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  1. #1
    Chrisrokc's Avatar
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    When to up-pitch from 14/20

    I am running a 14/20 Dynafly as many of you know. I have finally "unlocked" my ski thanks to many on this bored. I am turning over 7100 rpms. 7145 rpms to be exact at 72+ mph now. I know this is where i want to be.

    My question is when is a good time to up-pitch the impeller RPM wise? I have been thinking about doing another big round of mods in a month or so but thought, well I might have to repitch. The mods I plan to do are

    Sonic Boom TBs (maybe big bore ones if they make more power)
    Lowell Milled Stock Head (going from 118 psi in the heat to 140-155psi)
    Advent ECU if it really comes out any time soon if not... maybe keyway.


  2. #2
    All hail the Chief! fullboogie's Avatar
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    Since you are only running a little over 7100 rpm's in the heat, I'd leave the prop alone. If you pitch higher, you're going to pull the rpm's down way too far.

    Wait to see what the mods do for you, rpm-wise, then go from there.

  3. #3
    Chrisrokc's Avatar
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    Quote Originally Posted by fullboogie View Post
    Since you are only running a little over 7100 rpm's in the heat, I'd leave the prop alone. If you pitch higher, you're going to pull the rpm's down way too far.

    Wait to see what the mods do for you, rpm-wise, then go from there.
    Well thats what I mean. If I run 7145 in the heat now and I add Sonic booms I will be 7255-7225rpms. Then head will help me turn things and the ecu will surely give me a bump. Lets say said and done 7300.

    My question is what rpms are you guys repitching the 14/20?

  4. #4
    My son (mohawk man) jeffsntx's Avatar
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    Quote Originally Posted by Chrisrokc View Post
    My question is what rpms are you guys repitching the 14/20?

    Chris, you are kind of asking an open ended question. Since everyones pitching techniques are a little different, you will get 100 different answers.

  5. #5
    Chrisrokc's Avatar
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    Ahhh, well I mean since the target rpm is 7150 and lets say I was running 7300 what type of pitch would I want. Or is that also too open ended? If so man this stuff is confusing lol.

  6. #6
    WE DONT DIAL 911 RDH's Avatar
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    Quote Originally Posted by Chrisrokc View Post
    Ahhh, well I mean since the target rpm is 7150 and lets say I was running 7300 what type of pitch would I want. Or is that also too open ended? If so man this stuff is confusing lol.

    trial and error...

  7. #7
    My son (mohawk man) jeffsntx's Avatar
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    Quote Originally Posted by Chrisrokc View Post
    Ahhh, well I mean since the target rpm is 7150 and lets say I was running 7300 what type of pitch would I want. Or is that also too open ended? If so man this stuff is confusing lol.
    Chris, as long as you have the same person pitching it every time I guess you could tell them that you at XXX RPM over your target and they should be able to correct it for you. If you send it to 2 different people you will get 2 totally different results. This is basicly the same thing that Ross was talking about not too long ago.

  8. #8
    Nothin' runs like a Deere IowanGPR's Avatar
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    So if I am at 7400 RPM's and want to lower them... I can tell Carl and he will repitch what he thinks will correct my RPMs to 7150 ? i am running 7400 in 90* heat. ... about 71.8 average speed i think i can hit 75 next spring after some fine tuning/truing, and modding...

  9. #9
    Moderator RX951's Avatar
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    Wait till you bolt on the Sonic Boom's and go from there.
    Or basically wait till you add more mods...compression, booms, ect..... for now, I'd keep her right there.

  10. #10
    My son (mohawk man) jeffsntx's Avatar
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    Quote Originally Posted by IowanGPR View Post
    So if I am at 7400 RPM's and want to lower them... I can tell Carl and he will repitch what he thinks will correct my RPMs to 7150 ? i am running 7400 in 90* heat. ... about 71.8 average speed i think i can hit 75 next spring after some fine tuning/truing, and modding...

    7400???? If you are turning that much on a single pipe in heat, you DEFINATELY need someone to do some bending. If the prop originally came from Carl, I would bet that he can get you real close.

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