porting

Discussion in '2 smokers' started by willis 2000, Jul 21, 2012.

  1. Twin-shocker

    Twin-shocker Long timer

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    Polished ports seem to work effectively in parting customers from quite large amounts of money, but do serve as a very good indicator to help avoid anyone suggesting this improves a motor in any way!
    #21
  2. supershaft

    supershaft because I can

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    When I was a kid we didn't have a flow bench but we did have a dyno. Maybe there isn't much difference between a mirror finished exhaust port and a mirror finished export that has been ruffed up by a bead blaster. I have never done that test. But I do know that a mirror finished export over most stock finishes makes a big diff and keeping it spotless makes all the difference. The exhaust port sees most everything twice and therein is the difference IMO. That and flowing exhaust very well might not show the advantage for everything going on in them velocity wise. The other ports don't deal with sonic and supersonic. You can't reproduce that with a flow bench.

    Of course a good pipe over a crappy one will make a huge difference but that is beside the point.
    #22
  3. Twin-shocker

    Twin-shocker Long timer

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    Sadly even if the polished exhaust ports do make a big difference on the dyno, I wonder if this is really worth the effort as carbon will build up pretty quickly on anything other than a race motor which gets stripped very regularly, and the polished finish will then be gone?
    #23
  4. anotherguy

    anotherguy unsympathetic

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    Ever heard of a pitot tube? W/O using Google?

    When does an exhaust port go trans sonic? Please show your work.
    #24
  5. Twin-shocker

    Twin-shocker Long timer

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    Maybe the mirror finish port guy is someone ripping off gullible customers with this type of work? After all shine is much much easier than doing a job that might actually work.
    #25
  6. supershaft

    supershaft because I can

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    Putting you engine at TDC and taking off a pipe to clean up you exhaust port is easy.

    No gullible customers involved with my findings. Just a couple of guys racing for our shop back the seventies.

    Trans sonic? Explosions have trans sonic pressure waves. What do you think pushes a bullet to trans sonic speeds? But let's just stay with sonic for now. A flow bench can't duplicate that either. Surely you must understand that flowing exhaust is much further from what actually goes on in there in a running engine than flowing intake.

    I don't know about new bikes but back in the seventies a good port job made all the difference in the world. Granted, most of them weren't good but that is beside the point.
    #26
  7. willis 2000

    willis 2000 neo-quixote

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    Yes, I was talking about the old stuff, before it was possible to translate design to production easily.
    I didn't find it necessary to alter port timing to get large gains of low-to-mid power.
    It is also unwise to attempt to make race bike power from an enduro-style engine. But these can have fabulous, usable powerbands when set up properly.
    Did anyone else mess with case reed intakes? I worked over a slug of an RM250's intake tract, it seemed like the case passage was an afterthought, advertising hype, or maybe it was difficult to cast. I made the case passage much larger, man, that bike made everyone jump back the first time it was started. It had a new bark from before, never did rev high, but the torque made it a real competitor.
    I think it's about making the best of what you have.
    #27
  8. Twin-shocker

    Twin-shocker Long timer

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    In regard to making the type of alterations to porting that seem popular in the world of those who charge top dollar for a polished finish, I wonder as it seems these guys know better than those who manufactured the bikes, why they arent working for the factories rather than offering 25-50% power increases to customers through crude hack jobs and polishing?
    #28
  9. anotherguy

    anotherguy unsympathetic

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    First of all you failed to answer my query. Try that first. When does the burning (hint hint) charge go trans sonic? Please show the math.

    Now please tell me when the fuel/air charge explodes. Your failure to comprehend the events inside an engine is staggering for someone who claims so much.

    Do yourself a favor and read and understand some Vannick,Mike Chapman or maybe Heywood before you enter into a discussion about combustion. At this point you're so absolutely clueless it's a waste of bandwidth. Nothing like a battle of wits with a buffoon.
    #29
  10. Strong Bad

    Strong Bad n00balicious

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    Hubristic theory is one thing, horsepower to the ground and being able to manipulate the power band where you want it is a completely different matter. NONE of the greatest 2 stroke motocross tuners of the 70's had anything more than a high school diploma. Back in the day, we not only gave riders more horsepower, we gave them horse power their riding ability could use. Donnie Emler's FMF had a great advantage in his first shop with the dirt road and lot next to the shop. He learned how to develop real world horsepower that would win on the track, not set speed records on Bonneville Salt Flats. Back in the 70's the speed shops who did well were the ones that realized that not all of their customers could used mega HP with a very narrow powerband the pros could ride. Their services matched both the pipe and the porting to the rider's ability.

