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what are the pros and cons to cutting out my catalytic converters all of them will it hurt my mpg would help it I will mess with my oxygen sensors I currently have a cat back MBRP system with a bully dog GT programmer
 

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Not sure since you have a system, but if I recall other reads, the new engines need some sort of back pressure or else you will lose some not all, some even say its very hard to notice of your low end torque. I was looking at cutting out the muffler and resonator and was told leaving the cats will be enough back pressure. Not sure if this will apply to an exhaust but I believe it might if its a high flow exhaust. Might want to get someone to double check on this!
 

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Get your rear o2s tuned off like me

sent from my Verizon Wireless Galaxy SIII
 

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07bluebeauty said:
what are the pros and cons to cutting out my catalytic converters all of them will it hurt my mpg would help it I will mess with my oxygen sensors I currently have a cat back MBRP system with a bully dog GT programmer
Good info provided already, coming from the race world there were ways around the aforementioned. Just an example on a 5th gen fbody some used a F.A.S.T. piggyback on the PCM with CATS removed and 02 sensors adjusted through a laptop.

While I have no proof, based on my own experiences over the years, the exhaust length on these trucks should provide enough back-pressure to omit any "lack" of back pressure and throwing codes. But, I wouldn't personally go through the trouble and as mentioned already good luck getting past inspection. With my racecars, managed inspections, but it wasn't easy, not my cup of coffee anymore.

I really don't understand the third CAT on my 2011, knew it existed, realize it's extra pollution control, but believe it's another exhaust clog in these trucks. Two CATS are more than sufficient on all vehicles generally speaking.
 

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^im not sure the third one is a true cat? There's been a lot of debate on that one.... waiting on someone to cut theirs off and open!

Ok... so dummy sensors are illegal now the only option is to have your 02s programmed.

Pros to cutting out the cats... well o2 sensor suck and when they go bad they mess up your whole ride... so getting rid of the rear two is like a pm imo lol.

Cats are worth a decent amount in scrap... there be platinum in those things! This could offset the cost of having your exhaust done.

Cons... you'll fail inspection if you live in one of those hippie states that stick a Sniffer up the tailpipe.

The whole backpressure debate is long and complicated... as long as you don't go up to 3" pipe and have a nice muffler you shouldn't really have a problem imo

sent from my Verizon Wireless Galaxy SIII
 

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BravoGolfTango said:
07bluebeauty said:
what are the pros and cons to cutting out my catalytic converters all of them will it hurt my mpg would help it I will mess with my oxygen sensors I currently have a cat back MBRP system with a bully dog GT programmer
Good info provided already, coming from the race world there were ways around the aforementioned. Just an example on a 5th gen fbody some used a F.A.S.T. piggyback on the PCM with CATS removed and 02 sensors adjusted through a laptop.

While I have no proof, based on my own experiences over the years, the exhaust length on these trucks should provide enough back-pressure to omit any "lack" of back pressure and throwing codes. But, I wouldn't personally go through the trouble and as mentioned already good luck getting past inspection. With my racecars, managed inspections, but it wasn't easy, not my cup of coffee anymore.

I really don't understand the third CAT on my 2011, knew it existed, realize it's extra pollution control, but believe it's another exhaust clog in these trucks. Two CATS are more than sufficient on all vehicles generally speaking.
After NOT seeing a sensor on the third Cat, I asked the service guys at the dealer & they said it is there to absorb vibration/flex in the exhaust system.
 

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Being an old-school carb guy (well almost 50 this month), I guess one could say 02 sensor suck, but not really. Thing is we're getting twice the HP these days with less displacement based on design, ie computerized fuel injection, pcm engine/drivetrain dynamic controls, etc.

So 02s are not that bad, most know the pre-CAT 02s work the pcm LIVE once nominal temp kicks in and the pcm goes closed-loop and runs strictly off the 02s. When cold-starting open-loop pre-set parameters run using the MAF feedback and open-loop fuel table to the pcm until nom-temp. When the 02s go bad which typically takes 50-80k miles on these trucks, then you replace them, no biggie. The after-cat O2 sensors are identical to the pre-cat O2 sensors in using the same voltage outputs, but they only to monitor the performance of the catalytic converters. I used to build my own after-cat sensor deletes with resistors, but the main effort are from the pre-cat 02s.
 

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After going through some automotive schooling the way I look at it is this, these trucks were built and designed to have cats and o2 sensors so why mess with them? Unless someone can prove they've had significant gains from removing them I will always just leave the cats in. I pulled the cat off my old D*dge and didn't notice a thing. IMO its not worth it.
 

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Blaine06: I don't have a lot of mechanical training but what you say makes sense. These motors are designed to run with the Cats and o2 sensors. My thought is that simply cutting them out would cause more harm than good. Rebuilding, reprogramming and modifying the motor and every other related system to work without the Cats would likely be required for the motor to run well. This doesn't sound like a driveway mod to be taken up by the novice.
 

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Its not back pressure, it's "exhaust flow velocity". Good exhaust systems are designed so the flow helps scavenge exhaust from the cylinders. The exhaust temp plays a role too. Modifying the system can alter the flow or allow the exhaust gases to cool off too quick and reduce scavenging.
 
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