on the list may have the potential to be faster. However until that car actually physically runs that time, it remains the slower car.

.........The athlete that ran the fastest 100meter dash is the fastest and gets awarded the world record. If a week later another athlete runs a slower time at a much higher altitude, the world record does not get yanked from the first guy and given to the second guy. You have to actually physically run the fastest time.

...........the student that gets the most number of quetions correct on the test wins first prize. Another student could have scored higher were it not for the bad smell in the exam room that gave him a headache. Had both students been exosed to the same fumes, perhaps the second student could have scored higher. However until the second student actually scores higher on the test, the prize remains with the first student.

Ted

juicee63

1. Enzom wins because his car ran the fastest time.

rflow306

Again incorrect, Here is the actual elevation of a track on the list Amarillo-Texas

Amarillo Dragway
Amarillo, TX

Schedule · News & Results · Points

Track Specifications
Configuration: Dragstrip
Length: 1/4 mi.
Surface: Asphalt/Concrete Pad

Sunday
E.T. Brackets
Friday
TNT
Saturday
Super Street Shooutout Series

Travel Information
National Speedway Directory Directions:
Located 7 miles south of Amarillo between Washington and Osage streets

View Map | Find Lodging
Notes:
Camping Allowed.
Track elevation 3,700 ft. TNT Fridays: 8 to midnight. Super Street Shootout Series Sat. 9 - midnight. ET Brackets on specific dates only.


Here is the nhra website one more time

NHRA ALTITUDE CORRECTION FACTORS
Comp, S/C, S/G, S/ST
Convert to Sea Level Convert to Altitude
Track Name Alt ET MPH 1/2ET 1/2MPH ET MPH 1/2ET 1/2MPH
DIVISION 4
Amarillo, TX 3700 .9646 1.0337 .9823 1.0168 1.0367 .9674 1.0180 .9834
Roswell, NM 3700 .9646 1.0337 .9823 1.0168 1.0367 .9674 1.0180 .9834

The NHRA uses actual track altitude, a constant not the DA which is more like a Ferris wheel

You are free to use any correction factor you like, just don't get mad when some members on this board don't give it any credibility. The da should only be used as data point to add to many other data points to gauge the performance of the same car under different conditions, not different cars on different tracks.

juicee63

Thanks for coming over... where do you think this table comes from? I use this EXACT table when correcting my times. It is not a ferris wheel it is based on Density Altitude which is the very table you are posting? SAE standard correction table for altitude

NHRA ALTITUDE CORRECTION FACTORS
Comp, S/C, S/G, S/ST
Convert to Sea Level Convert to Altitude
Track Name Alt ET MPH 1/2ET 1/2MPH ET MPH 1/2ET 1/2MPH
DIVISION 4
Amarillo, TX 3700 .9646 1.0337 .9823 1.0168 1.0367 .9674 1.0180 .9834
Roswell, NM 3700 .9646 1.0337 .9823 1.0168 1.0367 .

9674 1.0180 .9834


Altitude and Atmospheric pressure are accounted for in the table

The Altitude of this track is measured using a DA calculation.

Put more simply

The Density Air calculation simply takes the temperature, barometric pressure and humidity and converts it to International SEA LEVEL

To convert your timeslip ET and MPH to sea level. Multiply applicable factor times your ET or MPH.

(Example: You ran a 13.8 @ 100 MPH at 5000' elevation track. The correction factors are .9367 and 1.0661 for 5000'. (13.8 * .9367) = 12.93 , (100 * 1.0661) = 106.61 MPH. So the correct timeslip would be 12.93 @ 106.61 MPH.)


Altitude above Sea Level (Feet) Elapsed Time Factor (ET) Trap Speed Factor (MPH)
1200 .9874 1.0129
1300 .9861 1.0143
1400 .9848 1.0157
1500 .9835 1.0171
1600 .9822 1.0185
1700 .9809 1.0199
1800 .9796 1.0213
1900 .9783 1.0227
2000 .9770 1.0241
2100 .9757 1.0255
2200 .9744 1.0269
2300 .9731 1.0283
2400 .9718 1.0297
2500 .9705 1.0311
2600 .9692 1.0325
2700 .9679 1.0339
2800 .9666 1.0353
2900 .9653 1.0367
3000 .9640 1.0381
3100 .9627 1.0395
3200 .9614 1.0409
3300 .9601 1.0423
3400 .9588 1.0437
3500 .9575 1.0451
3600 .9562 1.0465
3700 .9549 1.0479
3800 .9536 1.0493
3900 .9523 1.0507
4000 .9510 1.0521
4100 .9497 1.0535
4200 .9484 1.0549
4300 .9471 1.0563
4400 .9458 1.0577
4500 .9445 1.0591
4600 .9432 1.0605
4700 .9419 1.0619
4800 .9406 1.0633
4900 .9393 1.0647
5000 .9380 1.0661
5100 .9367 1.0675
5200 .9354 1.0689
5300 .9341 1.0703
5400 .9328 1.0717
5500 .9315 1.0731

