Expansion chamber , but needs research & development

Discussion in '2-Stroke Engines' started by djase10, Oct 26, 2008.

  1. djase10

    djase10 Guest

    Hi All
    Now that i have my Gasless MIG welder,
    i can weld thin steel
    without the worry of BLOWING HOLES through the work!!

    Time for what i have wanted to do for AGES ..

    Develop a cost effective expansion chamber..


    Bought a cheap pocket bike expansion chamber,
    & cut it up,
    & welded it together so to fit a HT 48cc..

    Results are ..
    without muffler ==TOO Loud , bottom end power increase ONLY,
    LOST top end power ..
    with muffler
    What a beautiful sound it has, it almost sounds like a 4 stroke thumper.
    lovely exhaust note, louder , but not Aggressively loud..

    sounds & looks the part ..

    BUT, as before

    So------- some further research & development is required..
    A pleasure to do ..

    Yes i could have bought a BETTER pipe to start with, but $75 JUST to cut up and see what happens isnt in my book..

    Only cost me $10. for the pipe i used..


    Attached Files:

  2. Mountainman

    Mountainman Active Member

    nice job of fitting and welding there

    with your slight loss of power -- guess the dimensions are off a little ?

    there is some good information floating around -- you are getting it -- NICE WORK

    ride that MB thing
  3. hill climber

    hill climber Member

    is that a stock plug wire and boot? change that for good parts and you may be surprised and get some more top end. if nothing eelse it should run smoother
  4. fastboy9

    fastboy9 Member

    your header pipe determines where abouts the power band is, at the moment it sounds like yours is pretty low in the rev range. This is because your header pipe is long, the shorter the header pipe (the pipe before the expansion chamber) the higher the power band will be, i.e. more top end. The longer the header, the more low end power.

    Its just all about getting the right measurements, to experiment I used some silicone tubing and hose clamps for a header, then adjusted this length until I got what I wanted.

    There is a good software program that you can download for free, that does all the dimension calculations for you: http://www.bevenyoung.com.au/mota.htm

    Hope this helps!

    AndyInchVille on this forum has designed and developed a pipe, maybe you should try talking to him?

  5. QuadManiac

    QuadManiac Member

    Neat program, but have any idea what most of the parameter values (port diameter, etc) would be for the standard HT engines, so we can get a start without tearing it down and measuring?
  6. djase10

    djase10 Guest

    Bottom end acceleration ehaust pipe:)

    Hi All

    RESEARCH & DEVELOPMENT can be a tedious and laborious process ,
    Also results can be achieved instantly & by accident ..

    The result of the pictured pipe is GREAT for bottom end performance !!

    I extended the pipe with an OLD SEAT POST of all things, TACKED them in place & then
    tested it rigorously last night ,

    WOW ..!!
    = dramatic acceleration curve ..

    with a 44 Tooth sprocket, it is SIMPLY fantastic at bottom / & MID end PUSH.

    TOP SPEED was in turn reduced to 45km/h,

    BUT that was of no concern BECAUSE it felt QUICK...

    SO , i will leave this expansion chamber AS IS ,
    ( welds / fractures tidied up first, to fix some cracks that developed during testing),
    and Hang it up to be used accordingly..

    This story will continue....

    Ride Safe ALL..


    Attached Files:

  7. QuadManiac

    QuadManiac Member

    I like your mirror placement. How'd u mount it? Less vibration than at the handlebar end?
  8. djase10

    djase10 Guest

    Rear vision mirror from KMART

    Hi QuadManiac
    The mirror is a clamp "around" type, ,
    i have it clamped on the top of the forks using a cable tie.

    Pretty much stays where it is,
    & just have to move my leg out a bit to have GOOD REAR VISION.

  9. djase10

    djase10 Guest

    Latest expansion chamber build.

    Hi All

    Here is how my latest pipe went together..

    Used part of original exhaust manifold.

    Pic 13 & 14 are the final result.

