Back when I was young and knew everything, I found some formulas for designing a 4 stroke exhaust system. Now I'm old and can't remember where I put them. It was fairly simple using displacement and cam timing you could calculate diameter and length of the primary tubes. Can anyone point me to some links or post the formulas so I can do this again?
The next challenge would be to find info on designing a megaphone system. All but obsolete now, I think these were just used to return a stronger reverse pulse and even spread it out over a wider rpm band? There's a lot of megaphoney looking mufflers but I'm sure they need to be free of baffles to work. I'm also pretty sure you need one per pipe and can't have a 4 into 1 megaphone.
Any old megaphone knowledge out there... it sure would be cool to build a Hailwood replica cb500 with 4 open megaphones.
The reason for this post is an old Yosh cb500 racing header I have that worked way better than all the others for roadracing, and had fairly small primaries that were much shorter than all the headers being sold at the time.
I could actually post the dimensions for the yosh and a Hooker header if others will contribute numbers from other known designs. It would be nice to have a database of known header dimensions and calculated ideal dimensions for various bore/cam combinations. I think most so called "racing" headers had tubes too large and too long for racing use. They were tuned more for midrange stock motors if they were tuned at all.
