Why Is There A 3rd Cat On My 2011 6.2l?

[MBC Racing]

I noticed what appears to be a 3rd cat on my 6.2L CC 4x4 Sierra. From what I can tell, this is new for 2011. I also noticed that my truck appears to be quieter than 2010 models (most likely) due to this.

 

I am contemplating cutting it off and replacing with a straight pipe or would ideally like to find an off road pipe that bolts to the manifolds. that being said, does anyone know if there is an export only y-pipe that has no cats? Back in the day, I was able to purchase the export pipes for my 96 impala ss. They bolted directly in place of the stock converters.

 

Then I just need HP tuners to release the 2011 software so I would be able to turn off the CEL.

thanks

[Stevens03]

1st closest to the motor is your cat, the next is your muffler, and the last is your resonator

[05GMCZ71]

You can expect to see more than 1 cat in the future with the way the tree hugger communists want it. Crapota's are so dirty some of them have 4+ cats

[MBC Racing]

There is a cat on each side of the motor,and one at the end of the Y. 2010 didn't have that. It looks like it would be a restriction compared to the two big ones in front of it. Anyone have info on it?

[DwayneJ]

I really know the 94-96 b-body platform and can tell you that ditching the cats on that gained you almost nothing. Going to be a similar case on these trucks. You do something that drastically improves airflow into the engine like heads and cam then think about the exhaust.

 

The HP game has become so competitive that OEMs are leaving relatively little room for simple improvement these days, meaningful HP gains means forced induction or engine modification.

[Georgebaumann]

my friend tells me he has a third cat on his jeep grand cherokee because of california emissions before he bought it. other than that no idea

[DaveH71]

Yeah the 2011's have a 3rd cat right before the flex section on the downpipe, mine has it to. There are no o2 sensors behind it so i dont see why you couldnt remove it but you might fail visual inspection if you live in a commie state or just pay off the mechanic like i used to with my camaro

[05GMCZ71]

Yup, for those who have vehicle/emissions testing required, you need to have the number of cats and O2 sensors that the vehicle had from the factory, otherwise you will be a fail

[nickvrebel]

I really know the 94-96 b-body platform and can tell you that ditching the cats on that gained you almost nothing. Going to be a similar case on these trucks. You do something that drastically improves airflow into the engine like heads and cam then think about the exhaust.

 

The HP game has become so competitive that OEMs are leaving relatively little room for simple improvement these days, meaningful HP gains means forced induction or engine modification.

exactly... the cats flow very well and are not a limiting factor on your truck as it sits. you can make a ton more power still before you need more exhaust system capacity. You would first want to open up the flow through the motor with heads and cam. Most "shade tree" special guys are more willing to hack up their exhaust than they are to nut up and do some real engine work, and that is the only reason you see more people chopping off emissions parts that do nothing for their performance.

[MBC Racing]

I really know the 94-96 b-body platform and can tell you that ditching the cats on that gained you almost nothing. Going to be a similar case on these trucks. You do something that drastically improves airflow into the engine like heads and cam then think about the exhaust.

 

The HP game has become so competitive that OEMs are leaving relatively little room for simple improvement these days, meaningful HP gains means forced induction or engine modification.

exactly... the cats flow very well and are not a limiting factor on your truck as it sits. you can make a ton more power still before you need more exhaust system capacity. You would first want to open up the flow through the motor with heads and cam. Most "shade tree" special guys are more willing to hack up their exhaust than they are to nut up and do some real engine work, and that is the only reason you see more people chopping off emissions parts that do nothing for their performance.

 

 

Personally, I don't care for the exhaust sound I get out of a system with cats. Plus the cat over temp feature that you have to keep inabled with will rob you of power when "beating on" your vehicle vs turning it off. I would prefer to quiet my exhaust with a muffler than a cat.

Are you saying there will be no HP increase gained by running an off road pipe vs the current 3 cat system?

[markw8]

Most cats today have little if any restriction to them. Most of the higher out put engines, the cats aren't a problem untill you really up the air flow. Cam, longtube headers things like this. We can thank the factory HP wars for this.

 

Mark