Originally Posted by
earlwb
One thing worth noting is that the reverse cone on the muffler/tuned pipe works best if it is a straight tapered cone. A curved cone doesn't work as well. Less of the shock wave gets reflected back towards the engine when the cone is curved. Thus the short fat muffler chamber using a curved cone is not as good as the long skinny muffler with the straight tapered cone. When you look at the tuned pipes and expansion chambers they all use a straight tapered cone shape.
But anytime a muffler lets the engine develop more power than just using a open exhaust makes that design successful. So both of your designs are good.
Thanks for the suggestion. I was trying to duplicate the jett mufflers or ultrathrust mufflers but the metal was just too thin to get a deep enough bell.
I am going to try to make a tuned muffler taking the measurements off of the 90 size ultra thrust muffler. I figure I will make it just a little long to begin and just keep cutting it shorter and shorter until I get it right. Then I will weld everything in place. Do you think that instead of the curved cone on those mufflers, I would do just as good with a straight taper cone?