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Part Three: The Transfer Ports

Discussion in 'Chainsaws' started by Mastermind, May 3, 2017.

  1. Mastermind

    Mastermind Leader Of The Clique Staff Member

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    OK.......so we've covered the exhaust port.

    http://opeforum.com/threads/part-one-the-exhaust-port.7279/

    And the intake port.

    http://opeforum.com/threads/part-two-the-intake-port.7290/

    Now let's talk about the transfer ports.

    We have two port engines, four port engines, boost ports, finger ports, bridge ports....bottom fed transfers, bore fed transfers......and transfers fed from the bottom front of the jug. We can open things up......or we can close it down.

    Crank stuffers should be talked about here.......as should case volumes.

    Who wants to kick things off?
     
  2. merc_man

    merc_man merc_man

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    Im in.

    This is going quickly.lol

    Sent from my SM-J320W8 using Tapatalk
     
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  3. Mastermind

    Mastermind Leader Of The Clique Staff Member

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    We can revisit the other threads at any time. I figure folks will bump them with questions and comments for a long time.
     
  4. David Young

    David Young Safety First !!!!!! Staff Member

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    I think we grind out a lot of engineered goodness the factory gave us in the name of flow. The first thing we all have done is open the hell out of the lowers. I think the best flow will be when the duct is even sized the whole way through.

    I believe the transfer design in the 346/357/372 and stihl 361 and the new echos are just about optimized. then they come out with the stratos and change the whole game.
     
  5. srcarr52

    srcarr52 We can't stop here, th1s is bat country!

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    I think a lot of compromises are made on factory transfer ports for the ease of casting and being able to maintain manufacturing tolerances.
     
  6. Stump Shot

    Stump Shot Old *pretty boy dipstick of Quality Staff Member

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    So is the timing number of the transfer opening critical to performance like I would think it is? Is the main thing to look for the difference between the transfers and the exhaust. Is there kind of a sweet spot to look for and try to achieve?
     
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  7. Mastermind

    Mastermind Leader Of The Clique Staff Member

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    In my humble opinion, there is nothing more important to performance than the relationship between the three ports that we are discussing.

    That means blowdown, and case compression time.
     
  8. David Young

    David Young Safety First !!!!!! Staff Member

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    what is the manufacturing benefit of the lip on the bottom of the lowers of just about every 2 port jug?
     
  9. Adirondackstihl

    Adirondackstihl Vert Da Furk........Bork Bork Bork

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    Here's a transfer question that might get kicked around....

    I'm currently rebuilding a 346 for a co-worker.
    All OEM.
    Question is, should I blend the lowers and cut the cylinder extensions to match the case or leave it alone? Why... Case volume?

    I'd port the whole cylinder if I had the tooling and knowledge.
     
  10. Moparmyway

    Moparmyway Its just a saw

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    If a picture is worth a thousand words.............................here are two pictures

    Is case volume or flow more important ?
    IMG_4131.JPG IMG_4130.JPG
     
  11. srcarr52

    srcarr52 We can't stop here, th1s is bat country!

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    It probably has to do with the interface between the core for the transfer tunnel with the core for the chamber and rough cylinder wall, to make the obtuse angle the core must get too thin.
     
  12. drf256

    drf256 Dr. Richard Cranium (“RC” to Muh pals)

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  13. Moparmyway

    Moparmyway Its just a saw

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    I dont think its of any benefit, more of a necessary evil for casting
     
  14. Mastermind

    Mastermind Leader Of The Clique Staff Member

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    Considering that at BTC flow would be negligible, is that really helping anything?

    Just asking for a counterpoint.
     
  15. Moparmyway

    Moparmyway Its just a saw

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    But that picture isnt just about flow now, is it ?
     
    Last edited: May 3, 2017
  16. Mastermind

    Mastermind Leader Of The Clique Staff Member

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    I'm not picking up what your putting down.

    Sadly I'm fairly thick and can't read between the lines. lol
     
  17. Moparmyway

    Moparmyway Its just a saw

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    To answer your question a little more directly (just a little) ......... is the benefit of trimming those sides more for dwell @ BDC, or for when the piston is approaching BDC ? ;)

    Also, that is a 346 cylinder ............... notice how the lowers arent hogged out to match the gasket/case ?

    So, I believe that they are both important in a work saw (flow and case volume) and should be considered together, depending on the intent. A race saw would benefit from opening up the lowers to match the gasket and the case, increasing case volume and decreasing velocity at the lowers
     
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  18. Mastermind

    Mastermind Leader Of The Clique Staff Member

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    I have no idea.
     
  19. Moparmyway

    Moparmyway Its just a saw

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    I believe that if the sides of the piston are left alone, they would protrude beyond the cylinder and tend to block the charge from getting into the lowers

    At least thats how my mind sees it
     
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  20. Mastermind

    Mastermind Leader Of The Clique Staff Member

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    Well it looks great. :)
     
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