Im running a set of Leo Vince / SITO 4 into 2 exhaust. I like the look plenty but I want to get more rumble out of the bike like my last aftermarket set had. There is a part that is riveted on the end of the pipe that looks like it contains a baffle system. Anyone ever have any experience with uncorking a set of mufflers like these? Im hesitating drilling out the rivets and exploring the innards as the mufflers were hard to find and not cheap either..... Thoughts?
What is the Leo Vince model of muffler? They look terrific, can't find them on line tonight.
Some theory for your thoughts:
Most quiet mufflers are a reverse-flow type, which means the chambers inside have a pipe of some sort that extends through a baffle wall, then deep into the 'back' of a chamber, and the exit from that chamber is also very long and usually at the 'front' end of that chamber. This prevents the sound shock wave from finding its way directly from one chamber to the next. It also evens out the exhaust pulses, making for much more even backpressure, and far less tuning headaches, than when these passages are very short. Shorter pipes between the chambers increases the sound level (by letting the shock waves pass through) as it reduces back pressure in certain RPM ranges, but it also tends to make those high- and low-pressure RPM ranges uneven as the pipe lets more pressure waves pass through.
So, if you remove the baffle and find the long pipes reaching from chamber into chamber and wish for more noise with similar backpressures to remain, one method is to drill cross-holes (large ones) into these pipes to make them into diffusers. Then some of the broken-up pressure waves will migrate from hole-to-hole in the pipes, while the pressure itself remains in the chamber to a large extent - this helps improve the tuning by preserving much of the backpressure. If you just cut off these pipes, the pressures fall dramatically and erratically, and tuning problems gather quickly.
Quiet pipes also generally have strong outer walls, or even double thin walls (like old Beemer mufflers) if weight is an issue. These last MUCH longer, as they don't flex with each pressure wave, wearing themselves.
