Mufflers...

Can someone summarize the different types of mufflers for me please? Tongue vs dustbin, conventional etc. What does each do? What are the advantages/diadvantages of each?

thanks,

The conventional "tube" muffler (such as supplied by most engine manufacturers) has a sorta large expansion chamber and the exhaust "stinger" coming out the back, usually at an angle to deflect the exhaust away. These work by allowing the sound pulses to diffuse together in the chamber and for the exhaust to exit at a more constant pressure, thus reducing the noise. They give a deeper tone to the engine and are heavy. they also provide a certain amount of back pressure (some a lot of back pressure) which will reduce the power available from the engine. This may or may not be a factor. They are the heaviest. That is.

There are after market tube mufflers made by Art Adamisin and others that are lighter, nearly equally effective in quieting the engine, and allow more power to be produced. They cost more than the original manufacturer's muffler, however.

And then there are the variants such as the Mac's Muffler which are sort of a poor man's tuned pipe. These, again, allow a bit more power out of the engine, but only at certain (usually higher) rpms. They do not work well at the slower 4-2 break speeds.

A "Dustbin" muffler is sort of a variant on the tube muffler, except the "tube" or "bin" attaches directly to the engine exhaust. (There is no extension leading into the muffler. It just direct mounts.) The "stinger" outlet on these comes out the other side (not the back) and has a deflector inside so that the exhaust can not go simply straight through. It is almost like a two-chamber muffler, with the second chamber being quite small. These are extremely effective mufflers and light for a tube type muffler, but are not suitable for engines with a cowl because of the type of mounting used.

A tongue muffler is like an exhaust extension with the end plugged and, usually, with a number of holes drilled in the flat side so you can aim the exhaust up or down, your choice. These do not use the expansion chamber principle for muffling, but rather "muffle" the sound by muddling the frequency of the exhaust. Instead of allowing the exhaust to come out in one pulse and one loud pitch, each hole, like a piccolo, carries its own pitch. They do a decent job of muffling. We had one on Matt's plane at the FAI trials a couple of years ago, and it was (in my opinion) the second quietest engine there. Quieter than nearly all of the pipes. the noise is "shriller" however, and, in some people's opinion, not as pleasant as the deeper roar given off by other systems. These have the double advantage of being cheaper and lighter (about half an ounce or even less) and will provide less back pressure (hence, more power) than the stock (heavy) tube muffler that comes with the engine. On these you can tap some of the holes and insert short 40-40 screws to vary the number of outlet holes, which then varies the amount of back pressure and, also, to a degree, the volume of the sound emitted.

Leonard Neumann