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View Full Version : Cat-Less True Duals (Thoughts?)

Arkansaw
09-21-2010, 12:58 PM
I just purchased a 2005 GMC Yukon SLT. I had a faint exhaust smell in the cabin so I ran it by the shop to make sure there were no leaks. It was clear from the sound that an aftermarket exhaust had been installed prior to me purchasing it.

Well, the shop inspected it and found no leaks. They did have some interesting news, though. No exhaust was significantly modified and no longer had catalytic converters.

After I got home I inspected it and found that to be true. The Y-pipe with the cats had been modified to no longer come together. Both cats were removed and replaced with straight pipe with ran into two separate mufflers (full dual exhaust).

This clearly explains why I got the check engine code that my cats were performing poorly. They aren't there!

They installed the post-cat O2 sensor in a bung on the pipe, but since the cats are missing, it will clearly show poor performance from the cats.

So now I need to figure out what I should do, if anything. The exhaust apparently does not leak. It sounds really mean, if a bit too loud. The performance seems solid. Arkansas does not have vehicle inspections so that is irrelevant.

Do I leave it as is and deal with the check-engine light? (which I hate looking at)

Do I install aftermarket high-flow cats?

Do I revert back to the factory y-pipe with cats and kill the dual exhaust system.

Love to hear your thoughts!

Andy

http://farm5.static.flickr.com/4146/5011664795_943524541b.jpg (http://www.flickr.com/photos/onawav/5011664795/)
yukon_sig_strip (http://www.flickr.com/photos/onawav/5011664795/) by On A Wav (http://www.flickr.com/people/onawav/), on Flickr

---------- Post added at 11:58 AM ---------- Previous post was at 11:56 AM ----------

Darn. I just realize I posted in the wrong year section. Please move mods.
stevek
09-21-2010, 01:07 PM
Well if you put cats on, be prepared to spend a pretty penny for two
doubletapdrew
09-21-2010, 01:54 PM
You need to get the rear 02 sensors tuned out otherwise it'll keep tripping the check engine light. An engine tuner should be able to do it. If the shop has a Tech II you may be able to tune them out with that but I am not sure.
That would be the most cost-effective route, as a pair of cats will be $$$$$ and so will a new exhaust setup.

ETA: You could also get some O2 simulators to trick the ECM into thinking the cats are there and working ok.
Zed 71
09-21-2010, 03:55 PM
IMO O2 sims. On the import scene, I have seen some sort of fitting that makes the tip recessed with the exhaust to trick the sensor. For this search test pipes and O2 sensors.
Arkansaw
09-22-2010, 08:23 AM
I'm leaning toward buying a tuner device to make the code not register. I figure if I'm going to have to spend money to fix it, I might as well gain some power out of the deal.

I have a thread open on the Black Bear Performance tuning vendor page on here to see if theirs will tune it out.
sanddperformance
10-01-2010, 04:36 PM
after market cats have came down alot in price
blueflamed03
10-04-2010, 10:19 AM
yep, and does it have true 3" duals, you may have a loss in low end if it does...
Arkansaw
10-04-2010, 10:27 AM
Yes, it does have 3" true dual exhaust. I think I am having a bit of low end loss. I couldn't imagine the exhaust could be any more free flowing than the current setup.

I love the sound, but it is a tad too loud and not quite as refined as I'd like for a Yukon. I'm debating having two quieter aftermarket mufflers put on. I could add cats back in then.
stevek
10-04-2010, 01:06 PM
Yes, it does have 3" true dual exhaust. I think I am having a bit of low end loss. I couldn't imagine the exhaust could be any more free flowing than the current setup.

I love the sound, but it is a tad too loud and not quite as refined as I'd like for a Yukon. I'm debating having two quieter aftermarket mufflers put on. I could add cats back in then.

well, I don't know if your state has emissions testing/state inspections, but if it does, you won't pass. I think you should add the cats back in... it'll make your Yukon legal plus quiet it down and give you the little bit of pressure back in your exhaust
Arkansaw
10-04-2010, 09:06 PM
No.

No emissions checks or inspection here. That being said, I don't really want to pollute more than my large SUV already does. Perhaps I should consider adding the cats back more seriously.

I also hate spending money on something not really broken..