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  1. #1

    Default more exhaust q's

    I have a 2001 Silverado ext. Cab with the 5.3L and would like to know if any damage will come from removing the cats and putting true duel exhaust with a dual inlet outlet muffler and long tube headers. Also how would that affect mpg?

  2. #2

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    There is another post/thread discussing headers that touches on this.... removing the cats will not damage your engine... but just be aware of you local emission laws. The dual inlit muffler will accomplish pretty much the same as a y pipe... keeping the back pressure equal to both sides of the engine. You will need to be sure you install you precat O2 Sensors for ECM... the post cat ones are only really to monitor the efficiency of the cats and does not effect fuel mixture in anyway. Without reprogramming the ecm you are going to get lean codes on bank1 and bank2... and not take full advantage of those new headers.
    2009 Chevy Silverado 2500HDLT 6.0L w/ Towing Package, Dick Cepek GM8 Rims, Dick Cepek FC II 33X11.50R17,RKSport Ram-Air Hood(Functional), Lazer Lite Aluminum Tonneau Cover, Road Armor Stealth Bumper, PIAA Lighting, Diablo Trinity Tuner, Diablew Custom Tune, BullyDog Cold Air Intake, American Racing Headers w/highflow cats, Corsa Performance Sport Exhaust, Custom Striping, Black Bowties front and rear, Fuel Grille Inserts, Recon Headlights, Readylift Shocks, Readylift Upper Contol Arms, 2" Blocks in the Rear..

    Future Plans: HD Tie Rods, Under hood upgrades, Crower Camshaft and possibly electric fans.

  3. #3
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    It will definately affect your LTFT and STFT (long term and short term fuel trims), you are basically moving the 02 sensors further away from there stock position. In order to make it run right your going to need to have it tuned, I have no cats as of right now but I am putting mine back on due to federal laws. I know I'll get flamed for this, but I'll say it anyways. Emissions check or not, your taking federally mandated equipment off of the vehicle. I don't want to take the chance of losing my truck over a set of $140.00 cats from Summit Racing, Truckin magazine just had an article about a guy that got stopped for some violation and the cop decided to look with a mirror under the vehicle. The truck was then impounded, and the owner had to pay a $20,000 fine lol!!!

    Good luck with your exhaust, I am sure it will sound really nice.
    2004 Chevy Colorado
    LS1 5.7 swap/TBSS rear axle swap

  4. #4

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    Like Amy stated this is a federally mandated piece of equipment and regardless of local emissions requirements must be on the vehicle if it left the factory with it.
    Post early 90's vehicles cat. converters don't negatively affect fuel mileage, and the way they've been designed into the system actually helps performance.
    The cost of a new converter will be less than new headers and could potentially save your truck from getting you into legal troubles, it's not much of a stretch for a by the book officer to stop you for something simple, hear the non-stock exhaust, decide to see how non-stock it is, and you end up in trouble.
    I have a friend that can tell a very similar story to Amy's, he's now serving 3 yrs in a penitentiary for failure to pay fines of $65k for multiple incidents regarding mods to his exhaust system. He lived in a very rural county where emissions inspections were not required but he was caught by a roadside drive by check point and failed to respond to official letters that were sent to him.

  5. #5

    Default

    Quote Originally Posted by TimTom64b View Post
    There is another post/thread discussing headers that touches on this.... removing the cats will not damage your engine... but just be aware of you local emission laws. The dual inlit muffler will accomplish pretty much the same as a y pipe... keeping the back pressure equal to both sides of the engine. You will need to be sure you install you precat O2 Sensors for ECM... the post cat ones are only really to monitor the efficiency of the cats and does not effect fuel mixture in anyway. Without reprogramming the ecm you are going to get lean codes on bank1 and bank2... and not take full advantage of those new headers.
    I live in Michigan and my county does not have mandated emissions testing so removing the cats is not illegal regardless of it being put on at the factory. The only thing I would like to know now is how to place the o2 sensors so that everything works right. If im reading your post correctly then all i have to do is move the o2 sensor back past were the cats used to be? And i have a hypertech programmer already would that be able to make the necessary changes to make it run right?