    Hard to lower the exhaust port bringing the powerband down into a lower rpm. The Power Valve that came in the 80's did exactly that, it allowed for a variable exhaust port timing. Increasing bottom end is easier done with a longer headpipe and/or center section with the pipe. Increasing the volume in your intake is what killed your torque.
    #30
  11. anotherguy

    anotherguy unsympathetic

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    Hubristic theory? Please. Setting the squish and flame front travel is elementary tuning. As is installing a good pipe (uhm FMF??).I am talking about simple effective tuning methods available to everyone.

    Lack of education doesn't make what Emler and his contemporaries did less sophisticated. You must admit designing a good exhaust with pencil and paper does require some advanced knowledge of what goes on inside. And more than a little advanced mathematics.

    I simply called out an obvious charlatan. Hubris has nothing to do with that.
    #31
  12. supershaft

    supershaft because I can

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    Well, willus, Strong Bad and I could have a good discussion with this if it weren't for blow hards. Empirical data on the idiotnet? With pictures! :rofl
    #32
  13. Strong Bad

    Strong Bad n00balicious

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    Attempting to beat down a guy on the interweb in your manor is hubristic at best.

    I'm telling the was it was with some of THE most successful 2 stroke tuners of the 70's & early 80's as seen from someone that was on the inside and intimately involved. Seat of the pants and hours and hours of trial and error is what happened. No pencils and no math, lots of; "what if we"? I bet none of them, even to this day, would know what a Reynolds Number represents.

    Setting squish for some reason is a more recent concern, back in the 70's squish was only checked after a head was modified. Aftermarket heads were sold by the 1000's and the consumers were never told to (or how to) check the squish with the new head. I did hundreds of port jobs for EC Birt & Donnie in the 70's where the heads were not modified and squish was never addressed. That is simply the way it was AND it worked!
    #33
  14. Icewalker

    Icewalker Conundrum

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    Interesting thread. I can't speak much for the bike world since almost all of my two stroke experience was in the world of European Karting. One thing I do remember though is that every once in a while someone would get a bone stock motor from the factory (usually a Parilla or DAP) and it would be as fast if not (in at least one case) faster than any of the ported motors out there.

    I can't explain why - anyone want to take a stab at it?
    #34
  15. Ever Onward

    Ever Onward Older,Wiser, Smarter

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    Uhhhhh Ohhhhhh...............



    [​IMG]





    Not only has the infamous Yamaha Power valve entered the equation........but, my TZR has shaved head which altered the squish, and cleaned up transfers.......I have no idea how it even runs now ? :lol3

    If I polish all the ports to a mirror finish do I have a shot at a trophy on "bike night ?" :rofl





    [​IMG]
    #35
  16. willis 2000

    willis 2000 neo-quixote

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    I appreciate the differing points of view. Kinda like mechanics bench-racing. That squish angle/clearance/area was a part of the picture I was unaware of.
    #36
  17. anotherguy

    anotherguy unsympathetic

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    I'm upset that someone doesn't like my manor. I always thought it was quite nice.

    [​IMG]




    now that's hubris............

    #37
  18. Abdelhub

    Abdelhub Blanco Trasho

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    so is it ok to raise my exhaust port height by a mm???? time to get out my dremel.....

    Mike
    #38
  19. supershaft

    supershaft because I can

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    Differing points of view are great. It's the character slamming/name calling that is nothing but a waste of time here on the idiotnet. That crap is better left for meetings in person IF it is to be brought up at all.

    Compression/squish angle was always in the cards around my dad's shop. They experimented with it quite a bit if I remember right. When I was real little I think they even tried running alcohol but that was a little before my time I believe.
    #39
  20. supershaft

    supershaft because I can

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    Typically, raising the exhaust port is the last thing I would try. High rpm power? First you have to GET to high rpm!
    #40