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Thread: Tuned length table

  1. #1
    modifiedoutboard OUTBOARDER's Avatar
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    Default Tuned length table

    Figuerd it out finally
    Attached Images Attached Images  
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

  2. #2
    Sam Cullis Mark75H's Avatar
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    Very nice.

    I do not understand what the ft/cycle in/cycle relate to. Are they sound? At what temperature?
    Since 1925, about 150 different racing outboards have been made.


  3. #3
    modifiedoutboard OUTBOARDER's Avatar
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    Default 600 Mph is used

    Quote Originally Posted by Mark75H View Post
    Very nice.

    I do not understand what the ft/cycle in/cycle relate to. Are they sound? At what temperature?
    600 mph is used for avg wave velocity bouncing in and out thru stack, carb, venture and reeds @ sea level.

    1Cycle is 1 rotation, inches wave travels during 1 Rev of engine is inches/cycle times avg speed. To get 3rd overtone divide by six.
    The guys with the six second kawi two-stroke bikes tune for second wave or divide by 4 .

    Because reeds stay open or closed for a while there is also a effective range of about 1,200 rpm .
    Last edited by OUTBOARDER; 12-18-2011 at 11:59 PM. Reason: finie
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

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    Where does the exhaust port duration come into this calculation?

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    And it HAS to!

    Jeff

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    modifiedoutboard OUTBOARDER's Avatar
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    Default Looper

    Quote Originally Posted by Fastjeff57 View Post
    And it HAS to!

    Jeff
    This is for a reed or rotary valve LOOPER , exhaust waves do affect crankkcase pressure but is NEGLIGIBLE for calcing intake side tuned length.

    The table results are the same as the TSR program used by many.

    Talked with him about theory and he was one of the first to put known formulas to software for racers.
    His Yamaha RD400 Twin held quarter record 9.37@143mph for over a decade.
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

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    Sorry my mistake as it looked like you were calculating the exhaust tuner length for a 3 cylinder motor with an equal length 3 into 1 tuner.
    I wasn't aware you could apply Helmholtz to reeds, I though it only worked on piston & rotary ported motors, oops, back to reading the books.

  8. #8
    modifiedoutboard OUTBOARDER's Avatar
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    Default 3:1 pipe from KAWI 900 STX TRIPLE

    Quote Originally Posted by Seagull 170 View Post
    Sorry my mistake as it looked like you were calculating the tuner length for a 3 cylinder motor with an equal length 3 into 1 tuner.
    I wasn't aware you could apply Helmholtz to reeds, I though it only worked on piston & rotary ported motors, oops, back to reading the books.
    We will be testing a couple of 3:1 exhaust chambers on a 49 ci OMC in the near future.
    Will use sst60 test wheel to compare.

    PWC TRIPS picked up 15 Hp from the pipe.
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

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    They Want it cheap..............

  9. #9
    Team Member hupiveneilija's Avatar
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    Quote Originally Posted by OUTBOARDER View Post
    Figuerd it out finally
    Old thread, but is that "3rd wawe number" inches from reed tip to intakes outer edge?

    Thanks, Jani

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