Exhaust

[flyguy91318]

Hey guys I posted this a while ago on another Bimmer forum but didn't do me alot of good due to the fact not very many people have the M42 or realy weren't that enthused on it so let me get to my question!
Has anyone cut there cat and resonator off and just ran straight pipe from the motor to a muffler?? Other than emissions laws wich here in wisconsin they realy don't care much I would like to know what the pros ans cons are, if any such as will this thing not have enough back pressure is that realy a factor with this motor loss of power what?

[GrippyDrifty]

I see that you are still taken by the "back pressure" myth. What exhausts need is maximum velocity of exhaust gasses with the least amount of restriction. BUT,  when you begin to put out exhaust gasses faster than they come in (intake), you lose power. <--This is a VERY dumbed down version. I can write 3 pages on the subject. PM me if you have further questions or type in exhaust, pulses, restriction, back pressure etc in google.
That being said, I can't see an issue with removing the the cat and resonator. The m42 exhaust system is designed very well and I believe it's 2 1/4 ," but like in any exhaust system cats and resonators are fairly restrictive and I imagine one could gain a few ponies. I have not done this since I live in CA, which is self explanatory.

For refference, I found this on several sites:

 "The 2.3l e30 m3, developed 195 PS (143 kW/192 hp), or 200 PS (147 kW/197 hp) without a catalytic converter."

Before anyone reprimands me though, I must say that the e30 m3's exhaust system is pretty different from ours.

Hope this helps.