Question bout mufflers...

[Half-breeder]

No... not too busy(detailed... not busy... hehe). As far as the 'amount' of packing... pack it full and tight. The looser the packing the more higher pitched frequency emitted slips by. Try to think of yelling in an empty room w/ NO carpet, and a smooth ceiling, while listening to the sound outside a window... NOW... picture the same room and same yelling, but lay carpet on everything... now picture the same room/carpet/yelling, w/ the window opened wider... see my example?

I too like the Flowmaster rumble... but yea they dont make straight flow exhausts... I 'do' know(from doing my homework) that the 'tone' that we are looking for is going to need a 'resonator' to produce(that is what is holding my fab on hold... atm). Flowmaster's mufflers have one 'built-in' w/ their designs. The basic use for a resonator is to remove sound 'impact'(the initial BANG...in gun suppressor terms, the 'blast-chamber' or primary expansion chamber)... the muffler itself is designed to 'muffle' the remaining sound/tones... and the outlet(diameter of the exit) deals w/ the volume/db's.

 

[danssoslow]

You wouldn't want the packing too tight. The pinciple on how fiberous fill works is by converting the energy of the moving air into fibers, thus dissipating that energy. Air moves through, the fibers resonate, and the energy is lost. The tighter the fill, the higher the resonant frequency (thus cancelling a higher frequency); but a point of diminishing returns will be reached, and then you are simply taking up volume.
The best cource of action would be to somehow make the muffler modular, allowing you to experiment with how much fill to use.

 

[Tig]

The best cource of action would be to somehow make the muffler modular, allowing you to experiment with how much fill to use.

Hence the reasoning for me to post pics of that muffler. You can remove or add to get the desired sound.
By going with a larger case, you will have a wider range to play with.
Another option would be to find a 50cc 4 stroke muffler and play with it.
Or, buy some oval tubing and make one at your desired length.
Is there a market for custom Kart mufflers?
I could make some to your specs if the market is high enough.

Here, this may help you guys out with the perf tubing. And, its reasonably priced
http://www.lachoppers.com/catalog/display/1134/index.html

 

[firemanjim]

Daniel, in your opinion, would the Helmholtz theory work on a straight header (ie candy cane)or do you have to have a muffler? I decided to try an adjustable. Gonna make a tube that will slide into the main tube of the resonator. After reading/searching for a couple hours, I decided that a 1/2" i.d. tube will be the main part, about 2" long @ a 90° from exhaust. Then, starting with about 6" of capped tube, I will rev engine and keep adjusting the pipes length untill I get the tone I want. Does that sound right or feasible? Tube size and lengths?

 

[danssoslow]

I'm only familiar with the theory, I'm ignorant of the practice; but here are some things to keep in mind. Tuning the resonator is no different than tuning a port in an enclosure. The fact that the entrance is the exit is what insures a 180* phase, therefore a cancellation at the port's (resonator's) frequency. So some basics of port tuning will apply here, for the mouth opening: the larger the opening, the higher the attenuation (very inportant here as its openng is in fact smaller than its physical size, since there will be air flowing in both directions through the opening); and the more volume the resonator has, the lower the tuning frequency will be. There is also a relationship between the opening and the volume of the resonator; for a given frequency, as the area of opening is enlarged, the volume of the resonator must also increase.

I've never made anything like this on such a small scale, with higher tuning; but here's a little experiment you can try before welding it in to give you an idea of the frequencies you'll affect: blow across the top of the opening, like you would a soda bottle to make it whistle a tune. This will be the same tune induced into your header.

 

[firemanjim]

Youre speaking german..... So, if I want a lower deeper tone, I want to use a bigger chamber,with a large opening at the port? Or the opposite?

 

[danssoslow]

The opposite.

Have you ever tried to listen to a subwoofer outside of an enclosure? It doesn't make much sound at all. The reason is due to phase cancellation. As the other side of the speaker is making the same sound, 180* out of phase with the front of the speaker, but sounds cancel out. This is how the resonator will work.

In the automotive industry, this method is typically used to kill the drone found in some exhasut systems. The new Camaro uses a Helmholtz Resonator muffler for this purpose. So in most practices, it is used to attenuate (lessen) lower frequencies.
This doesn't mean that the theory only works in that manner. Create a what will amount to a whistle, and that pitch will be attenuated in the end result. This can work to our advantage, beings that we are dealing with small engines and a small scale, since the frequencies we wish to attenuate demands a small volume resonator. How small? This is where you'll have to experiment to find out.

In the end, this method is basically adding a little exotica to our norm. Unless you stumble apon something we haven't considered, it will more than likely be less efficient than your typical means; but it will look cool!

If your ultimate goal is to sound deep, face the header's exit down toward the ground, and use a wide tip to end the exhaust. This will amplify the lower tones, and give you that Harley sound. Weld a 3-4" exaust tip to outside of an RLV, or even one of the bigger HP Briggs screw on mufflers (no sense in reducing flow), and you'll get that "burbble, burbble, wooomf!" I promise!

 

[firemanjim]

Pickin up what you're laying down.....back to the drawing board.....I will let y'all know what I come up with.....Also, do you have to use a muffler for this to work or can it be a header? I like my header and how it sounds, just has that high whine Id like to get rid of..... it only makes "that" noise at a certain rpm range.....

 

[Half-breeder]

Finally had a 'reason' to have to make the 'muffler' I had planned from the beginning...

Just as in the previously attached photo of the little mini tube muffler, I got one... went to the shop and found an exhaust pipe the exact ID diameter as the OD of the muffler. I cut a section off and gave one end a slanted cut(get it... 'slant'... Japanese flag/motor/owner...). I slid the pipe over the muffler n welded it together.

The header is made out of a metal swing type chair we have layin round(the section used was a support brace that kept the 2 sides of the seat from collapsing... U shaped. I cut out both 90degree curves, and welded together at the appropriate angle(was alil off... gotta bend 1 angle a bit to the left). The threaded collar I got at HDepot.

The sound, IMO(from a distance), reminds me of a Harley... to a degree. https://www.youtube.com/watch?v=WZuzF1XzYl0&feature=youtu.be

 

[Oxymoron]

Looks good Tihm, sounds good too!

 

[mckutzy]

That kinda sounds like mine.... But since we all mainly have the same motor, it shouldnt be all that a surprise.
My exhaust has a bit of lower tone due to the length, but basically the same note overer all. Kinda Harleyish with out the extra plunk note in the cycle.