Katech L83 Throttle Body

[CamGTP]

5 hours ago, TJay74 said:

 

There is no "3rd" cat on the trucks. You have 2 primary cats and 2 secondary cats. The primary are monitored by the ECM and the O2 sensors, the secondary cats are part of the 50 state CARB requirement. They can be removed with no issues or tuning needed.

 

 

 

 

 

 

I'm going to say you haven't looked under a silverado/sierra/tahoe/yukon since about 2007 with that previous post.

 

There are 3 cats on these trucks, not 4. Vehicles like the camaro/corvette maybe have two primary and two secondary cats.

 

Here is a stock y-pipe.

 

[Black and Blue Z71]

Agree definitely a 3rd cat...

 

[TJay74]

On 2/22/2020 at 9:05 PM, CamGTP said:

 

 

 

 

 

 

 

 

I'm going to say you haven't looked under a silverado/sierra/tahoe/yukon since about 2007 with that previous post.

 

There are 3 cats on these trucks, not 4. Vehicles like the camaro/corvette maybe have two primary and two secondary cats.

 

Here is a stock y-pipe.

 

 

 

And again, that is not a 3rd cat, it is a secondary cat. What you have in that pic is Bank 1 and Bank 2 primary cats and a merged secondary cat. That is the exact terminology for that cat. I have been under a new truck, I own a 2016 Sierra 6.2 and even removed the secondary cat with zero issues. Has been off for almost 2 years now.

 

The secondary cat was forced upon the manufactures by California and the C.A.R.B. act. up until around 2009 GM made a 49 state emission certified vehicle and a California C.A.R.B. certified vehicle for the 10-12 states that follow the CARB program. Then after around 2009 GM started to phase out the 49 state system and move over to a 50 state certified emission system.

When GM made the change it was listed as a 5hp deficit when the secondary cat was put into the system. 

[CamGTP]

Well you did type out that we have 4 total cats, two primary and two secondary so...

 

But I still count 3 cats, so saying 3rd cat still fits the bill if you ask me. Doesn't matter that it's "secondary" to the primary ones, still a 3rd cat.