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Thread: HP loss at high altitudes

  1. #1
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    HP loss at high altitudes

    Is there any way to calculate how much power a normaly aspired engine losses at higher altitudes? For example: Denver Colorado or Mexico City, they're both about a mile above sea level.
    "NEVER ALLOW SOMEONE TO BE YOUR PRIORITY, WHILE ALLOWING YOURSELF TO BE THEIR OPTION"

  2. #2
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    i have no idea but wouldnt it be minibal and be countered by the same reason on the altitude?
    Don't bother me, I'm probably working while posting...

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  3. #3
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    http://www.webcalc.net/calc/0757.php

    Not sure of the formula, but I found this calculator.

    I found another page:
    http://www.ifsja.org/tech/misc/formulae.shtml
    Horsepower loss at altitude:
    Note: elevation in feet.

    hp loss = elevation x 0.03 x hp @ sea level
    1000
    "We went to Wnedy's. I had chicken nuggest." ~ Quiggs

  4. #4
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    Quote Originally Posted by johnnynumfiv
    http://www.webcalc.net/calc/0757.php

    Not sure of the formula, but I found this calculator.

    I found another page:
    http://www.ifsja.org/tech/misc/formulae.shtml
    Horsepower loss at altitude:
    Note: elevation in feet.

    hp loss = elevation x 0.03 x hp @ sea level
    1000
    Fantastic dude, thanks
    "NEVER ALLOW SOMEONE TO BE YOUR PRIORITY, WHILE ALLOWING YOURSELF TO BE THEIR OPTION"

  5. #5
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    turbo'd engines and to a lesser extent super charged engines will be affected less, the turbo will take longer time to make max boost but once that boost is reached torque/power levels should be comprable to one at sea level, since the turbo is designed to reach max boost at a certain rpm and maintain that till redline (most turbos however will drop in boost at higher rpm due to crappy wastegates or hardcoded ecu)

  6. #6
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    Quote Originally Posted by KnifeEdge_2K1
    turbo'd engines and to a lesser extent super charged engines will be affected less, the turbo will take longer time to make max boost but once that boost is reached torque/power levels should be comprable to one at sea level, since the turbo is designed to reach max boost at a certain rpm and maintain that till redline (most turbos however will drop in boost at higher rpm due to crappy wastegates or hardcoded ecu)
    Exactly, that's why I just asked about normaly aspired engines. Turbo and Supercharged engines generaly don't care at what altitude the road your driving on is
    "NEVER ALLOW SOMEONE TO BE YOUR PRIORITY, WHILE ALLOWING YOURSELF TO BE THEIR OPTION"

  7. #7
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    Quote Originally Posted by KnifeEdge_2K1
    turbo'd engines and to a lesser extent super charged engines will be affected less, the turbo will take longer time to make max boost but once that boost is reached torque/power levels should be comprable to one at sea level, since the turbo is designed to reach max boost at a certain rpm and maintain that till redline (most turbos however will drop in boost at higher rpm due to crappy wastegates or hardcoded ecu)
    but it cant breath!

    jk, idk
    pondering things

  8. #8
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    Quote Originally Posted by taz_rocks_miami
    Exactly, that's why I just asked about normaly aspired engines. Turbo and Supercharged engines generaly don't care at what altitude the road your driving on is
    They do if you are pushing along at max boost all the time
    The turbo is setup to provide boost up to wastegate pressures. BUT the amount of boost is determined by the speed of the impellor ( driven by exhaust gas speed ) and the wastegate control.
    So trubos take longer to get the bosst going and dont' initially increase power at the same rate as at ground level. ONCE the turbo is spinning fast enough and producing enough boost for the wastegate to want to blled some off THEN it is at the same power as sea level. So at higher alts they tend to be more laggy and more peaky.
    BUT with MODERN ECUs this often re-maps and shifts the wastegate actuator electornically ( as opposed to earluer/cheaper mechanical )

    on n/a modern ECUs can alleviate the problem of altitidude reduction in O2 but not remove it completely. So todays cars are a LOT better than older gen. I've struggled over [damn can't remember the name - pass on the road from Colorado Springs up to Breckenridge] in a rental 4-potter, I thought we were going to have to get out and push it was so gutless
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  9. #9
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    I also have a question about hp. Is it that every degree above 100 degrees (air temperature) the engine losses 1 hp for every 1 degree over. don't know if this statment is correct.

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    Quote Originally Posted by Matra et Alpine
    They do if you are pushing along at max boost all the time
    The turbo is setup to provide boost up to wastegate pressures. BUT the amount of boost is determined by the speed of the impellor ( driven by exhaust gas speed ) and the wastegate control.
    So trubos take longer to get the bosst going and dont' initially increase power at the same rate as at ground level. ONCE the turbo is spinning fast enough and producing enough boost for the wastegate to want to blled some off THEN it is at the same power as sea level. So at higher alts they tend to be more laggy and more peaky.
    BUT with MODERN ECUs this often re-maps and shifts the wastegate actuator electornically ( as opposed to earluer/cheaper mechanical )

    on n/a modern ECUs can alleviate the problem of altitidude reduction in O2 but not remove it completely. So todays cars are a LOT better than older gen. I've struggled over [damn can't remember the name - pass on the road from Colorado Springs up to Breckenridge] in a rental 4-potter, I thought we were going to have to get out and push it was so gutless

    So to cut it short, forced induction has to work harder to make the same numbers, but since its forced induction theres less loss overall?
    I am the Stig

  11. #11
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    Quote Originally Posted by fpv_gtho
    So to cut it short, forced induction has to work harder to make the same numbers, but since its forced induction theres less loss overall?
    I hate it when someone takes my beautifully crafted, researched and worded engineering analysis of an issue and it's solution and THEN summarises in in ONE sentence -- especially when THAT sentence conveys the message best
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  12. #12
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    when i read the thread's title i thought it was about HP/Compaq stock going down !!
    ----R.I.P----
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  13. #13
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    Quote Originally Posted by Misho
    when i read the thread's title i thought it was about HP/Compaq stock going down !!
    lol....

  14. #14
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    Quote Originally Posted by Misho
    when i read the thread's title i thought it was about HP/Compaq stock going down !!
    Please don't ..... that subject is taboo, as an ex-HPer I've far too much invested in the company for you to make jokes like that
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  15. #15
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    But I wasnt joking, i seriously though that is what the thread is about !!
    ----R.I.P----
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    2003 - 2004

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