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  1. #1
    Chrisrokc's Avatar
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    Elevation: How big of a difference does it make?

    I would like to hear everyones thoughts. We all know it makes a difference for sure. But how much exactly rpm and mph wise per 100 feet?
    Last edited by Chrisrokc; 08-24-2007 at 01:11 PM.


  2. #2
    WATER WOODY's Avatar
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    Elevation makes a HUGE difference.Every 1000' up,you lose 3% hp.It varies but im about 300+ rpm down on my triple,compared to sea level @ my 4100' elevation.Plus im 12% down in HP.When i had my blown Mustang dynoed,i was at a 60 RWHP loss up here than at sea level. This is the kind of thing im fighting all the time. My boats are 3-4 mph slower up here.Its a pain in the azz,so all i can do is make the best out of it.

    Your question about every 100' is almost impossible to accuratly measure because of weather change etc....It would be alot easier to measure the loss if you were to climp up in 500' increments.Too many variables here,thats why i gave you every 1000'.

    My single has ran a best of 80.1mph @ 7180rpm with a corrected 5280'.Thats spinning a 14/25 setback and my EFI on the red was all the way up.

  3. #3
    Chrisrokc's Avatar
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    Woody,

    I am going to a lake that is just 400 ft above sea level next weekend.

    I have been riding on a lake that is almost 1200 ft above this summer so far. What type of difference should I expect?

    Max rpm is 7080 at 1200ft and mph is 71.8mph (with tabs, 1200 grate, ect.)

  4. #4
    WATER WOODY's Avatar
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    Quote Originally Posted by Chrisrokc View Post
    Woody,

    I am going to a lake that is just 400 ft above sea level next weekend.

    I have been riding on a lake that is almost 1200 ft above this summer so far. What type of difference should I expect?

    Max rpm is 7080 at 1200ft and mph is 71.8mph (with tabs, 1200 grate, ect.)
    The weather will be a big factor Chris.First thing is to make sure you are not on the edge and have your fuel turned up before you ride.Then tune accordingly.Watch your tach close.

    If the air density is bad that day @ 400'.....you might not see any gains at all,might even see a loss.If the weather is good,and your dialed in,you might see a 40-60rpm gain maybe more.IT ALL DEPENDS ON YOUR WEATHER.

    I do hope to see you post some new speeds though.

  5. #5
    WATER WOODY's Avatar
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    Ive been wondering.............i hear salt water is faster,then i hear it is slower than fresh. Wonder what the difference is between CLEAN fresh water and MUDDY fresh water.
    Im just adding to the different variables between elevation and different water types.Hmmmmmmmmmmmmmmmm

  6. #6
    Chrisrokc's Avatar
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    Quote Originally Posted by WATER WOODY View Post
    The weather will be a big factor Chris.First thing is to make sure you are not on the edge and have your fuel turned up before you ride.Then tune accordingly.Watch your tach close.

    If the air density is bad that day @ 400'.....you might not see any gains at all,might even see a loss.If the weather is good,and your dialed in,you might see a 40-60rpm gain maybe more.IT ALL DEPENDS ON YOUR WEATHER.

    I do hope to see you post some new speeds though.
    Yea I plan to tune my EFI for down there also. Alread have my little screw driver in the glovebox

    Hopefully I will find some RXP's to roast

  7. #7
    WATER WOODY's Avatar
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    Have fun Chris,hope to see new #'s. Have fun at your RXP BBQ fest! Dont eat too much.

  8. #8
    All hail the Chief! fullboogie's Avatar
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    Woody has an excuse for everything. Quit yer whining and bring it to MB4 you pansy!

  9. #9
    WATER WOODY's Avatar
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    Quote Originally Posted by fullboogie View Post
    Woody has an excuse for everything. Quit yer whining and bring it to MB4 you pansy!

    MAN.my single piper would go soooooooo fast,it would even change YOUR signature Dave! heheehee I would be willing to give up a couple mph and hand it over to ya. Just because im a nice guy.

  10. #10
    Chris you should get in the habit of calculating the RAD (relative air density) every time you ride. It gives you a single number that combines the temp, altitude, dewpoint and baro.. For example, 2 weeks ago in tampa,even though we are at sea level, the RAD was 2717 feet above sea level because of stifling heat and humidity.... Elevation change can be nullified if the temp and baro and dewpoint are different also, which they usually are...Ross

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