I have a gasoline engine, model 168 (6,5hp). I need to modify exhaust system. Current one is to loud. I am looking for option to be as silent as possible. Muffler size can be max round tube, 77mm in diameter, max 20cm long, tube from engine to muffler is 1 inch in diameter. No need for power,... just not to be this loud. See picture:
What to use in a muffler to lower the sound? Tubes, walls wit holes, foam,...?
I am looking in something like this:
or how to design?
How it's done in motorcycles? If they lower the sound...
Designing and building a muffler seems like a lot effort. I suggest that you look around for a similar engine and determine if an existing muffler can be procured and installed.
Check out those recreational run silent generators, like the Honda EU's or yamaha's.