Engines at altitude
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Joined: Jan 2005
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From: Van nuys, CA, U.S.A
Engines at altitude (searched and FAQed)
I've already searched and I did'nt find an answer, I'd be really happy if someone answered my questions.
Since atmospheric pressure is 14.7 at sea level and more like 11.7 at 5,000 Ft elevation, would'nt the first 3 PSI of boost go to waste? Well, not go to waste, but if you're somewhere where the atmosphereic pressure is 11.7, would'nt the first 3psi of boost do nothing but fix the elevation differeance (while adding power)
I have another question, theres this 'rule of thumb' I heard about that says you lose %3 of power for every 1000FT of altitude, do you guys think this is true?
My third question, let's say you have a 100 HP all motor engine and you go to a really high altitude, high enough that your engine makes more like 70 HP... if you boosted your motor to add only 30 HP and ended up having 100 HP at that high altitude, would the engine be reliable as stock since it's making only 100 HP?
I'm not 100% sure if atmospheric pressure at 5000FT is 11.7, so if you know the correct pressure, please correct me.
Modified by Raf at 10:47 PM 1/3/2005
Since atmospheric pressure is 14.7 at sea level and more like 11.7 at 5,000 Ft elevation, would'nt the first 3 PSI of boost go to waste? Well, not go to waste, but if you're somewhere where the atmosphereic pressure is 11.7, would'nt the first 3psi of boost do nothing but fix the elevation differeance (while adding power)
I have another question, theres this 'rule of thumb' I heard about that says you lose %3 of power for every 1000FT of altitude, do you guys think this is true?
My third question, let's say you have a 100 HP all motor engine and you go to a really high altitude, high enough that your engine makes more like 70 HP... if you boosted your motor to add only 30 HP and ended up having 100 HP at that high altitude, would the engine be reliable as stock since it's making only 100 HP?
I'm not 100% sure if atmospheric pressure at 5000FT is 11.7, so if you know the correct pressure, please correct me.
Modified by Raf at 10:47 PM 1/3/2005
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Joined: Apr 2004
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From: phoenix, az
Re: Engines at altitude (Raf)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Raf »</TD></TR><TR><TD CLASS="quote">I'm not 100% sure if atmospheric pressure at 5000FT is 11.7, so if you know the correct pressure, please correct me.
</TD></TR></TABLE>
Here's a rule of thumb i found in an air conditioning book.
You would need a aneroid barometer and some conversion factors to be exact.
A tube of Mercury at sea level (14.696 psi) will read 29.92" Hg. As elevation rises the mercury column will start to fall. It will fall about 1" for every 1000 ft. altitude.
29.92" Hg (mercury)=14.7 psi
Convert inches of mercury to pounds per square inch (29.92/14.696=2.036)
Conversion factor 1 psi=2" Hg
atmospheric pressure at 5000 ft is 12.5 psi according to the formula.
</TD></TR></TABLE>
Here's a rule of thumb i found in an air conditioning book.
You would need a aneroid barometer and some conversion factors to be exact.
A tube of Mercury at sea level (14.696 psi) will read 29.92" Hg. As elevation rises the mercury column will start to fall. It will fall about 1" for every 1000 ft. altitude.
29.92" Hg (mercury)=14.7 psi
Convert inches of mercury to pounds per square inch (29.92/14.696=2.036)
Conversion factor 1 psi=2" Hg
atmospheric pressure at 5000 ft is 12.5 psi according to the formula.
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