Still trying to pick a track for this Friday night. What kind of difference will 900 ft compared to 600 ft compared to 30 ft matter? Some of the colder places have higher altitudes so I am trying to weigh the temp/altitude issue. Since I'll be driving 1,000 miles, I want to make the best choice possible.

The tracks should be SAE corrected. Someone correct me if I'm wrong.

Oops, I'm an idiot. Dyno's are SAE corrected, it'd be too hard to do that for tracks I think.

You can be off a good half a second depending on the altitude because of the lack of oxygen from what I've seen from none S/C'ed E55's. Guys from Dallas compared to Houston and what not.

Tracks are not corrected on the slips you receive at the track. You can do your own corrections due to altitude at the NHRA web site. Check out this web site that calculates the air densities due to alititude, temp, and humidity. This gives a "density altitude" measurement so apples to apples comparisons can be made. http://www.wahiduddin.net/calc/calc_da.htm

You will find at the same altitude that air temperature affects the density of the air the most.

I guess what I am trying to figure out is if one tract is 8 degrees warmer but is at 30 ft versus the cooler track at 900 feet.

Most tracks have a "track record" web page....I would compare those records with tracks around the US including your own down there. Should at least help a little. So many variables including actual track prep ya know......gonna be a "close your eyes and put your finger on the map" call as to which track.

Worse comes to worse....find some of those track record guys "blah blah blah racing" call them and ask them. The locals would know.

Good luck man.

1000ft of altitude will adversely affect performance more than 8 degrees of ambient temperature.

-m

I agree with Marcus....go with Sea Level Derek....take it from a guy who ran 12.7 at 4300ft compared to your 11.7. Although this is wayyyy off scientifically, logically that would be about .25 sec with every 1000ft. Would hate to have you make that long drive and get killed by even 1000ft. More air makes that Kompress perform like she should....a BEAST!!

Thanks guys. That's exactly what I'm looking for. Looks like that pushes me to the coast and away from Rockford.

Let me know if you are going to be in the mid-atlantic region. I'd love to get some runs in myself

The concentration of oxygen at increasing altitude remains constant, at 20.9%. This suggests that oxygen levels are unchanged. This is not true. Basically, as altitude increases, the atmospheric pressure declines. While the proportion of oxygen in air remains unchanged, the actual amount of oxygen in air decreases.

Atmospheric pressure at sea level is 760 mm Hg, with the corresponding partial pressure of oxygen in air is 159 mm Hg (20.9% or 760 mm Hg).

Invoke the Ideal Gas Law
PV = nRT

assuming one Liter of air
oxygen concentration = moles per liter (n/V) = P / RT

R = universal gas constant = 8.3145 J/mole K

so to compare your oxygen concentrations at different pressure/temperature levels for different locations, plug your temperature and air pressure into the following formula

Oxygen concentration =

((atmospheric presure(mm Hg)/760) * .21) / (8.3145) (Temperature (Celcius) + 273))

The higher the number, the more your car likes that location. Hope that helps.

Gareth

holy *****, somebody was awake in science class

Wow. Let's just say that it took me 7 years to get my 4 year degree.

Who told you Rockford is at 900ft?

Rockford is no more than ~700ft above sea level... drive there, it's as flat as the landscape can get.

-m

With all due respect Gareth, I find your calculations as much laughable as they are incorrect.

First, you refer to approximation but it is infinitely divisible, unquantized, rigid, and absolute. Need I remind you that total energy of a bounded system, can attain only certain discrete values determined by the system.

It's as if you completely rewrote Heisenberg's Uncertainty Principle to fit your own beliefs.

Let's set the record straight..... The probability distribution of an observable in a given state can be computed from the spectral decomposition of the corresponding operator. AFTER AND ONLY AFTER the measurement is conducted, the system's state will be an eigenstate corresponding to the measured eigenvalue.

Granted, your intial premise that the operator corresponding to the energy observable, plays a prominent role.....a state of the system is a unit vector in that space, and every observable is represented by a self-adjoint densely defined linear operator on that space.

Listen, I certainly don't mean to start a flame war, but I feel this post pretty much ends this debate.....bottom line.....The probabilistic nature of the mechanics predictions cannot be explained in terms of some other deterministic theory, and do not simply reflect our limited knowledge. It only provides probabilistic results because the physical universe is itself probabilistic rather than deterministic.










Had ya going didn't I......ahhh, I'm as stupid as an ox....I just copied the rantings of Stephen Hawking. I only wish I could be half as smart as you Gareth...just busting your chops.

Derek, my 5 year degree took 6. No worries. All the best people stay a little longer. I just enjoy this stuff.

Jakpro, I was about to quote you the stastical probability of your head being lodged far up your... but I rolled over laughing at the end there. Good one.

Of course my little calculation goes out the door once you add what Hillsman's got running in his car. Just using Oxygen as the item that is limiting our slow little sedans... For me I need to work more on the skill factor first. Then I need to setup an appointment with Cory.

It's 756 ft. So it's 144 feet less than your example. Would that elevation still hold your example true?

Running into a problem now with TECH. Both NHRA and IHRA require lots a neat things like fire jackets and roll cages once a car runs under 11.50. I've talked with two tracks anonymously and they are rigid about it. Mentioned that they don't even give warnings, they just kick you out. I'd hate to drive 1,000 miles for one run, but I'll do it.

You had me at "With all due respect Gareth"

Derek, if you think they are going to boot you let off a little on each run until you get that perfect launch. I had to make a few passes like that in my Mustang. I didn't have a roll bar and I new I would get the boot so I just ran it until I hit that perfect launch and then stayed in it for the rest of the run. Got the boot but still had a few nice runs.

Derrick

Derek,

I didn't say 900ft really mattered either, I just said go with the higher temp, even though 8 deg doesn't matter. @ 700ft you are looking probably at a .5mph loss in trap speed, something that is also very easily done @ a 10 degree higher temp.

My friend Chris didn't get harassed at Byron until his Lexus SC300 was running 10.30s @ 136mph without a cage, at full weight. I've seen many cars run sick trap speeds there, so I KNOW the track is fast.

Here's a correction chart for you. I think going to a well prepped track should be your #1 priority ahead of deciding if less than 1000ft or 8 degrees matters. NOTHING is going to matter if the track sucks, OR if you are going to get kicked out after 1 run.

http://www.greatlakesdragaway.com/co...onfactors.html

-m

What is really funny is that the E55 is probably safer than most of the other cars running 11.50 w/ cages and all that crap. I'd rather drive an e55 through a wall than an 11-second Rustang w/ a roll cage.

Careful man. At those speeds almost anything is a death trap.

medici78 is right... out of all the cars I've seen wipeout at the track, it's the rusting muscle cars that are the ones who are most often going to get hurt bad. The NHRA is still living in the stone age by trying to tell us that a car like an SL65 needs a roll cage. It's a STOCK car. If Mercedes didn't give it a rollcage, and let's it run 155mph, it doesn't need a rollcage to run at the drag strip. The SL65 without a rollcage is 10 times safer at speed than almost all of those thrown together heaps at the drag strip.

-m

Is the NHRA a corporation or elected members or what?