Making a tuned pipe...SERIOUS POWER!

Discussion in 'Performance Mods' started by andyinchville1, Jul 29, 2007.

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  1. HI All,

    I am in the process of trying to make a tuned pipe for out 70CC engines.
    I am using a program that I downloaded that is supposed to give you all the
    crucial dimensions for the pipe itself BUT It asks for some measurements and information that I do not have or can get easily.
    I am hoping that the collective power of our brains can come up with all the info needed by the program so I can make a proper tuned pipe and report how well it works.

    Some of the information I will need is:

    1) The effective exhaust port diameter (mm).
    2) Diameter at the Barrel Flange ( I am not sure what this is actually) (mm)
    3) Length from the piston face to the flange
    4) The exhaust port opening angle (degree ATDC)
    5) Engine speed at max power (RPM)
    5A) Mid section Mean exhaust temp at Max Power (degrees C....need an
    infrared non-contact thermometer for this I guess)

    Other info that may be helpful is: (this is used in another program but I think the program I am using can make do with the items 1-5A above)

    6) Bore (mm)
    7) Stroke (mm)
    8) Connecting Rod Length
    9) H.P.
    10) exhaust port start opening angle (degree)
    11) Exhaust port full open angle (degree)

    If I can get all the needed info above I and a friend will begin the build ASAP and report our findings.

    Thanks in advance for any and all help....Looking forward to making
    some serious power (Hmmm we may soon be needing some sprockets in the 20T range before long!...HA)


  2. dave1490

    dave1490 Guest

    if it,s the expansion chamber design utility prog.youll see 2 design,s 1 for wide band and 1 for narrow band.enter the prameters as listed{use 1 design only}wide or narrow power pick wide band being{diffuser type 2.0,exhaust temp 500,diameter coefficients 2.125,tail pipe dia 0.7}for the barrel exhaust duct go to tools,then profiled exhaust port equ your numbers,lenth of piston face is the lenth of the piston skirt,exhaust port opening angel is between 70 and 105{i didnt know this because it has to do with port mapping so i used 87}max rpm came up with a 4ft pipe 2in in diameter for a 2 stage and 3in dia for a 3 stage with all the locations of the shapes and sizes needed.
    Last edited by a moderator: Jul 29, 2007
  3. HI,

    Yes, it is the program that was mentioned on another thread on this site....I would prefer to use this program instead of the design on the Traxxis (I think) site since this utility will do all the figuring for would be interesting
    to see if the two cone up with similar pipe designs tho...

    Just curious but how would one measure the connecting rod length? it the distance from the lower end of the piston wrist pin (on the rod itself) to the bottom of the connecting rod to where it meets the crankshaft?

  4. dave1490

    dave1490 Guest

    no, it,s from the center of the wrist pin to the center of the big realy need the right tools to do this kind of job,for example to find the port angel you need dial indicator to find tdc{top dead center}then you zero the degree wheel and turn the crank to just when the port open,s the number on the wheel will give you the degrees angel.not eveyone has thies tools.
  5. HI,

    Yes, I see what you mean...the proper tools in that case would be important...I mean to get the perfect distances of everything...Any idea how accurate the numbers need to be..I mean will a 3 or 4 mm one way or the other be too inaccurate?....I could probably measure better than that tho....A friend has a digital caliper accurate to the thousandth of an inch....I think the degree part would be the tough one for me ( I think I know what the tool looks like but don't know anybody that has one)....Are these specs available from somebody?...Who is the main importer of the 70 CC engines?...You think Duane at Dax would have these specs?...I may try him anyways.

    Thanks again.

  6. HI,

    Just a FYI, I spoke with Duane at Dax earlier today and he does not have the
    info we if any body else has an additional piece of the puzzle I'd love to hear from you!

