Not at all, but good research means investigation...It is possible that there may have been a typo. So I did the math and compared to a known and they don't jive. I think that would be a good reason to question the math. I understand that the manufacture may have derived their dimension from exhaustive (no pun intended) testing that may not follow a rule of thumb equation. Consequently I need more information. I do not plan to build the muffler, but am working with a custom muffler builder. His size for the chamber was 3" x 1" alum pipe being fed by a 1/2 " x 1"header and 2 3/8" exhaust pipes. The formula agrees with the header and the pipes but again the chamber is much smaller and this concerns me. This seems to be true for every one of the 13 planes I have flying, maybe the formula I used is not the correct one for volume of a cylinder?

Regards,
Randy