exhaust port

Discussion in 'Maxiscooter Tuning' started by dylanbws100, Nov 16, 2008.

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  1. dylanbws100

    dylanbws100 New Member

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    147
    Hey folks.....
    well I put the performance pipe that I had back on....was first registering 8 200 to 8400 RPM on a flat....but now with the pipe it does 9000-9100.
    But the question that got raised in my head when I was putting it on is this:

    The exhaust port measures (on the flange side) 21mm........the exhaust is 29mm............but the max width of the flange is 31mm....so that means if I open it up to 28mm....it'll only have 1.4mm each ide of the exhaust.....
    Not good.

    So are there gains to be made in taking the risk?
     
    dylanbws100, Nov 16, 2008
    #1
  2. seanwhite06

    seanwhite06 New Member

    Messages:
    358
    Rides:
    runner 172, zx6r
    i would say match away but thats a VERY small clearence!
    what barrel is it and what pipe isit? got any pics?
    gains would be very worthwhile though.
    could always get extra material welded on for extra support!
     
    seanwhite06, Nov 16, 2008
    #2
  3. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    I tried editingthe post that started this thread, but it looks like it didn't save them....Here are the dimensions
    exhaust: 28mm
    exhaust port (currently) 21mm
    max width :31mm.....but that was measured on the OUTSIDE of the flange (on the thinnest part)...

    It's a standard 100cc nitro engine....was gana raise the exhaust 1mm and widen it 1mm each side, but I'll do everything in one go....

    I'll upload some pictures of the exhaust tonight....(4 hours about)

    Maybe I should just make it 25mm....that way there will be 2mm on each side.....any gains in that?

    oh just BTW.........what gains does this mod offer anyway? is it more RPM as the gasses can exit faster?
     
    dylanbws100, Nov 16, 2008
    #3
  4. seanwhite06

    seanwhite06 New Member

    Messages:
    358
    Rides:
    runner 172, zx6r
    yes it should give a healthy gain in rpm as the engine can breath more freely,

    i dont know your std port map but yer widen the port, take it out to the full 68% if the barrel allows.

    what timings will you then have with the 1mm raise?
     
    seanwhite06, Nov 16, 2008
    #4
  5. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    Hey man........Before I post this....nobody rip on me alright? If you thinking about it...then don't read on!

    I've been speaking to my mate in Netherlands.....Very much respected tuner, goes by the name of Bram Steenhoek. Anyway, he has tuned for years, and gave me those dimensions to port to....Being 1mm higher and 1mm either side. So I wouldn't know what the timings will come to. I'll have to measure it when I strip it.

    My question back to you is this.......
    What is the 68% of bore that everyone speaks of...

    the way I understand it is if the standard bore is 52mm....then 68% of that is 35,36..........much bigger than maximum tolerance. Please explain?

    Thanks,
    Dyl
     
    dylanbws100, Nov 16, 2008
    #5
  6. alperin

    alperin Active Member

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    1,621
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    aerox 180cc
    i am confused :D wat world are we living in lol
     
    alperin, Nov 16, 2008
    #6
  7. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

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    14,276
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    et2 monster
    the width is incorrect... a 1mm raise and 1mm each side ius a GENERAL thing to try.. and keep trying till it makes it worse.. thenm you have figured out the map.. simply 1mm on ANY barrel prittymuch will make for more power and a narrower powerband.
    68% is a gewneral rule, yet ive gone up to 46% of the barrel wall...

    if you look a 172 port is technically to its max width, altho i can do them twice as wide.. all GENERAL rules really m8 and nothing you cant lift out of any tunning book, rules are there to keep it safe, within tollerance and keep heat/fuel consumption down.. if your in a wacky mood and dont mind it lasting 5 mins you can break these rules.. like my evo port on an iron 50 (with no devider) ye munched the rings quicktime but those 14 miles were fun as fuck!! (once i got the thing setup of course)
     
    MiNoR cOnFuSiOn, Nov 16, 2008
    #7
  8. Dec

    Dec Active Member

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    3,183
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    nothing ugm
    your a fuckin loonatic LOL evo port map on a 50 :w00t:
     
    Dec, Nov 16, 2008
    #8
  9. Crana

    Crana Active Member

    Messages:
    1,056
    14 miles :D Fun pushing it home? You're crazy ;p
     
    Crana, Nov 16, 2008
    #9
  10. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    haha...interesting :)

    But my question still remains.....what is this % of bore that everyone speaks of?

