Exhaust How to make a muffler that is super quiet / max stealth - pics

Discussion in '2-Stroke Engines' started by professor, Sep 29, 2009.

  1. professor

    professor Active Member

    The first pic is to show this particular muffler that is in 2 sections. it is made out of a small electric motor weather enclosure. It does not have to be in two sections. This is what I had on hand. A used fire extingisher or any cylinderical light steel tube would be fine. In my case I had to fill a couple of small holes and adapt a tube to one end:


    The white you see is what makes this a lot quieter than a normal muff. It is fiberglas wrapped around a heavy wire screen. Any kind of fiberglas will do, even old window curtains made of the stuff.
    Here is a pic of the insert:

    Each end tube has holes drilled around the part of the tube that goes in the muffler housing and the end capped:

    The drilled pipe could be one straight piece with a divider in the middle(maybe 2 dividers to separate the noise a bit rather than my offset style with 2 pipes.

    This one is going on my 24 inch FS 6hp mountain bike. Just playing around and yelling into it- this thing is great.
    Maybe I'll do a sound meter check at the rear of the bike later on.

  2. Fabian

    Fabian Well-Known Member

    I would be very interested in the db meter check - for me, the quieter, the better.
  3. professor

    professor Active Member

    Hi Fabian, the muff is mounted on my 6 horse (a work in process shown in the "Wild in the streets" section) and I gave it a shot of ether and some oil-pulled the rope and it sounds like a mellow, stock old 350 honda. Only gave a couple of power pulses. Not as quiet as I had hoped for (dead silence?), Waaay quiter than the goofy system toro had on the snowblower it came off of.
    As soon as I get it done I will bring the sound meter home and check it.
  4. 210061741

    210061741 Guest


    Good work.
    Wonder if i could take my SBP expansion chamber and modify the muff.
  5. professor

    professor Active Member

    As long as you place the muff on the end of the ex. chamber, you will be fine. This way it doesn't interfere with the reflected waves in the chamber.

    An xtra note on exhaust in general-the longer the system - the quieter it becomes. More than one muffler= quieter yet.
    I once ran a v-8 Ford with one glasspac in the middle and one on the end in the tailpipe. Though the whole system was straight thru, it was very quiet.
  6. 210061741

    210061741 Guest

    I really mean it would be nice to modify the existing muff.
    Is it too small or is it possable.
  7. Foximus

    Foximus Member

    Just remember to replace the fiberglass every 3 months or so, otherwise it will not muffle.

    You would also drop a large amount of decibels, (and i mean a large amount) by modifying your exhaust to have an interior stinger, instead of an exterior stinger. just make sure you countersink it in past the beginning of the baffle cone, or youll lose power.
  8. professor

    professor Active Member

    Maybe it's the material I use, but I have never needed to replace the fiberglas in the inserts I have made which I use in my dunebuggy. They get a good coating of black from the exhaust,but the material stays fine.
    Good tip on the interior stinger.
  9. Foximus

    Foximus Member

    the glass will never actually burn. Put real nice quality glass (even the cheap homedepot stuff is relatively burn proof) in a fire, the next day it will still be intact. The problem is that it gets clogged with 2 stroke soot and gunk. Once the cloth clogs up it no longer absorbs much sound.
    richard jewett likes this.
  10. bAllah

    bAllah New Member

    pix r dead reup pls
  11. ZipSnipe

    ZipSnipe Member

  12. CroMagnum

    CroMagnum Member

    One resource that most people overlook is the free web space that comes with just about every ISP account. Post your pics there and you have complete control over them.
  13. loquin

    loquin Active Member

    Well... if you upload the pictures HERE, they'll be stored here, along with the post, and as long as the post is here, the pics will be here too.

    There could be all kinds of reasons that pics stored on another site might not be available when you are looking at the post here.
  14. Lucknuts

    Lucknuts Member

  15. PooPooPeeDoo

    PooPooPeeDoo New Member

    Your kind of right.....

    HOW the fiberglass lasts, whether it burns out or remains a bit sooty or whether it oils up, depends upon a ratio of three things.

    1. The tuning and oil mix of the engine - lean / rich - oily/ lightly oiled.

    2. The distance it is from the engine - as to how much heat the pipe loses = ambient temperature, wind speed, insulation levels inside and outside the exhaust etc..

    3. How the bike is ridden - toodling along with the odd bit of high power away from the lights or up hills, OR riding it flat out everywhere... what we want is the average riding style of the rider.

    Well it's these three things that determine, whether the fiber glass will burn out, or whether is gets a little sooty and lasts almost forever, or whether it oils up and or becomes coked up - like an oily sponge / charcoal brick..

    It's not whether it's fiber glass or not, it's the circumstances it will generally be exposed too, most of the time.

    And enduring variations - such as living in the flat lands for years, the fiberglass is fine, and then going for a week through the mountains under full throttle for ages up HUGE inclines.... which burns it out.

    Or fitting the muffler to a NEW engine that has to be run in at 16:1 oil level and at low speeds like 20Kmh for he first 500Km.... which clags it up with oil and carbon etc...

    It's not an either or issue, it's purely circumstantial.

    Use the fiberglass, and if it works out fine, keep using it, or switch from roof insulation to a HEAVY fiberglass matting if it gets too hot, or wrap your pipe with a layer of the fiberglass mat, to keep the heat in, if the muffler is too cold to burn out the coke and oil....


    My 35*C here, might be your 35*C below zero there....