You're arguing with yourself again, Zig.

I'd suggest you consult Dr. Irwin Corey, or his esteemed colleague Gyro Gearloose.

 

zig if you correct isnt it the same as un corrected. everybody says some tracks are better. but even those tracks correct better. some things you just know. i never personaly went in space to see if the world is round but i know it is

 

Dennis, what Zig is referring to is correcting for air density. Tracks that are at sea level enjoy nice, dense air. Tracks that are at altitude, such as in Denver, are 5000 feet above sea level, so the air is much thinner. Thinner air has less oxygen content, so you get less power.

Temperature and humidity are also a factor. Even at the same track, you will run better on a cool day in autumn than a scorching day in August.

There are several ways of measuring the air density, but nowadays many users employ a hand held device that will give you the effective air density at any point in time. Then by applying a correction factor (see the tables that Zig posted), you can correct your actual time to see what you would have run at sea level.

Correcting for air density applies much more to ET for the full quarter mile than it does for your 60-ft time. According to the tables that Zig, a 1000 ft. difference in air density would change a 2.00 short time by less than 3 hundredths of a second.

Here's the math: Let's say you go to the track in the morning, and the effective air density is at 1200 feet. You run a 2.0 second short time, which when you multiply by the correction factor of .9874, yields a corrected short time of 1.9748 (delta is .0252).

Now let's say your next run isn't until mid-afternoon, and in the warmer temps, the effective air density is at 2200 feet. Again, you run a 2.0 second short time, which when you multiply by the correction factor of .9744, yields a corrected short time of 1.9488. The delta this time is .026.

So even though at the track, you ran the exact same times on both runs, once you correct them for the effective air density, your car actually performed better on the second run.

 

hittman99 i get that. but how does a car dynoed at 5000 ft vs one at sea level have the same rwhp. or john force runs 4.80 at mile high but also runs 4.80 at english town. because it is tuned for it. say im stupid but i dont believe in correction. but i am not going to argue about it. i just know. because i know

 

The car that is dynoed at 5000 feet makes less power than the same car that is dynoed at sea level. However, when you see the same power it is because they have corrected both runs to sea level standard days (SAE).

As far as a funny car being as quick in Denver as at Englishtown, that's because the engines are supercharged and they are not affected as much at altitude. However, the cars are still quicker at sea level tracks as compared to Bandimere Speedway in Denver.

 

Nice job of sorting. But corrected times do not correct for launch techinques, traction & etc as previously posted by LS1LT1....we are going in circles I'm done

 

But we are looking at comparing two of Zigs time slips with each other. Therefore, they do not have to be corrected But he must have corrected time slips....... I have two posted in the 1/4 mile performance thread that we can correct to compare to his........ my final answer

 

But this is the Corvette Forum we have to correct the correct so that it is correct even though we have no time slips to correct

 

tommyd i still take the stand i don't believe it. even with prof i still dont
believe.
glennhl even pro stock their is not that much difference and some pure stock classes hold et and mph records for the whole nhra at mile high. there is almost a second difference on the 1/4 mile performance times yet less than a 10th in all other classes. when the car comes from another region that ran slow and goes fast here than i still wont believe. and all the record holders of the many classes nhra and ihra run they are all over the usa not just one track yet those classes are run at every track please explain

 

Dennis, maybe you don't believe, but those pros sure do. They measure the air density every few minutes. Many tracks that run national events even post the DA on an electric sign so everyone can see it.

You have to remember that Funny Cars like John Force's have a ton of horsepower to play with, so when the air is bad, they can compensate by changing clutch settings, blower pulleys, spark advance, nitro mix, etc. They do this for a living, and know their stuff inside and out.

The average weekend warrior just goes to the track, climbs in the car, and punches the gas. Very little real tuning goes on.

One other thing that you might not be understanding. "Corrected times" are only used for comparison purposes, not for the record. If you're racing in Denver, they are recording the actual times you run, not the corrected times. But if you're a forum member bragging about your car, you might say --- I ran a 12.xx in Denver, and that's the equivalent of Joe Doaks, who ran a high eleven at Englishtown.

 

Let's just look at the top qualifiers in Pro Stock in Denver, then the next two races in Seattle and Sears Point (Infineon).

Denver: 7.062 at 195.65
Seattle: 6.69 at 206.80
Sears Point: 6.63 at 207.82

Over 4 tenths and 12 mph in trap speed. Sorry, doesn't seem like "not much difference" to me. That's huge!

 

part of that could be track conditions or weather not just altitude

 

i've been out of town for a bit, so i'm just catching up.

but this (dennis50nj's comment) summarizes my feelings about using timeslips to 'prove' the existance of tm.

anyone care to discuss launch techniques, and there effects upon times.

