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Elevation loss figures

Old 10-16-04, 11:35 PM
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Elevation loss figures

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.
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Old 10-18-04, 09:20 AM
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http://www.twinturbo.net/net/viewmsg...&msg_id=752270


Originally Posted by flamin-roids
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.
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Old 10-19-04, 03:26 PM
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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.
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