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Cat delete?

Cat delete?

Postby starspangled6.0 [OP] » Nov 18 2011, 4:17pm

Two questions:

What kind of performance gains are there to be had by replacing the cats with straight pipe? I've got a stock exhaust on, except for my Flowmaster muffler. Eventually, I'd like some long-tube headers, but if cutting off the cats will help the engine breath better, I'm all for it.


If I do cut them off, won't that trigger the check engine light? If so, is there a way to bypass that problem, or just to fool the computer in thinking there are cats still on?
07 Silverado 3500HD 6.6L Crew Cab Dually
04 Silverado 2500HD 6.6L Extended Cab w\Hiniker 8.5 V
03 Sierra 2500HD 6.0L Extended Cab w\BOSS 8.2' V


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Re: Cat delete?

Postby rdss » Nov 18 2011, 4:35pm

It will help flow, it's breathing through two porous rocks on each bank right now. If you would have went with a Diablo Sport tuner either you would have had the option to disable the rear O2 sensors or Lew deffinatley ccould have. Shorty headers and a cat delete is a pretty good upgrade over stock if long tubes are out of the question.
2010 GMC Sierra 1500 SLT Crewcab:
K&N Aircharger
Blastin Bob's muffler back w/ Magnaflow muffler
BedRug BedTred
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Diablo Sport inTune....DiabLew tuned!
Black Rampage sidesteps.
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Re: Cat delete?

Postby starspangled6.0 [OP] » Nov 18 2011, 4:59pm

OK, I like the performance side. Will the 02 sensors cause issues if I don't get it re-tuned by Diablo for a while? I'd love to get one of their programmers and have a custom tune done, but that's not in the budget right now.
07 Silverado 3500HD 6.6L Crew Cab Dually
04 Silverado 2500HD 6.6L Extended Cab w\Hiniker 8.5 V
03 Sierra 2500HD 6.0L Extended Cab w\BOSS 8.2' V


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Re: Cat delete?

Postby rdss » Nov 18 2011, 5:10pm

You will have your check engine light on all the time since the rear O2 sensor reading will be out of spec. I know of people that drive like that but I am not sure if there is any long term by doing this, i.e. the truck adjusts its fuel to try and compensate for the improper reading. I am sure Lew or one of our ASE mech's can help a little more there. By the way, I am pretty sure that other tuners can do this as well and I know Black Bear is more than capable, I just know you were interested in the inTune.
2010 GMC Sierra 1500 SLT Crewcab:
K&N Aircharger
Blastin Bob's muffler back w/ Magnaflow muffler
BedRug BedTred
Extang Revolution Tonneau
Diablo Sport inTune....DiabLew tuned!
Black Rampage sidesteps.
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Re: Cat delete?

Postby adams99z71 » Nov 18 2011, 5:15pm

let me speak from experience.

i currently have no cats on my 5.3. i still get the same mileage as before and you can smell my truck a mile away. also at 180,ooo miles when i took the stock cats off, there was was zero build up inside and i could see daylight through them. the inside kinda looks like the screen on our map sensor just a bit tighter.

i recently talked to one of the exhaust experts at the college (who writes for a certain rod mag). and he explained also that now days with the cats being as good as they are at "filtering/cleaning" the exhaust emissions as they are, engine manufactures build engines that run dirtier than most of the engines built back in the 60's. hence the reason my truck smells stronger than my buddies 67 nova.

on a side note the o2 sensors will not do anything but set a SES light. the down stream o2 sensors only monitor the efficiency of the cats as per ob2 requirements. you can use a hollowed out sparkplug defouler to get rid of the light 19mm i want to say.
nbs99 z71 325ci v8, stock 4wheel disc brakes, no cats, flow master classic 40 series, rhino line, custom fog lights, cb, bully dog tunner, 4:10 locker, airbag load leveling, 205,000miles.
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Re: Cat delete?

Postby rdss » Nov 18 2011, 5:28pm

Defouler's were how they got rid of the lights on my Civic Si before th Hondata tuning software came about. I have always figured it would do the same thing on our trucks, you would just need two of them in the correct size.
2010 GMC Sierra 1500 SLT Crewcab:
K&N Aircharger
Blastin Bob's muffler back w/ Magnaflow muffler
BedRug BedTred
Extang Revolution Tonneau
Diablo Sport inTune....DiabLew tuned!
Black Rampage sidesteps.
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Re: Cat delete?

Postby Gorecki » Nov 18 2011, 8:15pm

FWIW, if low end torque is a factor for you (towing, hauling at lower RPM) the elimination of the back pressure commonly caused by a CAT may cause more harm than good. Again, FWIW. :)
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Re: Cat delete?

Postby starspangled6.0 [OP] » Nov 18 2011, 11:39pm

I tend to disagree with the whole "backpressure saves torque" argument, so this is a good way to find out if I'm right :D! The 6.0 makes peak torque and power really high in the RPM band, anyway; plus I've got a 4.10 rear axle that helps a lot.
07 Silverado 3500HD 6.6L Crew Cab Dually
04 Silverado 2500HD 6.6L Extended Cab w\Hiniker 8.5 V
03 Sierra 2500HD 6.0L Extended Cab w\BOSS 8.2' V


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Re: Cat delete?

Postby Gorecki » Nov 19 2011, 12:39am

starspangled6.0 wrote:I tend to disagree with the whole "backpressure saves torque" argument, so this is a good way to find out if I'm right :D! The 6.0 makes peak torque and power really high in the RPM band, anyway; plus I've got a 4.10 rear axle that helps a lot.



Fair enough, just for your viewing entertainment take a peak at what Arron Johnson has to say. This dude has built more engines than likely most of us will ever touch.

How can I turn my late model GM truck into a power house?

What is the difference between horsepower and torque?
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Re: Cat delete?

Postby starspangled6.0 [OP] » Nov 19 2011, 12:51am

Good info. I've heard "experts" from both sides of the argument... there's only one way to settle this. Hopefully when I get some spare time, I can look into finding a shop that can do it for a good price.
07 Silverado 3500HD 6.6L Crew Cab Dually
04 Silverado 2500HD 6.6L Extended Cab w\Hiniker 8.5 V
03 Sierra 2500HD 6.0L Extended Cab w\BOSS 8.2' V


http://www.integrityoutdoor.biz
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Joined: Nov 08 2010, 9:38pm
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Extra Info: 3500HD 6.6L Duramax
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