I was wondering if anyone replaced their cat w/ a straight pipe and if so could you tell a difference at all. I was thinking about doing this instead of a high-flow cat.. And yes I know this is illegal. Thanks guys

 

I did. Its a "racing" cat. Noticed the improvement at high rpms.

Similar to header gains IMO.

I like knowing my header wasn't being restricted and the entire exhaust stream is now free flowing.

Check my site for comparisons between the old cat and the pipe.

BTW you'll have to do something for that second O2 sensor (sits in the cat).

 

I think the difference is so minimal that it's not worth the risk. I had straight pipes leading to 2 chamber flow's in a dual exhaust setup with a Chevy small block. The dyno showed about 1.5 max hp increase throughout the RPM band. That's on a motor that put out over 400 hp. Oh, the pipes were 3 inches also. So with those numbers in mind, I don't think you'll see any more than .5 hp increase. Is that worth the risk of an EPA ticket?

That being said, it makes your exhaust louder

 

Thanks fellas, Ill keep that in mind.

 

My racing cat made by OBX (which is str8 thru) made a noticable difference top end wise but it did not make the exhaust, engine or anything else any louder at all. Heres a pic of mine: