I had 20 disks and a closed end cap in my SuperTrapp SuperMegs. I switched to an open end cap and lost some low- and mid-range power. Dropped down to 9 disks and damn, the difference is amazing! There's a very noticable improvement in throttle response and power in the low- mid-range, and even top end "seems" to have a little more umph. I really love this tunable exhaust approach, and with the open end cap these pipes sounds just the way I like. And to thin that not long ago I was going to dump them because they were too quiet. They just needed to be... personalized a little.

 

do you have to retune the fuel mixture with every change?

 

Keith,

The SuperTrapp Website provides good referrence "starting points" for the number of disks for some applications. If I understand correctly, the idea of a tunable exhaust is to give you the ability to make minor corrections without having to resort to rejetting. If you're running just a bit too rich you can probably compensate by adding a few disks. Vice versa if you're running too lean. Also, if you want to run a high-revving race motor you'd want to add a boat-load of disks to allow the engine to operate optimally at the RPM range you will run at. That sort of thing. So one exhaust system can be tuned to several applications.

But the short answer is, if you make a big enough change at the exhaust, yes you'll have to rejet.

 

That is handy. I have always liked the idea of a exhaust you can change the sound of.

Guess you would have to keep a eye on the plugs.