Need to settle an argument with a buddy

[canacudaa]

Ok guys heres the question. If a car runs in the low 14's at 3000 ft above sea level, leaving it set up exactly the same without touching anything, is it going to run in the low 13s if u bring it down to 500 ft above sea level? Now, keeping in mind the city at 3000 ft has an average of 25% humidity, the city at 500 ft has an average of 85% humidity. Any comments would help....Thanks guys

[TreeFrog]

Whhhooooa!

Flashback to high school ...

If two Mopars leave denver at the same toime doing the same speed, one head East and one heads West....

[Bullitt-]

Not in my way of thinking UNLESS the TUNE was better for the 500ft to begin with.       

[Blackcuda]

That's a good one for Mythbusters, write into the show.

[4Cruizn]

 

[Pistol Gripper]

OK,  I'll rub a couple pennies together here.

If the car is tuned to run at 500ft, 85% humidity and runs 14's at 3000 ft, 25% humidity, then yes it COULD run 13's at 500 ft.  If it's tuned to run at 3000 ft. then I'd have to say it'd be too lean at 500 ft. to even run 14's again.

P.G.

[Challenger6pak]

Ok guys heres the question. If a car runs in the low 14's at 3000 ft above sea level, leaving it set up exactly the same without touching anything, is it going to run in the low 13s if u bring it down to 500 ft above sea level? Now, keeping in mind the city at 3000 ft has an average of 25% humidity, the city at 500 ft has an average of 85% humidity. Any comments would help....Thanks guys

I'll have to send this in to my daughters math class.  Maybe they can learn something practical. 

While I do not know the answer to your question I do know it can be answered.  Professional drag racers deal with this problem everyday and have to adjust to run consistent times in the quarter.  With no adjustments an educated guess on what will happen can be known.  I have a buddy who uses a laptop and computer program to figure these things out.  Software is available to do this.

[Chryco Psycho]

I live at 4000 ' , typically you lose approx .1 seconds / 1000 ' of altitude so asuuming you tune the car for  the altitude if a car ran 14.2 at 3000 ' you should see 13.95 approx at 500' 

[moparmaniac59]

I'd have to agree that the car would run faster the closer to sea level that you are. An engine is nothing but an air pump. The air is heavier & denser at sea level (greater barometric pressure) than at 3000 ft. Not sure how the humidity would fit into the equation or detuning/retuning the car. Atmospheric pressure is 14.7 lbs at sea level and much less at 3000 ft, so in theory it should run faster; IE: more efficiently the closer to sea level that you get.
                                                    professor bull-shi_

[moper]

I'm with CP and manic on this one. No way you'll see a full second IMO.

[Oldschool]

Another little item that gets overlooked a lot when talking altitude/air density and HP gain-vs-loss is air friction.  The nascar and Pro catagory drag guys have known this for years, but it never gets mentioned. A lot of the extra HP gained by the engine at the lower altitude/denser air tracks gets eaten away by "pushing" the front of the car through that same denser air.  It takes less HP to "push" a car through less dense air beacause there is less air friction against the car surface.  At lower altitudes, where the air is denser, the air is thicker and needs more HP to push the car through it. Hope that makes sense, but it is a fact............   Oldschool       

[GoodysGotaCuda]

The NHRA has a chart for figuring that out. Apparently its somewhat accurate, as long as the motor is tuned to the new conditions it should be somewhere

My 318 went 14.0 @ 95 @ 5,200 feet. Sealevel (which of course 0ft d/a 'aint gonna happen really) it 'would' go 13.0 @ 101 fwiw


Chassis Dynos are usually tuned to STD (if i remember right) rather than SAE...STD corrects for weather conditions for a reason. 

[heminut]

I live at 4000 ' , typically you lose approx .1 seconds / 1000 ' of altitude so asuuming you tune the car for  the altitude if a car ran 14.2 at 3000 ' you should see 13.95 approx at 500' 

There is a site on the web that calculates the difference you would run at different altitudes once you punch in a base time and altitude for your car, but I don't have the link anymore. On my car it was basically .1 second per 1000 ft. as Chryco said. I picked up .25 going from my home track at 4300 ft. to S.I.R in Tucson, which is at 3000ft., but the starting line prep at Tucson was MUCH better than at home which made quite a difference.

[canacudaa]

  awesome comments guys!!! Thanks for the imput. Keep em coming.

[Bullitt-]

I live at 4000 ' , typically you lose approx .1 seconds / 1000 ' of altitude so asuuming you tune the car for  the altitude if a car ran 14.2 at 3000 ' you should see 13.95 approx at 500' 

Ok guys heres the question. If a car runs in the low 14's at 3000 ft above sea level, leaving it set up exactly the same without touching anything, is it going to run in the low 13s if u bring it down to 500 ft above sea level? Now, keeping in mind the city at 3000 ft has an average of 25% humidity, the city at 500 ft has an average of 85% humidity. Any comments would help....Thanks guys
 

BUT you see the difference of "leaving it set up exactly the same " & "so asuuming you tune the car for  the altitude" does not answer the original question.