Exhaust Physics Questions!

ROM:you mean the lennox sledge hammer furnace?when theyre not running right you can usually here them pounding from about twenty feet away! haha

Exactly. Without it's mufflers or pulses not timed right it sounds like a farm tractor in your basement. They timed negative pressure waves precisely to draw fuel into combustion chamber. A marvelous idea actually and an excellent example of basic pressure wave use to draw fuel and scavenge exhaust.

A really good book if you can get it is A. Graham Bell's performance tuning theory and practice. Its got a section on different header designs and explains all the theory.

Basically, the correct name for an exhaust pipe is an attenuator - because thats what the primary pipe does. There is a whole bunch of math that dictates what length, diameter and shape these need to be.

In basic terms you have an exhaust gas charge which you want to remove and a power wave which you need to tune (attenuate). Also, you want to use the reflection wave to either scavange the cylinder, or back pressure it to get better combustion depending on how you are tuning the bike.

After that you have a thing called a collector which is where the primaries usually join, a tail pipe, then a megaphone then a baffle. All these have a bucket of math dictating how they all work together.