New Expansion Chamber Theory

Discussion in 'Performance Mods' started by jaguar, Aug 19, 2011.

  1. jaguar

    jaguar Well-Known Member

    They've been around for at least half a century but no one has ever offered an explanation of exactly how they work. All explanations have countered laws of physics concerning the action of sound (pressure) waves. I have an explanation that may interest you, not just to tickle your intelligence center but because once you understand how they work then you can figure out a way to solve the long standing problem that pipe builders have always been faced with: build a pipe with a strong hit but a narrow powerband, OR build a pipe with a weak hit and a wider powerband. (Or settle for something in between which has no strong points at all)
    Now that I've caught your attention you might as well follow through and read it all at
    Last edited: Aug 20, 2011

  2. If you post measurements in inches. Ill make you one!
  3. jaguar

    jaguar Well-Known Member

    Already have one and it works great! Now I climb hills like they're nothing. And I've not lost any top speed. A two-in-one pipe!
  4. The truth is...tuned pipes are "tuned" to the engine...the specific engine that they will be attached too. Naturally, anything is better than what is provided in the Chinese kit.

    Last edited: Aug 20, 2011
  5. Divide millimeters by 25.4 and you will get the inch equivalent.

  6. jaguar

    jaguar Well-Known Member

    thanks for the correction Jim. I changed "decade" to "century" in my fist message.
    Concerning tuning, a pipes top rpm should match the top rpm of the engine. But this two-in-one pipe has a lower "low rpm", thus a wider powerband and a good hit although hard hitting pipes always have a narrow powerband. It has broken the "powerband" barrier so to speak. Email me if you want specific info on this magic pipe.
  7. Hi Jag,

    You're right...hard hitting pipes do have a fairly narrow powerband. A pipe that offers good all-around performance is best for motorized bikes.

    I built the pipe for the morini spoiler, shown on my website, based on the specs that Morini provided with the engine. The dimensions that they provide are for a good general purpose pipe for the Morini engine. The performance was excellent for this application!

  8. BoltsMissing

    BoltsMissing Active Member

    While on the subject of Expansion Chambers.

    The subject of "variable expansion pipes" has been noted before and trashed, .... use Google,variable expansion chamber lots of "debates" out there.

    I think Lotus is still working on something.

    Conclusion so far seems to show; cost, materials, engineering and heat issues in regards to, "Variable Expansion Chambers for 2-Stroke Engines"

    the standard BS*** exhaust on a HT kit by now needs a major overhaul. Seriously, enough is enough of this carpe.
    At least, at the very least, where the pipe fits to the engine, hope they make it all matched some day soon, like yesterday, 18 months ago!

    As for the maths behind the pipe in a kit in regards to expansion etc, that can be sorted by each to their own to purchase or make their own after-market parts.

    HOW it works, the theory I think has to be understood, WHY the expansion chambers do what they do etc.
    Here's more graphical stuff, while we are waiting for jaguars theory and conclusionz.
  9. jaguar

    jaguar Well-Known Member

    Who said anything about variable pipes? My pipe has set dimensions.
    My new pipe breaks the return wave up into 2 parts, one for high rpms and one for low rpms. So it works good both at high and low (relatively speaking) rpms which has been impossible to do until now because no one knew exactly how the return wave was formed. (hint: it's not bouncing off the baffle cone because even at a 10 degree angle the wave reflects off the wall and goes out the stinger.)
  10. BoltsMissing

    BoltsMissing Active Member

    No one said anything about variables, just something I thought I throw in the ring while we waiting in anticipation.

    But you have a interesting concept,<<breaks the return wave up into 2 parts,>>
    anything that will supersede what we get in these kits will do.
  11. jaguar

    jaguar Well-Known Member

    The wait is over. The next generation pipe is here now.
    What are you waiting for?
  12. 2strokepoke

    2strokepoke Member

    neato, what thickness/material is best for makin homemade pipes?
  13. jaguar

    jaguar Well-Known Member

    I just measured the sheet metal I used to make mine and it is .023" which is fairly thick and even though I have strong hands I'm just able to bend it with my hands. I'd like to hear what thickness others have used.
  14. BoltsMissing

    BoltsMissing Active Member

    On the link I posted, they suggest the following for thickness:

  15. Can I take a sneak peak?
  16. jaguar

    jaguar Well-Known Member

    As an update I would like to add that my page on expansion chamber theory has the latest insights as to how a chamber works and why my design of extended baffle works well to broaden the powerband. Please look for that page after clicking on my signature link to go to my web site.
  17. mikejeffries

    mikejeffries New Member

    I bought 18 gauge. But haven't made it yet. And Jag keeps coming up with new cool ideas. Jaguar, I like ur thinking. I don't quite enjoy how much people try and shut down new stuff because it's new and they don't 'understand' the concepts (or memorized the phrases from their reference books). I will have to check out ur new model for pipe design -- sounds intriguing, as I often come up with stuff I wish I could try. Keep it up.
  18. jaguar

    jaguar Well-Known Member

    The latest design that I posted is very good. I will be testing another design that minimizes the return baffle wave as much as possible for the maximum torque increase. I don't know if I will post the design though because I may have found someone to make the pipes so I can sell them. Send me a message with your email if interested in buying one.
  19. BigBlue

    BigBlue Active Member

    I was wondering if a pressure transducer with a voltmeter would be beneficial when tuning a torque pipe to measure the baffle waves. An oscilloscope would be better, but who's got that kind of cash.

    I am sure it would be easy just to test the bike with the pipe on and make your adjustments.

    Found a couple YouTube videos on how to make a low cost pressure transducer that could be connected to a voltmeter or oscilloscope:
    *Click on the Show more and a detailed list of parts is listed, so you don't have to stop the video or buy any book or CD*

    Would be a cool accessory for the tool box for automotive and motorcycle projects.

    Thought I'd get throw a post out there to see if anybody had any input.

    AKA: BigBlue
  20. jaguar

    jaguar Well-Known Member

    That is the ultimate weapon for making sure a pipe is in tune with the porting. What is hard is after taking a photo of the waveform you need to put the graph lines on it that matches crank rotation, but how to know where exactly on the graph is Exhaust Opening? Obviously it is somewhere near the beginning rise of the exhaust pulse, but the "3rd wave" interferes with its shape with some port timings. (read my writeup on my site to know about that wave).
    The first video lists gas tank low pressure transducers that can be used but then vaguely says something about how PVC pipe and a hose is needed. It is unknown whether it can withstand the high exhaust temperatures. I doubt it.
    The second video says the transducers are for a max of 250psi and 500psi, both being very much higher than what is needed in this case. But if they maintain good sensitivity from 0-10psi then they'd still be useful.
    Last edited: Dec 30, 2012