I chose pictures carefully, I could show some where you'd see the paint imperfections in grand detail!!!
I wanted a high flow muffler, but also wanted something quiet. I'm not sure how quiet it is as I've only ran it in the shop, and everything is noisy in there.
This pretty well explains the muffler. I drilled enough 1/4" in both the incoming pipe and out going pipe to exceed the area of the 1 1/2" ID of the pipes. Then just welded the incoming to the opposite side of a 4" exhaust pipe, and one end to a piece of 16 gauge sheet. Welded the sheet to the back so the pipe exited the front.
Drilled a hole in another piece of sheet, set it over the exit pipe and welded everything. Since I'm a crappy welder, it took several beads to get things half way air tight.
The exhaust gas comes in close to the front, divides through the 1/4" holes, travels to the back, divides though the 1/4" holes, and shoots straight out the front.
My original plan involved adding packing along the interior of the muffler, but kind of ran out of room. If I do another, I might try 5" pipe for the muffler body.