Re: java pipe examples
it seems like java pipe is way out of its element with pipes the size for mopeds. It uses 'fudge factors' to calculate the pipe rather than actual thermodynamic modeling, so i dont think its worth much.
i've made 3 hydroformed expansion exhausts and after going through the work to make the first one, decided that skimping on the math is a waste of time. you're better off reading to get an understanding of what each change does, then modifying or reproducing an off-the-shelf pipe to make the changes you want to see.