I just put on a new cat back and it's alot louder than I thought. My CEL / ATTS lights are on and the ECU is throwing a P0420 code: Catalyst efficiency below threshold.
If the ceramics inside my cat are broken would this cause my 5zigen exhaust to be louder than normal? Also, when i turn off the engine, I can hear loud pops and crackles coming from the converter. I'm assuming I need a new one. Will this one be okay w OBDII? http://www.mufflertech.com/htm...id=58

I've heard that high flow cats don't work well w/ OBDII. I just don't want to get a new cat and have the CEL come on again.

 

Yes, it would make your exhaust louder. Sounds like you need a new cat. When your car is running at idle, can you hear the converter making noises? I'm not COMPLETLY sure, but I do believe it's true about OBDII not liking high-flow cats.

 

thanks,
That's what i was afraid of.

 

yeah and replacing it will make it less likely for ur o2 sensor to burn out
had that happened to my lude and it was 150 to replace
i'd suggest go oem cat to be safe

 

So, should i get an oem "type" cat, or do i need to get a honda cat?

 

new honda cats are approximately $500.

however, by federal statute, i believe honda has to replace your cat for free if it breaks within 8 years of the car being purchased, as long as the cat's never been altered. they might give you trouble about that, but that's the law, IIRC. you can try taking it back to the dealer (i'd put your stock exhaust on just in case)

as far as OBD2 high flow cats go, stick to the better brands like carsound or random tech, and make sure they're obd2 compliant and they should be ok. if your car still throws a CEL, you can get an O2 sim to get rid of it.