hollowing out the 3rd cat

[J-Jeezy]

Gutted 3rd cat and the truck sounds amazing. Although my gas Milan stinks now. I'm think about disconnecting the battery and having the truck relearn it's fuel map.

[Archaic2021]

I have my muffler removed. I may do this just to see if I can get a tad more sound from it until I get the coin for headers and full custom built exhaust.

[sourdough44]

Great pictures Desert, thanks.

[2014MallCrawler]

So you noticed the sound increase with the 3rd cat removal?

[J-Jeezy]

Slightly. Now I wanna remove the resonator. But I got a sweet deal on a single in dual out borla setup that I might just go with aswell as a makeshift MIT. I'll keep y'all posted

[K20and2500HD]

when you gutted your cat did it cause any echoing sounds or turbulence with the larger opening of the cat? Just wondering, I would like to do this but not if it makes an echoing sound or sound tinny where the cat is....

[Big_D]

why not just cut out the cat? i didn't lose mileage when a chunk of pipe was welded in place(on my old 2012).. Exhaust got a good bit louder as well. I plan on getting the 3rd cat cut off my 14 soon

[Antoine08]

Might be a stupid question but will this cause a big enough difference to effect me passing smog? Seeing as I live in Cali.

[2014MallCrawler]

Probably, yes. Cali doesnt let you get away with $hit.

[Chris]

Might be a stupid question but will this cause a big enough difference to effect me passing smog? Seeing as I live in Cali.

No it wont. Cali no longer does a sniff test. It is plug in make sure there is no pending codes and pass

[bdbake01]

Just a thought. The 3rd cat does have some effect on the two primaries. It acts as a heat trap to keep the temps in the primaries slightly higher than they would be otherwise. This effectively increases the conversion rate of the primary cats and their efficiency. Conversion rate continues to increase with temperature to the point of sintering at which time the conversion rate plummets.

[Big_D]

Just a thought. The 3rd cat does have some effect on the two primaries. It acts as a heat trap to keep the temps in the primaries slightly higher than they would be otherwise. This effectively increases the conversion rate of the primary cats and their efficiency. Conversion rate continues to increase with temperature to the point of sintering at which time the conversion rate plummets.

Please elaborate... Does this mean leaner A/F ratio? Or would u get less mileage or something?

[bdbake01]

Please elaborate... Does this mean leaner A/F ratio? Or would u get less mileage or something?

Neither really, just higher emissions. A/F is controlled by O2's ahead of the cats. In severe cases it can lower the O2 temps and throw error codes. Our trucks don't seem that sensitive.

[TJay74]

They aren't, GM didn't start adding the 3rd cats until 2009.5 model year. You will be fine as the post cat O2 sensors are only there to confirm the catalyst process is working.

[2014MallCrawler]

i keep going back and fourth about this mod.