  6. #6

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    Quote Originally Posted by newcheylover View Post
    I live in Michigan and my county does not have mandated emissions testing so removing the cats is not illegal regardless of it being put on at the factory. The only thing I would like to know now is how to place the o2 sensors so that everything works right. If im reading your post correctly then all i have to do is move the o2 sensor back past were the cats used to be? And i have a hypertech programmer already would that be able to make the necessary changes to make it run right?
    Um no, last I checked Michigan was still located in the U.S.A. and as such any vehicle operated in that state must conform to federal standards for the year it was manufactured. Your welcome to debate that point with the EPA if you wish but this has been a law for many years and I doubt you'll get it overturned or a ruling in your favor. Federal law trumps state law, the only reason your county doesnt have emissions testing is because of the population density, but because it doesnt have emissions testing doesnt mean you dont have to abide by federal emissions regulations.

    Heres the EPA website along with a link to the Code of Federal Regulations also detailing emissions compliance and requirements, feel free to check it out for yourself. http://www.epa.gov/otaq/standards/index.htm

    Hate to see someone jam themselves up with the law when the correct information is readily available. From experience I can tell you the EPA's standard answer to "I didnt know it was a law, or required" is ignorance of the law is no excuse, your still liable for compliance.

  7. #7

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    O sorry I didn't look into the federal end of it just the state. So if I get pulled over and the cop takes a glance under and sees no cats will I get a ticket or worse?

  8. #8

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    Quote Originally Posted by newcheylover View Post
    I live in Michigan and my county does not have mandated emissions testing so removing the cats is not illegal regardless of it being put on at the factory. The only thing I would like to know now is how to place the o2 sensors so that everything works right. If im reading your post correctly then all i have to do is move the o2 sensor back past were the cats used to be? And i have a hypertech programmer already would that be able to make the necessary changes to make it run right?
    The O2 sensors you need to keep... Are the pre cat sensors. Place them 5 - 6 inches down from your headers. You can also install the after cat sensors... If your installing the cats I would... This way you'll get away from the trouble code. As I mentioned before the after cat sensors really only monitor cat performance. I don't have any experience with the hypertech programmer so I can't advise you there.
    2009 Chevy Silverado 2500HDLT 6.0L w/ Towing Package, Dick Cepek GM8 Rims, Dick Cepek FC II 33X11.50R17,RKSport Ram-Air Hood(Functional), Lazer Lite Aluminum Tonneau Cover, Road Armor Stealth Bumper, PIAA Lighting, Diablo Trinity Tuner, Diablew Custom Tune, BullyDog Cold Air Intake, American Racing Headers w/highflow cats, Corsa Performance Sport Exhaust, Custom Striping, Black Bowties front and rear, Fuel Grille Inserts, Recon Headlights, Readylift Shocks, Readylift Upper Contol Arms, 2" Blocks in the Rear..

    Future Plans: HD Tie Rods, Under hood upgrades, Crower Camshaft and possibly electric fans.

  9. #9
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    Ticket would be if your lucky, impounded vehicle, federal fine and jail time is worse case scenario. We are just trying to help you. I live in Amish country with no emissions testing either, BUT I still am going to put cats back on mine to make it federally legal. We just finished up an engine swap, that's why my whole exhaust is screwed up at the moment.

    I have a firebird I have been driving with an LT1 long tube headers OPEN, no exhaust at all for the last 2 years because I haven't had the money to get it put on. Next month I'm finally taking it to get it fixed correctly, but It's always on my mind that If I do get caught I will just have to let them take the car and cut my losses and pay the fine.
    2004 Chevy Colorado
    LS1 5.7 swap/TBSS rear axle swap

  10. #10

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    Thanks I appreciate the advice im defiantly going to fit the cats in some place

    - - - Updated - - -

    Quote Originally Posted by TimTom64b View Post
    The O2 sensors you need to keep... Are the pre cat sensors. Place them 5 - 6 inches down from your headers. You can also install the after cat sensors... If your installing the cats I would... This way you'll get away from the trouble code. As I mentioned before the after cat sensors really only monitor cat performance. I don't have any experience with the hypertech programmer so I can't advise you there.
    how far do i need to place the the o2 sensors from the cats im taking your advice and putting new ones on. dont want to risk getting my baby taken away for some stuped reason like that. im new to the high performance end and finally got a truck worth working on.
    Last edited by newcheylover; 01-28-2013 at 10:01 AM.

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