no cats

[boatpuller]

i was reading thru search results and didn't sound like there should be a problem with my plan.i'd like to get rid of cats and go dual.i don't have to do any emission testing.has anyone ever had a computer problem with doing that?do you have to include any sensors?just like most things you ask about.iv;e got about three different opinion's.i had dual,no cat setup's on computer controled vehicles before without issue's,just not one this new.it's my 05 5.3 silverado z 71.

[droppedgmc]

i don't run any cats and have o2 sims, truck runs great with no probs

[Chevy1972/GMC2000]

I have a 2000 GMC 4.8 with dual and my cats are cooked and are throwing a trouble code so the service engine light is always on. bit if you can delete the sensors there should be no problem.

[john@thepier]

From what I have read on another site about exhaust modifications is that you should have your trucks computer retuned after such mods to get the full potential of the change. I guess air fuel etc is affected from the mods alot more than say the old engines that I'm familar with. I try to learn what I can about my new truck on a site called performancetrucks.net I have been lerking there for awhile trying to learn about my 2002 that I will mod some time in the future. JOHN

[streetstar]

Whaddya mean "no cats?"

[WLPTMP]

there is a chinese rest. down the road from you that is a good "cat eliminator"
hahahaaaaaaaaaaaaaaaaa

[hvychve]

The rear O2 sensors are there to monitor cat efficiency, if the cats are not working or gone, you will get codes for the lack of cat efficiency, there is some reprogrammers that can fool the pcm (powertrain control module- computer)

you just need to find someone that can or will do it, it is tampering with emissions, and regardless if your state mandates the law , it is still unlawful to remove the cats.

[dadsbrew]

It's been my experience that without a re-tune, the exhaust will cool down and the computer will richen the mixture to heat things up making you lose HP and fuel mileage.

[1fun71]

I took the cat of my 91 silverado back in the day, lost a crap load of low end torque. I havent ever taken any off my trucks since, I would say if the engine is stock inside and your not running a supercharger it probably wouldn't be that beneficial, but hey I'm wrong must of the time

[Pyrotechnic]

Correct me if I'm wrong, but won't the gas tank be in the way of true duals ?

One option I've seen people do at the track with these trucks is install dual cut outs before the cats. Your WOT maps aren't affected by the O2 sensor, so it doesn't matter. It's a cheap way to get maximum exhaust flow, but it's only good at the track.

[boatpuller]

sounds easier just to go with a aftermarket muffler or cat back system.

[kevinr1970]

On my '06 GMC the cats are located just after the manifolds; one on each side. On what I would consider the "downpipe".
If you look underneath the pipes come together into a "flange" and that is where the muffler is attached.
My kit attached at that flange, the muffler has the flange welded to it.
It was actually a pretty easy install with mine.

As far as removing the cats, you would have to replace them with pipe in two places. And they are in a kind of out of the way location.
I certainly wouldn't go through that trouble myself for what little gains are to be made. And most shops wouldn't do that for you, or at least can't do it legally.

Another thing, my girlfriends dad (that lives in Kennewick) told me a few years ago that they were pushing for emissions testing statewide by 2010. I never heard about that before then and haven't heard anything since either. It would be worth looking into on your part so you aren't redoing them in a few years.

[dadsbrew]

Originally Posted by kevinr1970

As far as removing the cats, you would have to replace them with pipe in two places. And they are in a kind of out of the way location.
I certainly wouldn't go through that trouble myself for what little gains are to be made. And most shops wouldn't do that for you, or at least can't do it legally.

Another thing, my girlfriends dad (that lives in Kennewick) told me a few years ago that they were pushing for emissions testing statewide by 2010. I never heard about that before then and haven't heard anything since either. It would be worth looking into on your part so you aren't redoing them in a few years.

I agree with the cats, they will only gain you a couple HP, not enough to notice during day to day driving.
Not only are the pushing for state wide testing they are pushing for using California EPA guidelines,