Drone free exhaust system-solved!!!!!!

[ainarssems]

I guess with a J pipe you have 2 benefits, it's easier to find a space for another pipe running parallel to main pipe and because of the bend it does not have to be very precise as effectively you have several different length pipes. If you follow inner radius of the bend the distance to the end of pipe is shorter than on the outer part of bend. So 90 degree pipe or sphere will be more effective at 1 particular frequency say 100Hz but will not do much if it frequency is a bit out, J pipe made for the same frequency will be a bit less effective at 100HZ but will have wider range say 98-102Hz because of different lengths on inner and outer radius of bend.

[Borys]

In the end of the day it works. I've done it with one attempt. Its not that complicated.
Basing on my experiance 30" will cover rpm range from 1100-2000.