Unofficialbmw.com

[Invain]

Hey there folks,

I've been moding my 330 since I acquired it. I've beeb sticking to the factory installs so as to preserve my warrenty for the moment ~ Done: Dinan Chipped, Cool Air Induction, ACS Suspension and lowering, M3 Wheels and am now looking at doing the exhaust.

The question... Well, I've heard some pretty wild stories about removing the CAT regarding horse power... and I want to do a little truth testing using a pass through pipe. The two options I've located are one pipe WITH HIGH-FLOW CAT and one WITHOUT... the price difference is substantial. $369 for no CAT, $1760 with HIGH-FLOW CAT. The obvious problem is that with no catalytic converter, the "check engine light" will remain displayed and I've heard the car may run poorly. Additionally, if you DEQ the car, this will immediately be reported because one of the O2 sensors is not within reason of the second one. Anyone done this before and/or figured out a way to essentially fool the sending and recieving unit into thinking that the o2 sensor's are working properly?

[edjack]

Since you have a Dinan chip, why not ask them if it's worthwhile to replace the exhaust? Unless you're going racing, I believe that it's a waste of money to replace the exhaust system, since BMW did a pretty good job of designing it in the first place. Remember, Germans drive LOTS faster than we do. The cars have to be designed for autobahn performance. Unless you heavily modify the engine (cam, heads, headers, etc), I doubt you'll be able to measure much of anything on a dyno by replacing the exhaust system, certainly not enough to justify the expense.

[kmay]

I don't know if anyone makes them for BMW but there is a company named Dalllas Mustang that sells "MILS" for mustangs so you can run your exhaust without cats.You might ask them who makes them.Just my .02 but the amount of horsepower gained would definately not be worth buying the high flow cats.