 

now that we have a discussion going, what would my 'slips' prove/disprove ?? nothing more than that i'm either a better or worse driver than the next guy. it will not prove/disprove the existance of tm holding the car back.

 

i have also heard that folks claim that they can't get as good of times with the c6 as they did with the c5. wasn't there a tire size change between the two ? am i wrong or did the c5 have 18's in the rear but the c6 has 19's. wouldn't this help explain why folks are having difficulty achieving the same times that they once did in their c5.

 

So first you're saying that you need to correct the timeslips for altitude, but you're also agreeing with Dennis that such corrections are bogus?

The timeslips don't prove the existence of TM, but they do provide evidence that despite many changing variables, 60 ft times for a given car are remarkably consistent from run to run.

We have already discussed launch techniques, and I have yet to hear anyone contradict the premise that brake torqueing at launch offers little or no advantages over leaving from idle or near idle. Of course, if you could find your timeslips, and remember the barometric pressure, temperature, humidity, wind, tire pressures, track consditions, time of day, phase of the moon, and orientation of Saturn to Mars, you might be able to correct your times, and thus offer us a cogent analysis of proper launch technique based on your scientific observations and deep understanding of Newtonian physics.

As to the claims that the C6 is slower than the C5, that's ridiculous. I haven't heard of many stock C5s running in the low twelves. Of course, all those times you posted are uncorrected, so I guess they don't mean anything.

Also the tire height for the 19's on the C5 is the same as for the 18's on the C5. Of course, those tire heights are not corrected for the air inflation pressures, so that may also be in doubt. Also, the wheels are different, and probably don't weigh the same. More confusing variables to consider. Suspect you might need a vector processing supercomputer to figure it all out.

Knock yourself out.

 

Just look up on the NHRA site and you'll see exactly how the NHRA corrects for altitude. It's significant. People that run on sea level tracks do not want to admit that altitude affects performance, but believe me those running in Colorado sure know the affects.

Plus, if anything, the track conditions are typically pretty consistent at NHRA national events, they work hard for consistency. I agree weather still affects the performance, that's why I listed the following 2 races.

http://www.nhra.com/tech_specs/altitude.html

 

no, i followed this exchange...

"Over 4 tenths and 12 mph in trap speed. Sorry, doesn't seem like "not much difference" to me. That's huge!"

"...part of that could be track conditions or weather not just altitude"

why can't the same resaon be used to explain TM ??

can you clarify the changing variables, are those variavbles enough to make a difference.

i have quoted some sources that discuss the benifits of brake torqueing and preloading.

i wasn't trying to say, stock-for-stock, the c5 was faster, what i tried to say was that some c6 owners claim that their times are not as good as they were getting with the c5 and therefore it was tm holding the c6 back. i didn't say, nor do i believe it. it has been said by others on this board.


the tire height and diameter are the same ?

ok, good. in that case, tire size can not be used as a reason for the variance between the c5 and c6 times. i have heard numerous members claim that they were getting better times in their c5 and that tm in the c6 is the reason for this.

 

Here are some results from my runs. The best and worst on a given date.

Date 7/28/06
Time 10:30 PM
60'----1.99
330'---5.53
1/8----8.36
MPH---87.07
1000---10.79
1/4----12.82
mph---111.19

Date 7/28/06
Time 8:53 PM
60'----2.01
330'---5.52
1/8----8.34
mph---87.25
1000---10.81
1/4----12.92
mph---107.78

Track condition almost identical on both runs, maybe a D/A difference of 50 feet, around 800ft. On the second run though the car really fell on its face on the 2nd to 3 gear shift. Can this be TM.

Another day.

Date 5/10/06
Time 6:26 PM
60'----2.01
330'---5.56
1/8----8.50
mph---85.74
1000---10.97
1/4----13.04
mph---109.15

date 5/10/06
time 8:32 PM
60'----2.01
330'---5.79
1/8----8.74
mph---84.11
1000---11.26
1/4----13.35
mph---107.07

On this day D/A was around 1300ft and stay constant throughout the evening. On the second run it fell on its face on the 1st to 2nd shift.

For runs in May the car was still stock. For the July runs I had added a Vararam and a Tune. But I also had added at least 100lbs of sound proofing. These runs are at the same track and temps where similiar in the 60's.

Launch technique in May was smash it and go. Best 60' is 2.01 with the worst being 2.10. In July I preloaded to around 1200rpms except for the first run which was the tech I did in May and that was a 2.06. Using the preload method best 60" is a 1.98, worst is 2.01, much more consistant.

All runs where made with TC and AH off and the car shifting itself. I don't know what caused the car to bog like that but it sure felt like someone had there foot on the brake. I might get one more time to run this year, will have to wait and see.

 

glennhl you are right about one thing i live on the east coast and im sticking to my story