Has anyone knocked out cat. converter?

[bignate]

My cat. sounds like it is cracked so I was thinking of just knocking it out to get free flow all the way down. Has anyone done this before?

 

[mjbst111]

i hollowed out my old jetta's cat. Just knocked out all the ceramic. Still passed emmisions but thats always a gamble.

Could be completely different from state to state county to county, bmw and jetta. etc.

 

[german-speed-demon]

here's the scoop:

If you hollow out your cat, you'll have to deal with the noise factor. Also, to really hollow it out to where the exhaust flow makes a difference in perofrmance, you'll need to take it off and cut the top off to remove the interior, then weld it shut again. in the end, the difference is negligible, but the sound is pretty sweet depending on the state of your exhaust system.

 

[ldzpstnr]

Hey.

It wont be noisy. I had a '85 318i with no cat and it was not loud at all. It had a stock replacement exhaust system and a header also. But wow did the car run better with this set up.

 

[bignate]

Also, to really hollow it out to where the exhaust flow makes a difference in perofrmance, you'll need to take it off and cut the top off to remove the interior, then weld it shut again.

Is this step really necessary? I don't have a welder so this could be a problem.

 

[bignate]

Also, do I have to remove the o2 sensor from the pipe?

 

[mjbst111]

Its not louder and you should be able to knock out the ceramic without opening it.