jsviking08

I have a 2002 camaro z28 and I am thinking of adding pacesetter headers and a catback magnaflow exhaust. I have a few questions about the oxygen sensors and catalytic convertor. I live in Texas so we are required to pass an emission test during inspection. With that being said, I am thinking of going with the Pacesetter longtube headers with O2 sensors holes already in the headers. I am thinking of buying the pacesetter off road y pipe also.
There are a total of (4) O2 sensors, two before the current cat and 2 after. I want to place one high flow cat after the y pipe. Is this possible??

Also what about the 2 downstream O2 sensors? How do I fit those into the new system? I dont want to be driving around with an SES light, it will bug the crap out of me.

Going to use band clamps for all connections.

Injuneer

Anything is possible, but.... why do you want to go from 2 cats to a single cat? Do they do a "visual" inspection? If so, you usually can't pass with a single cat on a car that was originally equipped with dual cats. You are already relocating the cats with long tube headers, which is technically a violation of Federal law, which prohibits relocating the cats, or changing the number of cats. Not all states/locales enforce the Federal law.

Additionally, you will get less pressure loss (= power loss) through a high flow cat in each branch of the Y-pipe, rather than a single cat in the intermediate pipe.

If you go ahead with the single cat in the intermediate pipe, you have three choices for the after-cat O2 sensors: 1) weld bungs for both sensors in the intermediate pipe, after the single cat; 2) get O2 "sims" to eliminate the after-cat sensors and not get codes/SES light; 3) have the after-cat O2 sensors "programmed out" of the PCM to eliminate the codes/SES light.

jsviking08

What would be my options for adding two cats? Would I add a cat between each header and where they attach to the y pipe??

What does deleting the downstream O2 sensors do to the performance of the car?? Where can I get this done? Reasonable price to program out downstream O2s??

Injuneer

You could bolt a cat directly to the collector flange for each header. Then start the Y-pipe immediately after the cat. I used that approach with my 94 after the stroker build - a 3" CarSound cat bolted to each collector, and a custom 3" Y-pipe into a 4" intermediate pipe, using a Flowmaster 3" to 4" merge.

You need to see if Pacesetter makes a Y-pipe that incorporates the two cats. I know Kooks and SLP have dual-cat Y-pipes for 98-02 F-Bodies. I found this one at Texas Speed - says it fits Pacesetter:

https://www.texas-speed.com/p-292-te...ed-y-pipe.aspx

jsviking08

This looks like a great way to go. I think I will do the texas speed 1 7/8 headers with Texas Speed catted y pipe.

What does deleting the downstream O2 sensors do to the performance of the car?? Where can I get this done? Reasonable price to program out downstream O2s??

I am looking to upgrade the car to about 475-500 HP (via Texas Speed Stage 1 Heads/Cam) will I have any issues with this proposed exhaust setup?

jsviking08

Also, Can I keep my stock cat back exhaust or should I upgrade new cat back??

Injuneer

If you keep the cats, you keep the after-cat O2 sensors. The only purpose they serve is to verify the cats are in place and working. No significant effect on performance.

For a 500 (flywheel??) HP setup you need an upgraded cat-back system. You might want to look at the Mufflex 3-1/2" catback with a owmaster single out 30-series race muffler, or the SpinTech dual outlet muffler. If you want to stay 3", look at the SLP Loudmouth.

jsviking08

Thank you for all the help. It has helped me a lot. I just bought my magnaflow catback exhaust.

I think I have decided to go with the American racing headers and catted y pipe in about a year. They are a little more expensive but from the reviews I have read, they seem to be good quality and little to no issues on install. All the original OEM exhaust equipment are easily bolted onto these headers.

I was thinking I should weld all the piping together except for the CATS just in case I need to change out the CATS in the future. I will use band clamps for these 4 pipe connections (2 on each cats).

Any thoughts??