The best all around muffler is kinda like picking the best car to buy-
But my own qualifications are
1 It does not have to fit in the cowling -
2 it should muffle quite well
3 it should enhance power IF possible.
4 For aerobatics - peakiness is not acceptable nor is a flat spot in midrange.
So - here is my take on it.
A header and a can or tube is just about a forgone conclusion.
The best setup for simply ease of doing the job, is a very large , low backpressure , NONTUNED device.
The Europeans have developed a few of these and basically they are like the RCS can called the JMB and the German can called the PIFA.
These quiet the exhaust note but simply do not enhance thru a tuned backpressure (wave) .
If someone has found otherwise - please correct me!
Some engines are not fussy and actually like and need some backpressure to really run correctly.
The easiest exhaust setup to obtain for these is simply the K&S and do it by the book - basically a header abut 12" long seems good for the setups I have tried.
There are more- the Chapman Vtech setup is a real booster but you better have an engine which likes it - It really can build backpressure.
Mac's has some full length pipes large enough for 40cc and I think has an even larger one .
The forty one I tried - was no better than the K&S -but I am going to re- vist the whole tuning program -now that I found out that the durn carburetor can be switched to give better midrange--this discovery was simply from cut and try - but it really worked .
It will probably work on other engines too -but WHICH carb will improve the midrange -on WHICH engine -is a mystery to me.