Standard Atmospheric Conditions Altitude
(feet) Pressure
(in. Hg) Temp.
(F°) Density
(%)
sealevel 29.92 59.0 100
2,000 27.82 51.9 94.3
4,000 25.84 44.7 88.8
6,000 23.98 37.6 83.6
8,000 22.22 30.5 78.6
10,000 20.57 23.3 73.8
12,000 19.02 16.2 69.3
14,000 17.57 9.1 65.0
16,000 16.21 1.9 60.9




http://www.staginglight.com/guide/air.html


All we have done is taken the timeslip and put all cars at the exact same standard, no advantage from temp or altitude

Ted Baldwin

.............something tells me that if your car was actually running the fastest times you will be less interested in the correction factor. If you picked up your E63 and it ran 11.5 @120mph, you won't be correcting your time and publishing how much slower your car is compared to one that ran 12.4@114 as eagerly as you are now doing.

Ted

juicee63

absolutely false..

I will correct my times until I am fitted with my sneaky peete

I own a CLS 63. And it will stay right with your modded 55 according to my calculations , J/K

I know I would get waxed by most of you guys , that is not the point. I know the correction to be highly accurate because I was running 13.6@104
@Palmdale , I corrected and guess what? I ran real close to my dial in Sac..

12.61@113? How on earth can this happen a full second?

I calculated my 1/8 mile runs to the 1/100th, I know what my car will do each and everytime because of my calculations. They are not guesses or folly nor wierd science. Physics, Algebra, Meteorology.

I would bet some huge coin my car will hit the 12.36@115 when condition is right, coming this fall..This is my fastest corrected(adjusted) slip, the 1.69 60 ft is still an anomoly, sad sad sad..

you guys certainly do not have to use any of this and I am not trying to make you accept it. Just understand it has helped me alot and many others. It has its limits and ofcourse it does not mean your car will run the corrected time, it just gives you a standard consistant benchmark to shoot for. Hats off to guys posting up DA, its very helpful

rflow306

You still don't understand they are correcting the actual track altitude a constant for the listed venue not the DA

You are using the DA and applying it to the elevation that it matches, to compare different cars at different tracks. The da should be used at the track to compare your specific runs against other previous runs with different da's to gauge the cars current performance level. Most of the people who race heads up use the data plots to confirm when the car is down on power, not because of the weather but mechanically.
Just so you understand, they have several da readings for that specific track for different days, the day of the event the da is x their 60 ft is y and Z is trap speed, lets say you have points which match x and y so z must also be close. If they are not close you know your problem lies elsewhere and is not weather related.

You would be surprised the amount of data a pro-stock team gathers throughout a racing season, but one thing is for sure they like many people who race could care less what their car would run with a magical DA correction factor.

enzom

Juicee - I am looking, but I only see "Altitude" which is a measurement unaffected by temperature or humidity. You keep saying it is a DA chart. I don't see denisty altitude. I only see altitude. What am I missing?

And what calculator are you using that requires you to input temp and humidity? I don't see it on the NHRA website.

I am obviously not a fan of these adjustments, but if I am going to be fair about it, I'd like to make sure that I completely understand how you have been applying the NHRA altitude adjustments to real timeslips. I doubt I will change my mind, but I will at least understand more fully how you are applying these correction factors.

zoink

Pardon my ignorance if my statement below is completely wrong.

No matter how accurate you measure DA.... DA will only standardize the altitude factor, while ET & trap also and greatly depends on track condition, car's condition & setup and driver.

So yeah, I agree w/ juicee63 to some extent.... just to make the numbers more comparable.... but DA cannot be used for claiming the bragging rights Faster is faster.

juicee63

The Density altitude calculation is simply taking the car and placing it a SAE condition, it is a constant the only variable is what it measures. Just because the NHRA chooses to list an Altitude correction table does not mean using a DA calculation based on weather info at the track is inaccurate or a guessing game. The actual altitude measurement of all the tracks is done using standard atmospheric pressure conversions. do you actually think the track is exactly 3700 ft or 1600 ft or 5800 ft above sea level? The DA calculation converts to ALTITUDE and then uses the very table you posted to correct the time slip. I understand a pro racer or heads up racer has much more precise tools available and likely has no need to measure DA.

Everyone I have been around that takes this sport seriously had some type of DA meter. Obviously it is useful. And it does help compare your run to other runs you have made at the same track over the course of a season.

It also can be used to get the cars all running under the same standard. Once again same cars , same track , same day, just run heads up, no correction needed to see who is faster. I would want to correct everytime to see how my run stands up against other runs in my car. I think we do it a bit differently out here, much more ET racing vs heads up. Maybe that is why you see all the DA meters here?

juicee63

Very true..

the Altitude table on the NHRA website is Taken from air density measurements and based on standard atmospheric condition, you get altitude by plugging in this

This table relates the density of an average day at sea level (59 degrees, 29.92 inHg) and how it changes at different elevations in the atmosphere.

