Soooo, as noted in another post, I'm considering replacing the exhaust in my '08 MCS. All stock currently. I'd do it mostly for sound purposes and perhaps any performance gains possible down the road after a new intercooler and tune.


I would really like to do one of the systems that eliminates the "second" catalytic converter, such as the Quicksilver. I understand that the primary one is part of the downtube and that's the one that is connected to the emissions sensors. We have biannual emissions testing here in my local county (via connection to the OBDII), so it is my understanding that removal of the second cat would not cause a test failure.


However, the local muffler shop I called told me firmly that they would not remove the secondary stock cat as they would be liable to pay a $25,000 fine. They did note that if the secondary cat does not contain a "ceramic brick," they would be able to remove it. (Please save me from "just do it yourself!" comments. I am NOT a mechanic and I do not have mechanic friends. Most times if I try to "DIY" something it ends up costing more to fix it than it would have cost to have a professional do it in the first place.)


Ultimate question - what is the nature/internals of the secondary cat? Does it or does it not contain a ceramic brick?

 

Are you talking about a Quicksilver header or a Quicksilver cat-back exhaust or both?

There is a pre-cat between the primaries and the main cat of the oem manifold (downtube),
then the bigger main cat further downstream. The intermediate pipe (part of the cat-back exhaust) has
a resonator which is not a cat and is not necessary for emissions purposes.

 

The 2nd cat does have internals like most any other cat. Just find a shop that will. I had no problems getting mine removed, just asked around and a friend knew a muffler shop that would.

It's not monitored so OBD testing won't have a clue it's gone.

 

I'm sorry, I was thinking of the Gen 1 exhaust system.
Please disregard my post above.

 

For resale purposes, I think I'll probably just leave the second cat as is and delete the resonator. Oh well, maybe I should learn that DIY thing!

 

The resonator is not restrictive, the cat is, so that's the one you want to cut out. I found a muffler shop that did it for $20 CASH. Find a shop that does not do emission testing. The shops that also test for emissions are more apt to say no. Also call it a resonator when you ask even though you know it is a cat. Don't really worry about resale. The earlier 2nd gen JCWs did not even have it from the factory.

 

Just have whatever shop you find take out the second cat and resonator and be done with it. Spend the money you were going to use on exhaust on suspension. Stock exhaust sounds good with the second cat and resonator removed.

 

I am aware of this, which is why removal of it does not result in an CEL on the MCS. However, if there was a stock catalytic converter, the shop does risk legal liability if it is removed. I suppose there are shops willing to run the risk, but the one I called was not.


As for emissions testing, that's sort of irrelevant to the issue since our testing is OBDII and not a visual inspection or tailpipe test. I have no doubt that it would pass Ada County's inspection without the second cat. Rather, the issue is simply removal of it - if it came stock and has the standard catalytic internals, removing it is a violation of federal law, regardless of whether it affects the emissions. Stupid result, yes, but nobody ever accused federal regulators of coming up with practical solutions for anything. What really annoys me is why Mini installed a second cat in the first place if it isn't needed!?!?!?


Simply misrepresenting to the shop that it is not a cat but rather just a resonator (ala Nissan's second cat) doesn't give me the warm fuzzies either. Then, should there be any liability, the shop comes after me personally for the fine due to misrepresentation. If they were willing to shoulder the potential fine and knew of their own potential liability, I'm fine with that with the caveat that the EPA's regulations also impose personal owner liability for tampering with an exhaust system, not just muffler shop liability.


I'll probably do a cat-back system and leave the second cat for now. As for saving my money for suspension mods and other mods, yes, those will be done anyway. Forge or Helix FMIC is on the list before the exhaust anyway. Sounds like a lot of people leave the stock exhaust and simply squeeze the front end for more power.

 

No shop in their right mind would tell you that they'll cut out a catalytic on the phone, they'll all say no. You just have to show up with cash in hand and ask. As far a misrepresenting by calling it a resonator the muffler shop knows exactly what it is,...wink, wink, nod, nod. If that's the worst thing you do in life you've lived pretty well.

Even though the 2nd cat is not need to pass emissions (the real sniff test) I figure that it does help the manufacturer meet ultra-low emission vehicle criteria.


Here's a picture of the internals:

 

I just went through this on my countryman. I could not find a shop willing to do the work because of the $25,000 fine AND 5 years potential prison time. I ended up going to my local parts store, bought pipe and clamps and "rented" an exhaust chain cutter. Was able to cut out cat, clamp pipe in it's place for less then $30. I immediately went to a muffler shop and told them I removed a resonator myself and didn't like the way it turned out and wanted them to fix it. They did a great job and my exhaust is 2.5" from the downpipe back and sounds great.

 

Very creative. Now, if I only had jack stands and any sort of DIY skills!


In reality, my fear is still resale. I'm not one to keep cars very long and I always sell private sale. Any smart buyer is going to have it inspected by a professional, who will likely note a missing catalytic converter. I personally wouldn't purchase a used car that has been modified illegally. I may throw on a fun exhaust for the sound, replace the intercooler and get a stage 2 tune and leave it at that. It's all fun and games anyway. (First world problems!!)

 

I bought "rhino ramps" for around $50 so I could drive my car up onto them versus findind good places for jackstands. The cutter and clamps were extrememly easyto use. Even upon inspection you shouldn't have any problems, all of the emissions hardware is still in place. Some mini's didn't even come with the second cat (jcw models). I can tell you that if you do only second cat back exhaust you might be dissapointed. I only really noticed a good sound difference after removing second cat. Now I want to remove the first cat with a catless downpipe but don't want to deal with the CEL I would get. Guess I need to save up for a tune.....again first world problems

 

+1

 

Just had the Magnaflow cat back exhaust installed. Their kit deletes the resonator. 2.5" pipe, 3.5" tips. Sound is nice and deep and not terribly loud. This is my wife's daily driver, so I didn't want it to be too obnoxious. Seat of the pants feel is slightly improved throttle response. Definitely better throttle response in Sport mode. Took me by surprise the first time I gunned it in Sport. Would it be better with the second cat delete? Of course. Am I disappointed? No.

 

Any performance difference noticed from removing the second cat only?

 

And was there any sound difference (slightly louder or deeper)?

 

A more free flowing exhaust post-turbo will always give gains on any turbo car. Are they measurable or significant? That's a whole other question. But the sum of a bunch of little gains is a big gain...so do it.

sani