Originally Posted by slammedm3
whats the difference between getting rid of first or second cat?
Also..how would it sound?
Don't know how the sound would differ vs. one or the other. If removing a cat, expect it to be louder.
The first set is right off the header. In my opinion, this is the greatest restriction in our exhaust system. When aftermarket headers come, you can be sure they will delete the first cat. Deleting this cat, is what I think makes the most power for the aftermarket headers for the S85. I believe this will carry over to the S65.
Turner, for example, just deletes the first set off cats off the newer M's and provides matching software that is equal to gains with aftermarket headers.
The secondary cat is easier to delete and does not give a CEL. It can be done without a complimentary tune. It is further down stream.