29.92 59.0 100

1. temp 59.0 F
2. humidity 100
3. Barometric Pressure 29.92

The Density of the Air equates to an Altitude and the correction factors produced on the table are directly from the input of the standardized variables

rflow306

Bro, altitude is altitude the correction factor is the multiplier to correct said altitude to sea level. You don't think the track at Denver, CO for example is not 5800 ft above sea level do you?.

enzom

I will let Ranger speak for me. He knows a thing or two about racing.

BTW, glad this discussion isn't limited to MB's.

http://forums.corvetteforum.com/show...p?p=1561769859

Peace out.

juicee63

Lets study this more fully .
The NHRA website uses an Altitude table, the altitudes oddly at every track are rounded off, ok no big deal.

By calculating Air Density we will get a corresponding altitude, here is the info and the calc.

Once you read everything you will realize the table provided by NHRA actually comes from SAE.

with the corresponding altitude we can use the table to correct the times

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

rflow306

Juicee here is some food for thought so that you can understand better.

http://en.wikipedia.org/wiki/Altitude

Here is another good read about the subject.

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

juicee63

Altitude is not Altitude, in order to get altitude you must use a measurement,



In most cases the tracks are likely measured based elevation of surrounding locations. This measurement is taken by using an International Standard of Mean Sea Level.

The barometric pressure sensor allows the user to track recent changes in ambient air pressure. This allows the unit to calculate a precise altitude reading when properly calibrated.

This is what it does , those correction factors you posted are the exact same factors I use. Altitude can easily be calculated based on ambiant air pressure, temp and humidity. It is Science not folly , Are you suggesting Density Altitude is not there?

juicee63

funny we are qouting , reading the same sources...What is helping is reading the 6 speed forum, I understand now....

I still Like DA vs Altitude, Im going to argue over there too :-D

Thanks for being civil

juicee63

seems a bit more even over there LOL....

Thanks man , this helps alot.

I see where the DA stuff is helpful and also could be really off. But so could the Altitude correction used w/o weather data. Bottom line is you must understand what and whay you are correcting and do it consistantly. I will stick to DA calculation and cross check that with the info and posted temps on the slip, so far they have all been really close , guy says it was 78 the weather station says 78, This is cool stuff.

I guess I need to listen to you guys as I clearly see where the weather correction can get silly

juicee63

He still Adjust for altitude..Funny he lists the DA on his fastest slip a mere negative 1/8th mile under the SAE sea level

juicee63

The more I read the more I stand by the DA correction vs altitude.

Altitude is a starting point

This poor ******* is running his Vette at the equivalant of 9000 feet!!!!

Do you have any ide how flippin slow your E55 would be at 9000 feet?

Your car in New Mexico would never break 13 seconds at a 9000 DA. would you be against some adjusting then?

Seems all the folks against adjustment reside near a sea level track, hmmm

http://www.mustangforums.com/m_179265/tm.htm

Bluemax

I think some of you are a little confused what Juice is trying to get the point across, First, The only heads up racing in the NHRA are the pro classes ( Top fuel, Achohol and Prostock). All others race with an index factor provide by the NHRA. This Index is the way to level the playing field for each given class at each track.

Take a look at this website www.ifamilysoftware.com These are the people that sell some of the best weather stations around for the money.There are some good reads there but take a look at (Racing with weather computers )My personal weather station has a pager the transmits the weather updates every 10 Seconds. And for the people with those hand held stations should throw them away. How can you get an accurate reading while your waiking around the staging lanes with a monitor thats reading body heat, engine temps and other factors. My weather Station is 6ft above my trailer and trying to get it above 10ft for next year.

juicee63

So you REALLY calculate DA?
wow thanks for the link,

I think the guys question the accuracy more than why I am doing it. Honestly the more forums I read I really think I did this the best way, taking all the slips and putting all the 63 cars on the same track @ sea level. It may be a tad off but with your new weather stuff I can also do more accurate adjusting based on real time track data vs weather data 15 minutes prior from several miles away or even more. I was simply trying to standardize the 63 times since we were all running at different tracks. From what I have seen my numbers are really close. I know you will hit 12.3@116, yep and it will happen with good air. How do I know? Cause I have done about 700 corrections and I can say this run is very likely. My dial time in AZ at SpeedWorld will be based mainly on DA, and what I have on paper. the car runs what it runs but that will vary by nearly 2 seconds due to AIR only. This is why getting an accurate DA reading is critical in choosing a dial time and or simply making the decision to go to the track at all.

lbE55

My head hurts.

juicee63

http://www.ifamilysoftware.com/

Just what I need more TOYS