In about a week or so, I am having a custom 2 1/4" exhaust built for my 02 MC. My question for you all is this:

The guy is gonna do a header back for me, but he said if I want him to he will cut off the cat and build it from there because it won't be any harder for him to do. I wanna know what the bennefits aside from loudness will be to remove it as opposed to leaving it on there. As far as i'm concerned, the louder the better, but the last thing I want is for my car to sound like a honda civic that has a fart can on it.

So, anybody with info, experience, or suggestions...I'm open.

 

no cat = higher emissions and usually not street legal

Might hurt resale value if you can't sell it to someone in CA or any other state where they have emissions tests.

Patrick

 

Not really concerned about emissions, last car i had, definately not legal, all though with denatured alchohol in the gas tank, it would still pass. And with any aftermarket parts like this, you always hurt resale potential, which i am also not concerned about.

My sole question, is what would be best for performance.

 

If I'm not mistaken I think the exhausts that are performing well are 2 1/2" and not 2 1/4".

The header will flow better without a cat. You'll gain on the top end but I don't know if you could say conclusively what will happen with midrange.

Jeff

 

First of all you have an MC. Best cat-back exhaust for power is the Helix13 for the MC. Other good choices are Rspeed.net exhaust and the Rogue. Rough cost $450 to $550 and you can do the install yourself.

I think you might benefit from talking to Randy webb at webbmotorsports.com since he sells many of the cat-back exhausts and can tell you about expected power gains and best diameter size. And also talk to Caddman at Cat and Dog racing who has been working for a year on a racing custom exhaust design for the MCS.

Here are some concerns-
Loudness does not equal power- it's easy to make an exhaust loud but not easy to gain more than a few HP (0-3) from a header and a few more HP (3-4) from a cat-back exhaust.
Loosing the cat is risky thing to do- since the second O2 sensor lies behind the cat when you cut off the cat you remove the O2 sensor and even if you put on the O2 sensor on a race pipe it may trip the check engine light and send fault codes to your OBD II. Outmotoring sells a part to connect to the O2 sensor to allow for the check engine light not to go on.
If you want power then don't fuss with the header, just work on the exhaust.

The MC isn't really going to have enough power to make a header mod worth the effort. Racing headers with no cat aren't always the best match for the MC. It depends on which Cat-back you use- a little backpressure is a good thing for the MC. Talk to Randy Webb about the choices.

If I had an MC and I was looking at header and exhaust I'd choose the Helix13 or the others mentioned above. Good luck with your project. Have your MINI dynoed before and after and don't expect the results to be too high realistically.