Quote:
Originally Posted by kitw
I think the Perf muffler sounds a lot better than the modded stock ones. It really has a nice harmonic, like the OP said. I liked the sound a lot, just not the raspiness that it got when you remove the cats.
(BTW, most exhausts will get raspy when the cats come out, some mufflers are better than others at hiding it)
If you look at the BMW perf exhaust, it's completely straight through. Pretty amazing design, I'm shocked at how quiet it is, given how open the muffler is. You could easily roll a golf ball through it with room to bounce! I suspect the cans hang down simply because they have to, since it's all helmhotz resonators and chambers around the piping.
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Yes, and here is a pic of what kitw is describing:
A look inside the inlet side of the BMW Performance exhaust. You can see the exhaust tips directly on the other side (where the "Y" split is and the perforated tips). There is an inlet upwards as soon as you enter the muffler "can", and this may be a Helmholtz chamber, which seems to be on the top side of the muffler. Very interesting design and it is very surprising how quiet the exhaust is given how straight-through it also is. Not sure how the pipe that connects the two sides come into play, but the sound from the exhaust is harmonic or almost (musical) organ-like, in a good and interesting way.