Puppeteer

Author Topic: altitude vs. HP  (Read 6576 times)

mike90045

  • Mendocino Metro
  • Hero Member
  • *****
  • Posts: 1594
  • Mmmm BBQ
    • View Profile
    • Mikes Solar PV page
altitude vs. HP
« on: July 24, 2007, 02:20:46 PM »
Available HP decreases with altitude above sea level so if you are at any appreciable altitude then your generation capacity will also decrease.
Ron   

  Anyone know the caculation for reduction of HP as you gain altitude ?


phaedrus

  • Sr. Member
  • ****
  • Posts: 278
    • View Profile
Re: altitude vs. HP
« Reply #1 on: July 24, 2007, 05:31:41 PM »
People have a range of rules they follow on this Mike. They're all fairly close to oneanother. My understanding is that ya generally don't count the first 1000 feet. After that, according to my "rule" it's about 3% per 1000 feet.

Air Density decreases at a rate of 2.9% - 3.0% for each 1000 ft. of elevation above Sea Level.
Atmospheric Pressure's about 14.5 psi for flatlanders (14.7 at MSL)
Atmospheric Pressure @ 9000 feet = 10.5 psi
Pressure Loss = (14.5 - 10.5) = 4.0 (4.0/14.5) = 27.58 % @ 9,000 feet

An engine sucking cold air and/or with a tuned intake can overcome this a bit. Using the higher CR in a l'oid (COV closed) also helps.

Unless you're well up in the hills (like > 4000 feet) I don't think it's going to be a problem.


 
if ya don't ask permission they can't deny it...

Stan

  • Guest
Re: altitude vs. HP
« Reply #2 on: August 08, 2007, 03:35:49 AM »
Also Mike, don't forget that if you have a fan turned by a pulley on the crankshaft, it'll take 1/3 hp away.
Stan

cujet

  • Hero Member
  • *****
  • Posts: 957
  • Lister power rules!
    • View Profile
    • www.cujet.com
Re: altitude vs. HP
« Reply #3 on: August 16, 2007, 09:14:47 PM »
While cold air will help produce power, the colder air at altitude is figured into the 3% per 1000 feet loss. A standard day with standard pressure (STP) is 59 degree F. and 29.92 inches mercury. As you go up in altitude the pressure decreases along with the temperature.

Higher compression can help a very small amount. Also less restrictive intake and exhaust. But, the bottom line is simply a significant power loss at altitude.

Chris
People who count on their fingers should maintain a discreet silence