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Altitude????

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Old Nov 29, 2002 | 12:18 PM
  #1  
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Default Altitude????

Does anyone have or know of a formula to calculate how much HP I lose at a given altitude? I live in Colorado at over 7000 feet above sea level. I have heard that you lose from 3-5% per 1000 foot in altitude change.
Any input appreciated. Thanks.
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Old Nov 29, 2002 | 12:46 PM
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Default Re: Altitude???? (Yano)

Its not quite as simple as that. Here's a link: http://www.csgnetwork.com/relativehpcalc.html

If its any help the NHRA ET Correction chart shows you would correct your run by the following: ET x .9125
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Old Nov 29, 2002 | 01:34 PM
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Default Re: Altitude???? (topgun)

I've wondered that too, in Denver too. I'm at about 6k feet. In fact was giving serious consideration to the Vortech supercharger to get some more air.

My Coupe still seems quick, but I'm sure we'd notice a difference at sea level.
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Old Nov 29, 2002 | 02:19 PM
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Default Re: Altitude???? (topgun)

If its any help the NHRA ET Correction chart shows you would correct your run by the following: ET x .9125
Hi topgun, Do you have a line to that NHRA site? :cheers:


[Modified by scool93535, 11:45 AM 11/29/2002]
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Old Nov 29, 2002 | 03:16 PM
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Default Re: Altitude???? (Yano)

Other factors do come into play, but the change in air density due to altitude changes cost you about 3% power per 1,000 feet.


[Modified by 6Speeder, 2:17 PM 11/29/2002]
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Old Nov 29, 2002 | 05:07 PM
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Default Re: Altitude???? (Yano)

I am located in Colorado Springs too. I have only had engines dynoed here but have never had a car on a chassis dyno. I have had three engines dynoed at Lanier's and one at McCabe Motorsports. The variance between observed power and corrected to std dyno has usually been 22% to 26%. The one that lost the least was supercharged. The altitude here makes a huge difference!
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Old Nov 29, 2002 | 06:22 PM
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Default Re: Altitude???? (Yano)

Here is a few more inputs:
http://www.performancesupply.com/nhraconv.htm
http://www.nhra.com/tech_specs/altitude.html
http://www.smokemup.com/auto_math/nh...on_factors.php
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Old Nov 29, 2002 | 08:17 PM
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Default Re: Altitude???? (scool93535)

If its any help the NHRA ET Correction chart shows you would correct your run by the following: ET x .9125

Hi topgun, Do you have a line to that NHRA site? :cheers:
[Modified by scool93535, 11:45 AM 11/29/2002]
Here's a link to the chart: http://www.gnttype.org/techarea/misc/altitude.html
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Old Nov 29, 2002 | 11:56 PM
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Default Re: Altitude???? (Bill Oxley)

I've wondered that too, in Denver too. I'm at about 6k feet.
You have a bad altitude! :lol:

Sorry... couldn't resist a bad play on words.
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Old Nov 30, 2002 | 12:24 AM
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Default Re: Altitude???? (Tom Steele)

Thanks guys!!!!! Looks like the supercharger is going to be a must!!!! :thumbs: :thumbs:

If I did my math correct it looks like I lose about 1.2 seconds in the ET and almost 8 mph in trap speed! :sad: :sad: :sad: :sad: :sad: :sad: :sad:


[Modified by Yano, 10:31 PM 11/29/2002]
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