I've also wanted to know how they worked! Thanks!
But... now I've got more questions, of course!
So... I see the inlet emptying into the first chamber. Was it meant to exit through just the one hole we see, and the rest of the tubing rusted away?
Then there's a tube connecting the first and third (end cap) chamber.
Now the question: how do the gasses pass from the third back to the second (middle) chamber?
There's a guy in the area here who used to build stainless mufflers - Tom Webb. One of his friends did some research on exhaust technology and came up with the idea that BMW built the mufflers backwards (whatever that means). So Tom built some as directed and with only a slightly throatier note, produced 7 more HP on a 90S in a dyno run. They give the feeling of being in one gear lower.
I've always wondered just what they did to achieve that result. I asked him, but didn't get much of an answer. Perhaps I'll have to have him draw me a diagram.
Wanted: Dead, smashed, crashed or trashed gauges
BMW GAUGE REPAIRS - TACH*SPEEDO*CLOCK*VOLT METER *PODs & LIGHT BOARD*