cutout before cats
cutout before cats Hi all, I am new to Ls1 world. Coming over from a Dodge truck. I've got a 2000 ss convertible now. Planning headers, etc. I'm going to do long tubes and cutout and retain the cats. I want a cutout somewhere before cats.
I wanted to do a single cutout after the y-pipe... but I see I've got 2 cats and they are way up before the y-pipe. I'd rather not do 2 cutouts... just because I don't want to constantly be replacing gaskets. Can I do a single cat after the y-pipe? Can I even move the cats without incurring the wrath of the emissions people? Do the cats work as well when you move them down the line?
Thanks for the help.
I wanted to do a single cutout after the y-pipe... but I see I've got 2 cats and they are way up before the y-pipe. I'd rather not do 2 cutouts... just because I don't want to constantly be replacing gaskets. Can I do a single cat after the y-pipe? Can I even move the cats without incurring the wrath of the emissions people? Do the cats work as well when you move them down the line?
Thanks for the help.
first off where do you live?
if you put cut outs before the cats where the are now you will get cold air in the o2 sensors and you will run rich.
i dont think you can put a cat that far down past the y-pipe, exhaust gas has to be hott for the cats to work, it wouldnt be efficicient enough and im pretty sure you wouldnt pass a test.
i think the best thing to do it put on high flow cats and put a cut out right after the y-pipe meets.
if you put cut outs before the cats where the are now you will get cold air in the o2 sensors and you will run rich.
i dont think you can put a cat that far down past the y-pipe, exhaust gas has to be hott for the cats to work, it wouldnt be efficicient enough and im pretty sure you wouldnt pass a test.
i think the best thing to do it put on high flow cats and put a cut out right after the y-pipe meets.
That answers that. Thanks. I don't mind the hiflow cats, but it would sure would be cheaper to simply bypass the cats at the track.
I wonder why it didn't cause problems on my Dodge 5.9l engine to put the cutout before the cat? Maybe the difference between a speed density based Fuel Injection system and a Mass airflow based? Maybe the Dodge system didn't adjust fuel based on temp or O2 downstream from the cat?
I wonder why it didn't cause problems on my Dodge 5.9l engine to put the cutout before the cat? Maybe the difference between a speed density based Fuel Injection system and a Mass airflow based? Maybe the Dodge system didn't adjust fuel based on temp or O2 downstream from the cat?
Originally Posted by bigwillie
That answers that. Thanks. I don't mind the hiflow cats, but it would sure would be cheaper to simply bypass the cats at the track.
I wonder why it didn't cause problems on my Dodge 5.9l engine to put the cutout before the cat? Maybe the difference between a speed density based Fuel Injection system and a Mass airflow based? Maybe the Dodge system didn't adjust fuel based on temp or O2 downstream from the cat?
I wonder why it didn't cause problems on my Dodge 5.9l engine to put the cutout before the cat? Maybe the difference between a speed density based Fuel Injection system and a Mass airflow based? Maybe the Dodge system didn't adjust fuel based on temp or O2 downstream from the cat?
yeah i guess the dodge's o2's sensors are further up.
but take my advice with a grain of salt. i still have stock exhaust, i just read a lot
Yeah, had a cutout before the cat on the Dodge. Folks said that the o2 sensor downstream didn't do anything as far as adjusting the fuel. Not sure why it was there. But I never had any problems with the cutout open. Of course, it was never open for longer than a day or so.
Also interesting that the Cat was farther downstream on the Dodge.... in fact, it was just after the ypipe. Is there any year LS1 where there is a single cat used?
Also interesting that the Cat was farther downstream on the Dodge.... in fact, it was just after the ypipe. Is there any year LS1 where there is a single cat used?
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TECH Apprentice
Joined: Dec 2004
Posts: 309
Likes: 0
From: Evansville, IN
I was planning something along these lines for my '02 Z28. I was going to use QTP headers with their dual-cutout y-pipe and place a Random Tech 9000 series cat directly after the y-pipe. So this setup will not work well at all?
