Does a cat affect performance?
Im thinking about ordering the OBX headers, but I do want to run a cat with it.
Helix sells them with the original cat welded to it, but others use a magnaflow cat instead. I like the helix setup more but will it affect performance?

 

Just as with mufflers, cats can be more or less restrictive. The Magnaflow is probably less restrictive than the OEM, thus not as much power loss.
Cat-free is the least restrictive, but you risk a wedgie from Mother Nature.

 

Also it will effect back pressure, if you lose to much pressure and arent flowing enough gas out the pipe then it will overall hurt your performance yes. If you have a very high HP machine or TC setup that flows a lot more gas out of the engine than stock you will probably get more power out of the less restrictive system.

BEATNUT

 

First, running catless, not only will you fail emissions testing, but its like a $25K federal offense. Besides that.

You can try a 100 cell cat or 200 cell cat (not sure but I'm guessing OEM is 400 cell)

You also run the risk of losing low end torque as all systems require some kind of backpressure

 

From the title of this thread Im thinking that a cat got stuck between the belt and the pulley and yeah...that would affect performance. I just have to focus more.

 

Well, I just had to check in case this was posted in OT!!!

 

Im sorry if my original thread and titel may have caused some missunderstandings. Im not a native english speaker

Im planning on running a cat, only the question is whats better. The oem cat or a magnaflow (read: aftermarket) cat?
I will be running it on a tuned cooper, so no tc or sc here.

 

No, you're fine, Sidney....it's OT that can get "interesting."

 

I put a cat in the bass-o-matic once and made a little feline octane booster. Definitely felt it in the butt dyno. And seemed to clean the injectors, too. Just make sure you strain it before putting it in the tank.

 

wow...
great help

 

You'll probably get a little bit more horsepower from an aftermarket cat, but to me I don't think it's worth it considering that many aftermarket cats don't hold up.

Remember that the MINI has two cats - a small one in front of the flex joint and then a second one. The OBX (or any other header) is going to eliminate the first one - that plus the improved size / shape of an aftermarket header is going to provide the vast majority of improvement that a header /cat will provide (at least in my experience). Of course, if you're going to do really extensive mods to your MINI such as a ported / polished head and a cam then a free flow cat might be worth it.

 

thanks!