Originally posted by AirKnight:
What if the ball don't come out? What you gonna do then? 
Originally posted by Bruce Herring:
[b]he said if you can drop a matching diameter ball in one end of the pipe and it rolls out the other the exhaust gas wont care how many bends it passes.
Then you borrow your wifes favorite toy and poke that damn ball out of the pipe!
But seriously, the point was that gas flowing through a CONSTANT diameter pipe flows better than a changing diameter pipe.
Though i don't fully agree with the statement based on my fluid dynamics classes (yes i do have an engineering degree even though i'm not a practicing engineer). Every bend in the pipe will slow the gas down to some extent because gas is made up of particles and those particles will tend to want to go straight and hence "coagulate" at the bends. Now the amount that the gas slows down may not even be measureable with a single bend but it does slow down.
As a good example, take a dirty or painted 90 deg bend and stick a bead blaster nozzle in one end, pull the trigger for a second, and then look at the inside of the pipe (after letting go of the trigger :p ). The majority of the material will be removed from the outside radius of the bend.
But there are so many variables in exhaust design that i just decided to leave it to the guys that do it for a living and have the advantage of real world experience.
In short a properly designed single outlet should be able to net the same or more power increase as a good quasi dual. And no, the guy at the local muffler shop (in most cases) is not qualified to "design" an exhaust system.
