Exhaust System!

[SmokyJay]

Im planning on putting a new performance and want to remove my cats going straight pipe. The problem is that if i remove the O2 sensors after the cats my check engine light will come on and the car will run on limp mode. And if i make a hole to thread them on then they will receive all that straight fume and make the car run lean, correct me if im wrong. So have any of you guys who has done this please tell me the correct way to do it, appreciate your help. Some guy told me about making tiny side compartment like tubular for the O2 sensor to sit in there so it won't get hit by all the fumes, is this a good idea???

[flyfishvt]

Why dont you just go straight pipe after the cats?

[SmokyJay]

I hate cats!!!!!

[garf]

Just get high flow cats, you don't really gain any performance from removing them, and the factory cats are pretty high-flow from what I've read.

[MrSpectre]

There is a noticeable increase in topend IMO although it's questionable as to if it is worthwhile

[bimmerkid305]

just get o2 simulators

[MrSpectre]

I cut my stock cats in half and gutted them and had them rewelded and I get no CEL which is awesome!

[driftedtofu]

I hate cats!!!!!

I know right! Dogs are wayy better!

I also doubt its really worth the pain this may cause you in the butt in terms of power. You'll probably be getting single digit hp gains.

[sikdogg]

I cut my stock cats in half and gutted them and had them rewelded and I get no CEL which is awesome!
I've read articles in import rags where they compared a hollowed out cat versus a straight pipe on a dyno. The result was that the hollowed out cats lost power due to turbulance in the cat chamber.


... The problem is that if i remove the O2 sensors after the cats my check engine light will come on and the car will run on limp mode. And if i make a hole to thread them on then they will receive all that straight fume and make the car run lean, correct me if im wrong...
I believe that the front o2 sensors are what controls AFR... the rears will cause a CEL but shouldn't make your car run lean.

[SmokyJay]

I want to do it because of the sound its more real, the rear O2 sensors do control mixture. One of mine went bad and there was a strong smell of gas like paint thinner coming out the exhaust meaning it was running rich, when I replaced it the smell went away. Where can I get O2 simulators for my 1998 328i???

[DB MAXX]

doesnt post-cat o2 sensor just control the fuel ratio for open/close loop?
i never heard of a car going in limp mode b/c the post-cat sensor is sending voltage out like the pre-cat sensor. it should just throw a CEL light, nothing else.
just to get off topic...good thing my car is pre-1996. OBDI FTW with Str8 Pipe. which i havent done b/c of emission testing in texas....gay. im moving back to florida.