jturkel

if you replace the primary cats, what kind of precautions must be done to prevent getting a CEL?

SilverBulletAMG

Where you live depends on how tricky of a fix you will need. In AZ I wouldn't think you would need to be a careful as in CA.
I didn't do the work myself so I can't give specifics but, the shop I had mine done at said they moved the probe back some. Not sure how far but I haven't had any issues. I believe there are a few threads on this forum that give tips and tricks as well. There are plugs you can purchase online that are supposed to eliminate issues as well.

pointman

Nice, thanks Bullet.

ScottW911

Glenn,

There are a ton of threads on this with sound clips, within the C32/C55 forum. You should expect to only notice the sound difference when accelerating. I describe it as a "growl", not a rumble (afterall, this is just a V6). The interior sound at freeway speed does not seem to be affected.

It is the only real mod I've done and I love it. Cheap, quick and reversable. Although, I don't know of anyone that has wanted to re-install the resonator once it was deleted.

calimax

You will need to find a local dyno to go into the ECU and shut off the error code for the primary cat malfunction/below threshold codes. You will more than likely get this CEL since the aftermarket cats that you might be running have far less material or cells to give off the "catalyst" the O2's read. I've seen this many times when I worked at AutoZone. People bought cheap universal cats and came back with a CEL stating that the cats are operating below threshold. That happens when a stock cat is between 500-800 cell or more, and you swapped it to a 150 cell. As for emissions, the rules here recently changed. No more sniffer test, just plug into the OBD2 port. I'm not sure if their test includes any values from the ECU about the O2 readings like the old tests that showed how many carbons, nox etc.. otherwise the test might fail if their not getting any readings from the O2's. I'm not 100% on this, so good luck with it!

Also, you may get different O2 sensor trouble codes as well, like to rich/lean, signal too high, voltage or OHMS to high, etc..

calimax

that would be another trick to use when going the cat-less rout. A spark plug non fouler has been drilled open and stacked to allow the O2 sensor to get less readings due to it not being directly in the exhaust stream. that does work on some cars.

calimax

I would just be concerned with the hole idea of tricking O2's or shutting them down for the monitored cats unless I were using a wide band O2 and monitoring the air/fuel ratio. I don't want to take a chance of going too lean for some reason, and the ECU not knowing and not making a proper adjustment to compensate.

calimax

there are no O2 sensors monitoring the secondary cats. Only one directly before and directly after the primary cat on each side.

pointman

Thank you!