How much horspower do I lose per thousand feet of altitude?

Discussion in 'General Bike Related Topics' started by FloydV, Nov 27, 2011.

  1. FloydV

    FloydV Donating Member

    Messages:
    1,974
    I just moved from a city at 5,000 feet above sea level to one that is 3,000 feet above. How much horsepower do I gain for the 2,000 foot decrease? Is there a formula to calculate the loss or gain for an increase or decrease in altitude?

    Someone posted a formula, but it has been so long ago that I can't remember it.
     
  2. lovelessjl

    lovelessjl Registered

    Messages:
    112
    HP Loss = (elevation x 0.03 x horsepower @ sea level)/1000
     
  3. Lucid

    Lucid Registered

    Messages:
    609
    After guessing low on my off nitrous hp (haven't dyno'd with mods), I'm losing 6.92868hp just for being in Oklahoma. (while we're doing math, anyone care to figure out what I put in as my hp?) I will paypal you $1.

    Edit: @1276ft.
     
  4. FloydV

    FloydV Donating Member

    Messages:
    1,974
    OUCH! Using your formula my equation would be: 2950 x .03 x 160 / 1000 = 14.16 hp loss. Meaning 160 drops to 145.84. 160 to 146.

    Guess I'll have to go turbo! Thanks for the info. :banghead:

    Floyd

    P.S. Guess this explains why my 95 Ranger V6 seems like it's become a 4 cylinder.
     
    Last edited: Nov 27, 2011
  5. lovelessjl

    lovelessjl Registered

    Messages:
    112

    Algebra isn't my strong suit but I believe you used 181 as your hp figure...keep the buck, you can buy me a beer if we ever meet up for a ride.
     
  6. dadofthree

    dadofthree Seasoned Beef Donating Member

    Messages:
    67,155
    Location:
    Barnwell, SC
    ??? :whistle:
     
  7. AJAY

    AJAY Registered

    Messages:
    2,625
    Location:
    Northern VA
    You did the math right, but made the wrong conclusion.

    Your horsepower is greatest at sea level and decreases as you go up in altitude.
    Say at sea level, your HP is 160.
    At 3000 ft, your power loss is 3000 x .03 x 160 = 14.2 resulting in 160 - 14.2 = 145.8 hp
    At 5000 ft, your power loss is 5000 x .03 x 160 = 24.0 resulting in 160 - 14.2 = 136.0 hp

    So, by moving from 5000 ft down to 3000 ft, you picked up about 10 hp.
     
  8. Lucid

    Lucid Registered

    Messages:
    609
    I think I did 182 but it comes out almost the same at 181. people just don't ever get rewarded for using math anymore!
     
  9. i live up above 6000ft. i love the feeling of sea level! feels like a 20+hp gain. :thumbs:
     
  10. frisbee

    frisbee GODSPEED RACING Donating Member

    Messages:
    16,660
    Location:
    Tacoma ,Wa.
    Thats the way I read it . You get better at sea level and you moved to a lower level right?



     
  11. jphilipson

    jphilipson Registered

    Messages:
    2,709
    see level for you would be closer to a 30 HP gain :laugh:

    I'm moving to death valley :thumbsup:
     
  12. jellyrug

    jellyrug Donating Member

    Messages:
    3,129
    Location:
    Pinehurst NC
    3% is a rough rule of thumb.

    The higher the RMP which hp is developed at, the more the altitude penalty will be.

    For expample it means a Duc 1198 will lose less hp than a GSX-R 1000 when going up in altitude.
     
  13. badass1000

    badass1000 Registered

    Messages:
    102
    about 3% per 1,000'. I am at 2,800' elevation in Boise, ID. I love going to sea level tracks or riding at sea level. Turbo is not really effected by elevation as long as the turbo is big enough to build the same amount of boost at elevation. I ride snowmobiles any where from 5,000'-9,500' elevation. Their is no comparing a turbo sled hp at elevation to a NA snowmobile no matter what engine mods and pipe they have.
     
  14. AJAY

    AJAY Registered

    Messages:
    2,625
    Location:
    Northern VA
    Some aircraft use what is known as a "turbonormalizer." This is a system that increases boost to keep the effective intake pressure the same as sea level. Thus an engine at high altitude produces the same horsepower as it does at sea level. Before the advent of jet engines, high-performance piston engined aircraft like WWII fighters used two stage compressors (turbo or supercharged, and combinations thereof) so that they could operate with decent power above 20,000 feet MSL.

    While a Busa just loses power as it is operated at higher altitudes, airplanes have competing factors. My plane loses significant power as it is operated at higher altitudes, and less power means lower speed. At the same time, the lower air density also allows the airplane to move faster relative to the ground, so losing power but also losing drag. A magic combination happens about 7000 to 8000 feet MSL, where the reduced drag more than makes up for the loss of horsepower, resulting in the fastest speed. (which is, sadly, just a tad lower than a Busa at sea level :(. But then I can go 175 all day without fear of a speeding ticket or wiping out in the turns! :))
     

Share This Page