I'm planning to remove the exhaust from my lift engine as it weighs a fair amount and gets in the way if you come out of the craft. It probably isn't all that tuned either.

I'm in 2 minds whether to hydroform a properly tuned exhaust (where do I get plans for this from!?!?!) or just put a simple pipe / muffler on.

Are there any documents explaining how one determines the length / width of such a muffler / etc?

Actually for the moment I think just a simple one will do, maybe get the thing working right first

I'd assume the pipe would be the same width as the stub already supplied on the engine, then I have to extend it to a set length or does it matter too much? Then add the absorption stuffing over the last x mm of the pipe?

Sorry I am totally green when it comes to exhausts!