I was thinking about this question tonight. Will a car that is dynoed at sealevel dyno the same power at say 5000 ft elevation. The only thing I could think of is no, because the car is running slower therefore it has less power at a higher elevation. So if it does vary how much will it vary per ft say?

 

higher the elevation the less power, thinner air = less oxygen

 

yeah it sucks!! I ran a 13.00 ish in my b18c5 ek stock full interior at sea level,then i ran in Arroyo seco raceway in NM(4985ft elevation) and it ran a 14.50ish. It makes a lot difference thats why im going turbo now.

So yes it makes a huge difference depending on the altitude and temp,and also if ur are N/A or FI. I hits harder on N/A cars,then FI cars.

 

A little of topic...
How does relative humidity fit into the picture?

The same car gets dynoed at sea level.
1st run 80% rh
2nd run 20% rh

Would the second run make more power due to less moisture in the air?

 

Humidity plays a role; but is not nearly as important as temp and altitude.

as sayd above, power output changes because of oxygen content differences in the air wich changes density.
There are correctors for that though.
for example:

sea level----29.92 in.hg----59 *f(standard)
2000 ft------27.82 '' '' ----51.87
4000 ft------25.84 '' '' ----44.47
6000 ft------23.98 '' '' ----37.61

You can then calculate air density(lbs/cu ft)
2.7 x P/ T

P= psi
T= temp

 

not sure on this but i belive for every 1000ft of elevation you lose 3% of engine power.

 

Can anyone else confirm this?

 

comfirmed!