    And yeah, I agree with the rules bit...makes much sense. Thanks :tup:
     
    dylanbws100, Nov 17, 2008
    #10
  11. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

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    14,276
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    et2 monster
    erm, m8.. dont bother with it.. you cant figure that out you dont wanna be messin wiht barrels just yet


    a % of the bore is basicly the ammount of the circumfrence you can cut out of any port so the rings stay in place.. better rings mean you can go wider but it will always wear v quickly at larger %
     
    MiNoR cOnFuSiOn, Nov 17, 2008
    #11
  12. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    haaa....so it's the % of the bore...which can be taken from the widthe of the bore right?
    So what about bridged ports? doesn't it count then?
    And yeah, i said don't rip on me about the topic. This is why I'm asking, so I don't syuff it up. Everyone has to start somewhere.
    Cheers mate
     
    dylanbws100, Nov 17, 2008
    #12
  13. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

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    14,276
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    et2 monster
    the width of the piston is the active size..

    basicly you map your port (trace the map from the barrel) then messure the circumfrence of the piston (again wrap paper round and mark) now a figure of the circumfrance (when laid flat) can be cut into the exhaust port (again when laid flat so cut the map then put back in the barrel an mark it up from that template) to get this figure you need to work out the percentage difference between the diameter and circumfrence then devide by 60%... bit long winded really
    a bridged port means you have 2 so can go to neerly half the circumfrance of the piston.


    easy way is just the diameter of the the piston, minus 40%.. cut a match stick that length, centre on the exhaust port and even on the piston then mark the ends of the matchstick...

    do yourself a fav.. dont go by what people tell you.. read up and LEARN the mathamatics behind porting BEFOR you try it out.. its not just cut here ye 60% is always good blah blah.. theres ALOT to it and a couple days wiht your head in a decent book will clear everything up for ya
     
    MiNoR cOnFuSiOn, Nov 19, 2008
    #13
  14. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    Ok so hold on....

    if the bore is 52mm....* that by pi...

    52 * pi = 163.362818
    then

    (163.362818 / 100) * 60 = 98.0176908
    so that figure of 98.02 is the length in mm of the exhaust port? seems kinda long doesn't it?

    And if it's correct, after beveling the edges so that the rings don't snag...How many miles will this be good for?

    I take anything that is widened greater than stock will be benefitial.
    Even if I take it to 50 % of bore?
     
    dylanbws100, Nov 19, 2008
    #14
  15. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    Ok so hold on....

    if the bore is 52mm....* that by pi...

    52 * pi = 163.362818
    then

    (163.362818 / 100) * 60 = 98.0176908
    so that figure of 98.02 is the length in mm of the exhaust port? seems kinda long doesn't it?

    And if it's correct, after beveling the edges so that the rings don't snag...How many miles will this be good for?

    I take anything that is widened greater than stock will be benefitial.
    Even if I take it to 50 % of bore?
     
    dylanbws100, Nov 19, 2008
    #15
  16. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    Ok so hold on....

    if the bore is 52mm....* that by pi...

    52 * pi = 163.362818
    then

    (163.362818 / 100) * 60 = 98.0176908
    so that figure of 98.02 is the length in mm of the exhaust port? seems kinda long doesn't it?

    And if it's correct, after beveling the edges so that the rings don't snag...How many miles will this be good for?

    I take anything that is widened greater than stock will be benefitial.
    Even if I take it to 50 % of bore?
     
    dylanbws100, Nov 19, 2008
    #16
  17. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

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    14,276
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    et2 monster
    m8, i could sit here typing for days.. or you could just go buy a book...

    just stick with a 5% increase in width and a 1mm raisde wehile retaning blowdown timing...

    your NOT gonna learn everything you should know by askin on here.. grab a book, your more than capable quite obviously ;)
     
    MiNoR cOnFuSiOn, Nov 19, 2008
    #17
  18. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    Hope thats not sarcasm :emb:

    But to everyone that posted on the topic-thanks. Clarified a few things for me :beer:
     
    dylanbws100, Nov 19, 2008
    #18
  19. MiNoR cOnFuSiOn

    MiNoR cOnFuSiOn Administrator Staff Member

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    14,276
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    et2 monster
    not even a hint of scarcasim m8... obviously getting your head round it and can do maths.. grab a book, will have the theory down in a couple hours.. then its a case of actually grinding where you want to wiht the tool.. aint just knowing what your doing, its the ability to do it people often underestimate.. dremmels aint easy to use especially in small places
     
    MiNoR cOnFuSiOn, Nov 19, 2008
    #19
  20. dylanbws100

    dylanbws100 New Member

    Messages:
    147
    Yeah i hear it can be tough....Dads an engineer so sure I can get some help from him.
    And thanks for the compliment man....Nice to get good feedback from good tuners!
     
    dylanbws100, Nov 19, 2008
    #20
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