Being at 4700ft above sea level in good ol Salt Lake City, we tend to have cars running way lower than they should. For example my buddy has a FD. It ran a 10.1 at bandimere (even higher elevation) but usually averages out a little higher. Now in seattle he pulled a 9.89 1/4 mile. And here in Utah he took a stock S5 TII in excellent running shape and ran a 16 flat. He is by no means a bad driver and I've been to the strip and seen cars run what would seem like bad times. I know elevation affects performance. And that turbo's are less affected. What are actual figures or whats the formula to how much time you actually lose at 4700ft.

 

http://www.twinturbo.net/net/viewmsg...&msg_id=752270

 

for hp/weight vs ET, check net.

power vs elevation:

power is mostly based on air density in the manifold, which is ambient + boost (ignoring various losses). At 4700 ft, ambient is 12.35 psi. Assuming same ambient temps, a na engine would only make 84% of it's sea level power (12.35/14.7) . For turbos, power is based on ambient + boost pressure. 4700 ft power for various boost pressures:

10 psi ... 90.5%
14 psi ... 91.8%
18 psi ... 92.8%
22 psi ... 93.6%

At Breckenridge Co, elevation is 9600 ft with ambient pressure at 10.3 psi, and an na would only make 70% of sea level power. At 14 psi, turbo would be at 84.7% power.

Many new turbo cars are designed to make same power at all reasonable elevations, with boost increased to hit mass flow or absolute pressure (ambient + gage) targets.