Have always heard that the open end cap from ST was equal to 4 discs...


Jim

 

i also run 15 disc and closed cap. it was waaayy quieter than my vance and hines comp pipe and it should be cuz it was only 20'' long with a 2-1/2'' port. annoying loud on a long ride.
i ran the supertrapp for the season last year and it is by far the best pipe i've owned yet. my dyna ran better, faster and no decell pop with the ST. closed cap. (not stock engine)

 

Nope, it's equal to 10-12 discs.

I personally found open cap + 8 discs to be the best combo.