    Looks & Sounds GREAT,

    I cant tell any Power gains as yet due to heavy weather,

    THIS PIPE ==To be continued.


    Attached Files:

  10. I have been playing with the length of the stinger and found that the size and length can make major differences as well as the header length. I have a pipe like you are using, and I added a smaller/ longer stinger to the end, and it made a major difference. I believe the design of these pipes is VERY mild, looking at the long thin cones and the lack of any kind of belly.

    Attached Files:

  11. djase10

    djase10 Guest

    Cheers misteright1_99.

    Only slight belly-
    Yeah that's next on the agenda , to extend the belly,
    (I'll probably use a fly spray can or similar for the extension).

  12. beachcruiserD

    beachcruiserD New Member

    SO HAVE YOU NOTICED ANY CHANGE IN PERFORMANCE? SORRY FOR SHOUTING......im curious about expansion chambers and the peformance related with one, and how much total $ and effort you put into a well performing one too, thanks,beachcruiserD
  13. djase10

    djase10 Guest

    $20AU -1/4 roll mig wire & About 6hrs

    Hi beachcruiser.

    $20AU -1/4 roll mig wire & About 6hrs of work / r&d.

    Definite bottom end improvement all round with all the pipes i've done..

    BUT i cant be 100% decisive on top end ====
    DUE TO A FUEL STARVATION PROBLEM I"M HAVING at a certain rev range.

    It is definitely worth the effort , thats for sure,

    & extending the belly of the expansion chamber ,
    ( as picture suggests ),
    is next on the cards,

    I think thats where the top end is ,
    ( but space is also an issue), it's all R&D..

    I'll update as i progress..

    Attached Files:

  14. xPosTech

    xPosTech Member

    Wow what a neat pic edit. I think you photoshopped (or printed and snip snipped?) it rather than chop up your garage floor and pipe with a guillotine. But man, did it do a number on your finger!
    I saw a container for spare coal oil or Coleman® fuel at the local G.I. Surplus that might be ideal for matching boost bottle and resonator. Guess I'll have to pick up one or two, try them out and post pics. It comes in a beautiful metallic magenta anodized finish, teardrop on one end and squared off on the other.

    Taking my memory into consideration it was 750 ml and about 8 bucks (and purty). About the size and shape of those tall R-134A refills (Super Chill?) with the gauge on top.

    Shame it's aluminum. I'll try not to wreck the finish.

    Last edited by a moderator: Dec 18, 2015
  15. jlebh1

    jlebh1 Member

    how good do those gassles mig welders weld? i was thinking of getting one also do you think that the expansion chamber would work with the 66cc HT engines?
  16. djase10

    djase10 Guest

    gassless mig welds great

    Hi jlebh1.

    Yeah i'm very happy with the welder and recommend one,
    BUT make sure it can also take 5KG spools as well as the LITTLE 900gram spools.

    AND can use gas also.

    as for the expansion chamber thees pipes are a little small for a 70 ,
    and as mentioned B4, the belly needs extending.
  17. djase10

    djase10 Guest

    Latest expansion chamber V3 FOR 34RED

    Yep latest Version 3 expansion chamber,

    specifically designed for 34RED.

    Exhaust port to chamber u bend to muffler.



    34T sprocket
    only good for hill climbs & major head winds.

    abso usless top end, THE WORST of all iv'e made.

    Looks excellent ,

    way to loud (even louder than my stingray) without the power.

    I need the correct figures for these motors to continue this properly??.

    Attached Files:

  18. jlebh1

    jlebh1 Member

    is that the one on youtube?
  19. djase10

    djase10 Guest

    yeah the one on youtube.

    Yeah thats the one.
    Enjoy your arc welder jlebh1.
  20. djase10

    djase10 Guest

    does anyone have the correct info to fill in these boxes??

    Hi'yas all.
    Yeah, does anyone have the correct info to fill in these boxes??

    any info would be good
    as i dont have the tools to measure them.

    Attached Files: