Late last summer, I completed a Stage 2 upgrade on my 2009 Ultra Classic, part of which included a Dynojet PowerVision and Screamin' Eagle Street Cannon slip-ons. When I was done, I took it to a local independent shop and had them put it on their dyno and build a custom PowerVision map for me. After riding with the Street Cannons for several months, I've decided to try something different and have settled on the Kuryakyn Crusher Mellows. The Crusher Mellows have a similar type of perforated baffle as the Street Cannons, but, whereas the Street Cannon baffle is straight-through, the Crusher Mellows have a disk tack-welded in the baffle about 6 inches from the end. The disk has a small (maybe 1/4") hole drilled through the center of it. Obviously, with the disk in place, the exhaust path through the muffler will change. My question is, will it change enough (or will enough back pressure be created) that I will have to have the bike re-dyno'ed? Kuryakyn claims that their mellow and non-mellow mufflers have the same performance, so I'm hoping the answer is, "No". I'm going to call the dyno shop and ask for their opinion, but I would appreciate hearing from the experts here, too.

 

Mellows flow more air than the Street Cannons. If you experience a stutter during tip-in, there's an indication that a retune is warranted. I typically see more torque, sooner, with the mellows, and equal or better Horses than the cannons.