I have researched extensively, including online, in service manuals and interviewing mechanics and I cannot seem to get a straight answer.
I have a 2012 MCS stock exhaust all the way, and was wondering who could tell me if there is more than one cat in the system?
I understand that there is one in the downpipe but I have also read about another down the line. And this was on several occasions.
Any and all information is helpful!

 

The primary cat is in the downpipe and there is a second cat under the car. There is also likely a resonator under the car. If you kneel near the door and look under the car, you will see the exhaust and two larger diameter round pieces. These two larger pieces are the 2nd cat and the resonator.


Have fun,
Mike

 

That's so interesting, I had talked to the mechanic earlier today and he said that the only cat is in the down pipe, and that the other components were resonators. Mind you, this was a mechanic who works for the dealership.
The reason I ask is because I was looking to get a catback, and read in several places that certain ones get rid of this so called second cat. I don' want to void any warranty and throw any CEL's.

 

The second cat is not monitored, so you won't get a CEL. The downpipe has a O2 sensor ahead and downstream the cat, so it measures effectiveness of the dp cat.


Mike

 

I believe the R56 has 2 cats. Please check out this OEM diagram for reference. Hope this helps.

-Luccia

 

I managed to find the diagrams before but I didn't have my car to compare it to.
I think we had a breakthrough people!
I believe everyone is right and I just didn't connect the dots. (Including the mechanic who might have misinterpreted my vague question)
According to the diagram (attached below) it seems that there are two versions of the stock exhaust, both of which have a cat shown on the left (the one downstream from the DP) and either 1 or 2 silencer/resonators (I happen to have the one with 2). LAME.
Any suggestions on full exhausts/catbacks/DPs?

 

Check out our performance exhausts here.

 

the only warranty you void removing the 2nd cat is the warranty for the 2nd cat LOL

 

I was looking at the AFE catback, sounds good for a decent price. Also ran across a CNT catback as well but this one frightens me because I can't find much info on the product.
Been researching up and down trying to get the best bang for my buck.