How much does elevation really effect the performance of a car,airs more dense,i ride trials and for us it really doesnt make a huge difference except when you approach 8,000 to 10,000ft in colorado,and even then, change the jets and your good

 

in normaly asperated cars above a certain elavation performance starts dropping off alot because the air is less dense which means the oxygen molecules are father apart so you cant get as many in the combustion chamber less air means less fuel....now
With turbo charged cars the elevation effect is probly unnoticable because the turbo is basicaly a pump...the big difference between N/A and Turbo cars is that the Naturaly aspirated car has to suck the less dense air (normaly 14.7psi at sea level) where as if a turbo car runs 20 psi normaly it will problly still run at 20 psi..."but the turbo will have to work harder you say" no the turbo will spin faster but it wont be working much harder because less dense air is easier to pump....so unless you get to really high elevations you probly wont notice much difference with a turbo car

 

The atmosphere looses about 3% per 1000 feet. Check thi site.

www.grc.nasa.gov

search for "interactive atmosphere model"