[normcaldwell]

Originally Posted by EricSMG

Yeah I understood you. I'm saying that if you weld in cats in addition to the resonators it will be quieter than it is now no doubt. BUT - if you weld the cats in place of the resonators it might be a wash.

No clue about the OE cats although I seem to read a lot about the Euro cats being 200 cell.

Norm, you want to confirm?

Originally Posted by mredwin25

I see, but no I'm not planning on removing the resonators, I'm just confused, I don't know if the difference in performance between the 200's and 400's is that big, I'm pretty sure that 400's will do a better job at killing rasp.

Is the Euro model as raspy as the US model? Do you know?

According to the designer of the E46 M3 exhaust, Arvin Meritor, the euro cats are 200 cell.
http://www.unofficialbmw.com/images/e46m3exhaust.pdf
This also matches with the pics from Jack at Custom Performance, where he shows 200 and 400 cell cat material.
See post #434 at http://www.m3forum.net/m3forum/showt...240056&page=11

When I looked at my OE US spec cats, inside the headers, the cat material also looked like the 200 cell pic from Jack's posts.
I don't know for sure whether the US spec cats are 200 or 400 cell, but they looked like 200 cell when I compared them to the pic.
Edit: I looked again at Jack's post. Even though I thought my US spec cats looked like the 200 cell pic, I'd want to look at them more closely.
Kind of a moot point, as I'm on the Euro cats now, and the Euro headers/cats flow way better than the US spec setup.
And, the cats should still pass the sniffer at the emissions station - I'll find out some day.

Regarding rasp: I have the Euro Headers & Cats. So, section 1 has the two 200 cell euro cats, but no additional resonators.
The rasp is present, but it sounds better (more 'exotic' so to speak) than the US spec setup where the cats are in the headers, and section 1 has the one small resonator.

If you really want zero rasp with your setup, check out the Custom Performance section 1 and 1&2 offerings.