Just to show some simple and quick 2d calculations using a 0.6" inlet and a 0.75" outlet, and a very simple representation of a muffler.
the first picture is the pressure contour... someone correct me if i'm wrong, but i think i recall a lower pressure drop = more flow (ie more velocity)
there are areas of low and high pressure...most notable is the highest pressure right above the outlet (which may be drastically reduced if there was a radius on that corner)
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Next is the velocity vector profile, notice the correlation between the two images. the vectors are most helpful in showing the air's path through the can.
The calculations were done using the mass flow rate of air exiting the cylinder of an 026 operating at 10,500 rpms.. (0.0104400625 kg/s).
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Kinda fun i guess to see inside of what's going on. Im sure there are much more accurate ways to model this, i only did this very quickly.
It may be possible to "reenact" TimberWolf's experiment just to validate the computer results...
is this very useful? probably not unless you work for a chainsaw company...
I personally still like the idea of going a little at a time to notice the changes and learn that way