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Thread: ESE's works engine tuner

  1. #34336
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    25th March 2004 - 17:22
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    That's a lot of balls in the air, and presumably I assume Av vs unleaded skews the pitch rich to advance
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  2. #34337
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    13th April 2009 - 22:30
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    Quote Originally Posted by wobbly View Post
    You are not paid to think
    Am I getting paid? News to me.

    Thanks for the reply, exactly what I wanted. I'll see if I can put it into practice this weekend.
    ........Rules are for fools and a guide for the wise ..............

    http://www.marshland.co.nz

  3. #34338
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    13th December 2018 - 18:06
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    Great stuff
    Also, those sheet metal cutters from this or the last century are not half bad.

  4. #34339
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    18th May 2007 - 20:23
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    If not "Genius" then incredibly clever and very interesting two stroke project. Impressive work.

  5. #34340
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  6. #34341
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    18th March 2012 - 08:35
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    Blah If easy isn´t worth anything....

    Alex, you should take contact with Mahle and make their blend of nicasil ingredients official, That´s a hard task for you

    Going the easy way with a steel liner is like the opposite of your new t-shirts

  7. #34342
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    25th March 2004 - 17:22
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    Needs a cylinder leak test rig. We've covered them about 300 pages ago. Lock the crank with piston above top of ex. That should tell what the seal is really like.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  8. #34343
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    20th April 2011 - 08:45
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    Quote Originally Posted by F5 Dave View Post
    Needs a cylinder leak test rig. We've covered them about 300 pages ago. Lock the crank with piston above top of ex. That should tell what the seal is really like.
    Something like this Dave?
    Click image for larger version. 

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    You could lock the crank in any position if you so desire, but it might be instructive to 'scan' the cylinder by holding the piston in a number of positions with a long ring spanner on the crankshaft nut. That way you can establish the point of maximum wear.
    I also used this method to check whether the piston ring was stuck in its groove, and if so, on what side of the piston, without even opening the engine.
    If the ring is stuck, lifting the piston away from the bore because of the inclined con rod angle will also lift the ring off the bore, aggravating the leakage.

  9. #34344
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    8th December 2014 - 14:39
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    Hi all
    My questions are concerning the 'T' shaped, vertical bridged, exhaust port used in some engines, one being the Yamaha YZ125. I believe it was Woobly said with this type of ex port to reduce the area at 1.5 x the bore in the exhaust duct, to only 95% of port area at the bore. My first question is does this still hold? My second is how far down the duct should you blend the 'T' shape into the main stream?
    Most of the cylinders I've seen, they've ended it less than half way down the duct. I understand the exhaust wall is fairly thin in some cylinders so another question is can you curve this blending process to try to extend it down the duct? Thank you for any replies. Jeff

  10. #34345
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    8th February 2007 - 20:42
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    The T port engines respond exactly the same as 3 port , both have large blowdown capability , and need all the help available to keep the velocity up as the piston is lowering from EPO.
    In most cases the smallest area should be at the duct exit , the face where the manifold fits on.
    A couple of engines I have done have a female spigot as part of the cylinder , in this case I have made a new spigot that presses into that female step , and then forms a new male slip fit for the header to attach to.
    The exit area should be 75% of the EFFECTIVE area of the port at the bore - that is the chordal area X the cosine of the duct roof down angle.
    In a full noise T port duct the exit should be oval - with the width at the same size as the header diameter.
    This means you end up with an ellipse of 42 wide by 31 high if its like an A kit Honda performance capability.
    Then the spigot has a transition from this oval shape out to the round header.
    The spigot should have its floor colinear with the duct exit angle , and all of the transition angle is done in the roof - this means lifting the header exit centerline some 3mm above
    the center of the cylinder duct exit shape.
    No steps anywhere - some have reported that steps help mid range power off corners , but if the spigot is lifted then that setup has the same mid power as the steps , but way more top end.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  11. #34346
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    13th December 2018 - 18:06
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    I, thinking there should be a duct exit/min area factor of the blow down area, as opposed to the effective ex area. Is there such a formula?
    And why is it the chord area and not the curved?

  12. #34347
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    You are right - as Frits has pointed out a couple of times , the duct exit area should be tied to the Blowdown STA .
    This would be technically correct , but the 75% area guide idea was derived from a huge number of race engine projects finalised in EngMod.
    The exit area is tied in fact to the gas speed Mach number , as it turned out virtually all the engines I have done made best power with the duct exit Mach at 0.8 , and this was virtually always seen
    with a 75% area ratio or very close to it.

    The chordal area is that actually presented to the gas flow , the curved ( arc ) width has no influence whatsoever on the gas flow Mach number or the Cd thru a duct.
    You can have say a 40mm Exhaust chordal width port on a 54mm bore or a 70mm bore. The effective duct area will be identical in both cases , but the 70mm bore will have less arc length across that chordal 40mm.
    Thus arc widths are of no use at all in port calculations , to establish angle area or STA.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  13. #34348
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    13th December 2018 - 18:06
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    Quote Originally Posted by wobbly View Post
    You are right - as Frits has pointed out a couple of times , the duct exit area should be tied to the Blowdown STA .
    This would be technically correct , but the 75% area guide idea was derived from a huge number of race engine projects finalised in EngMod.
    The exit area is tied in fact to the gas speed Mach number , as it turned out virtually all the engines I have done made best power with the duct exit Mach at 0.8 , and this was virtually always seen
    with a 75% area ratio or very close to it.

    The chordal area is that actually presented to the gas flow , the curved ( arc ) width has no influence whatsoever on the gas flow Mach number or the Cd thru a duct.
    You can have say a 40mm Exhaust chordal width port on a 54mm bore or a 70mm bore. The effective duct area will be identical in both cases , but the 70mm bore will have less arc length across that chordal 40mm.
    Thus arc widths are of no use at all in port calculations , to establish angle area or STA.
    Thanks Wobbly, The port window as is curved is not fed only from one angle, it would see gas flow from the partial circle between the cord and cylinder wall above also?

  14. #34349
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    25th March 2004 - 17:22
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    Pressure will be equal inside the cylinder, and high pressure at that. It can only squeeze out one port.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  15. #34350
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    4th December 2011 - 22:52
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    Quote Originally Posted by andreas View Post
    Thanks Wobbly, The port window as is curved is not fed only from one angle, it would see gas flow from the partial circle between the cord and cylinder wall above also?
    Yes, the calculation for the flow area in a T-port takes into account the side wall angles.

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