  7. gone_fishin

    gone_fishin Guest

    as a planned project, i will be tearing one (dax 70) down to the sinew very soon to have a closer look.

    when i do, i'll let you know & you can run me thru the measurements you need. i'm sure i can be accurate enough for the task 8)
  8. Great!....I am looking forward to the measurements!....I may also try tearing my helpers old engine apart just to see what the insides are like (he wrecked his bike awhile back and has not ridden it since even tho he is pretty much fully recovered by now....I almost hate to take it apart for fear of not getting it back together properly...Oh well the things we do for performance! ;-O

  9. OldPete

    OldPete Guest


    Google images of degree wheel, print out a couple and bond them to stiff cardboard. I like using 10" or 12" dia. because the spacing between degrees fits a coat hanger wire pointer.
    Use a long reach spark plug as a positive stop to locate TDC. You know the drill, rotate the engine both ways till it stops then split the difference at the degree wheel.. Then DON'T bump the wheel or pointer once all is set.
  10. I hope this project takes shape and there is a real tuned pipe for these in the future.

    andyinchville1, If all goes as planned I may be in your area this weekend.
  11. Hey Just for kicks,

    Where abouts in MI are you from?...I have relatives there (Clinton Township)....Are you stopping in Charlottesville or just passing through?..If you're here for a bit bring a degree wheel and we can start this pipe...HA...OK I have to ask....Are your riding your bike through here?...Go for the long distance record!

  12. I'm not far from clinton township, I'm in pontiac.

    We'd be in the blazer and it's looking like it would be a long trip in that so the bike will be at home:(.

    I hope to purchase something that is about due north of you and if it works out I'll be stopping just long enough to pick it up and then drive the wife out to see the ocean, she's never seen an ocean.:)

    How long does it take to drive to michigan from there? I'm guessing between 7-10 hours.
  13. gone_fishin

    gone_fishin Guest

    ok, here's the deal...

    i'm but a few days away from having my lab-engine available for tear-down.

    someone's gonna have to define the dimensions needed, and the method of measurement, in very simple layman's terms.

    just give me a simple one-by-one list, and i'll do my best. KISS (if you don't know what that means, you're not stoopid enuff yet)

    ps-the engine will be a dax 70
  14. HI,

    Ohhh....I can hardly wait....I assume you have some calipers to do the measuring?..I don;t know how to read them so I cheated and bought some calipers with a digital readout!....As far as guiding you through the # needed I would be happy to try to help you with that...I am not necessarily an expert on this either but I do have a general / vague knowledge and what I don't know, A friend down the street runs an auto repair shop so I'm sure he could help. One of the crucial things we will need are the precise figures (in degrees) for the opening and closing of the exhaust ports because...this may be actually the most important figures to have so a degree wheel is a must),....Getting the #'s is hard to describe but I would be happy to try to talk you through it....My Cell # is 434-760-6924...Let me know when you want to try to get the #' best / most free time is Sundays (usually early afternoon).

  15. Oops...I almost forgot...I am still waiting for my helper to bring his old engine back so maybe I can double check and try to get some #'s too....Very important to have accurate #''s for an optimum pipe....anything that is too far off (I'm not 100% sure of the allowable tolerances) will negate potential benefits of a tuned pipe because the pressure waves literally have mere milliseconds to "supercharge" the engine when the engine is at speed...

  16. gone_fishin

    gone_fishin Guest

    i'm educated in mechanical drafting, way back when you had to sharpen your own lead...i know a bit about determining angles & i'm adept at accuracy.

    what i'll need is "set the piston to exactly here on the port" or "measure from here to here" kind of directions.

    i'll let you know when i'm ready...if you'd like, you could start posting the set of needed dimensions in 1, 2, 3 fashion, maybe others would like to have the parameters anyway, so they can have a look at their own engine.
  17. gone_fishin

    gone_fishin Guest

    i'm ready whenever you are.
  18. Hey all,

    Sorry for not getting here sooner (lost the thread)....Hope you had a good trip....I meant to tell you it takes us 12 hrs to Detroit vicinity from Charlottesville (stops for food & breaks etc adds time)....

    Augi, I started measuring the innards of my helpers disassembled engine....Love to compare #'s tho in case his engine is far out of spec....could average our numbers....I'll write back soon since I will be busy with work the next day or so
    (haven;t won the lottery yet so still ave to grind out some long days!)...