headers with or without cat???

which one would be better for performance??

 

theres been very little gains to be had without a cat... search around the forum

run a cat... u wont be killing what's left of our ecosystem

 

I agree, run a cat. Otherwise you'll be getting codes (unless you trick the sensors (map, ibelieve)).

Nik

 

I recently had the Pre-cat cut out of a stock header and replace with what looks like a 3 inch piece of exh. pipe. Can't tell if it sounds different...think it does, but it def. feels better in at the top end. I'll be dynoing my car soon, just waiting for one more part before I do it. My MCS still has stock pulley btw. I'm doing the pulley last.


James

 

at the top end no cat or muffler would make the engine let air out fastest.... but in a dyno i hardly believe it will make a dramatic difference...

i heard from a friend who says in german forums people taken out the pre-cat would yield about 10 hp gains... i find it hard to believe.. so post up ur results when u do have it

i ran without one muffler (muffler joint came loose), and i can defenitely tell the top end seems faster, but suffers hugely from low end torque! hills before i can take in 5th gear i just lose speed and force me to downshift

 

I have the hp racing header that is catless and when I put it on i found that i had a significant amount of more power in the upper rpms....nothing huge....but a little more kick in the pants . It's on a cooper so i don't know about you "s" guys but i think it will do well for you as well. CES light came on though and when i switched the header back for it to go to service....they didn't say anything about the header but they did say that my "aftermarket" exhaust messed with the AFR in the engine which made the code come on. I did also run rich.... so if you do plan on doing a catless header.....make sure you know someone that can tinker with the computer and to take off the CES light. I don't know but i think that autozone can do it....i hope.

Thanks
Your friend Ben