Easy to build muffler



My Mitsubishi TLE 43,reputed to be a quiet engine has turned out to be a lot louder than I had expected.Therefore I have embarked on a project to build a muffler using readily available components, which would be easy to experiment with and would not be too hard to take apart in order to make design changes.
My design is based on a form of the "Swiss aircraft muffler approach,in which a porous center exhaust tube surrounded by loosely packed fiberglass cloth is put inside larger metal tube.The thin glass fibers are instumental in absorbing sound energy. The inner tube is usually made of some kind of metal mesh or is a solid tube with holes drilled in it.It occurred to me that a wound wire helix would work just as well,if not better,that this would be easy to do, and that you could get more exposure of the glass fibers to the exhaust gases and consequently might get better sound absorption if instead of a single one, a number of these helixes were deployed.
In my junk parts bin I found two 8 " long 1 1/2 " diam. chrome plated brass drain pipes left over from a kitchen renovation,one suitably equipped with an elbow that could be fitted together to make up the outside of an "L" shaped muffler.The engine exhaust would be fitted to the vertical leg and a bracket mounted on the engine to secure both parts of the muffler together, using clamps.
For the inside, I fashioned 5 helixes ,one 3/8 " one in the middle functioning as a "backbone",the 4 others surrounding it with about about 9/16 " diameter each,The wire size was 19 gauge, could have been smaller but I did not have any on hand,The pitch was about 1/8
Each one except for the center one was wrapped with fiberglass cloth and tied up with fiberglass strands,then the whole assemblage was arranged to surround the center helix,tied up and again wrapped with fiberglass roving,which was again tied up.The wire extensions of the helixes were all twisted together and a wire attached to this 9 " "sausage".With this wire it was easy to pull it in place inside the 1 1/2 " tube
For the horizontal section I used a simpler configuration using one 3/4 " center helix,again wrapped in fiberglass cloth,tied up and shoved in the 1 1/2" tube.
Attaching the top of the muffler to the engine presented more headaches than building the thing itself !. I did not want to braze things together,as I wanted to be able to take it apart.I had envisioned a hose clamp and some kind of end cap.I had a brass 10 mm elbow that could be made to fit the exhaust outlet ( with a suitable sleeve),and as luck would have it found an obscure chrome-plated circular pyramidal gizmo at Lowes that I could adapt to fit over the muffler tube,with a lot of snipping,to secure it with the hoseclamp.
Preliminary results are encouraging.The engine sounds much more mellow and muffled,the objectionable staccato highs are gone.I haven't noticed much effect on performance sofar,but I'm still running-in the engine.Subsequently I intend use the 5 helix setup instead of the single one in the horizontal section, to try to find out wether it makes a noticeable difference or not, which is no sweat, since whole thing can be disassembled and put together again in a jiffy.
sounds interesting, would be interested in seeing some pics of this muffler if you have them
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