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Will a cat work AFTER a muffler? (Emissions?)

Discussion in 'The Garage' started by y5mgisi, Feb 6, 2004.

  1. y5mgisi

    y5mgisi 1 ton status

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    1.I have been running without a cat now for a while /forums/images/graemlins/ignore.gif, and now my tags are up. I need to get one in there, But it would be a pain to put one in in front of my muffler. However it would be easy to put one in there after the muffler (about 3'-3 1/2' away from the colecter) Would this stil work to pass emissions test? Or will it not get hot enough to make it work properly.

    2. Also anyone know any tricks to help it pass the sniffer/dyno test? (1990 3/4 ton sub with 350TBI 200,000 origanal miles.) /forums/images/graemlins/ears.gif

    3. Anyone got a good cat layin around?
     
  2. ntaj*ep

    ntaj*ep 1/2 ton status

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    Needs to be as close to the manifolds unrestricted as possible for correct light off.
     
  3. 89BlazerK5

    89BlazerK5 1/2 ton status

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    i had to put 2 cats in mine. just passed the other day. i would put them in in front of the muff. go on ebay and go to the ebay store "performancepeddler" he sells magnaflow high-flow cats for $31.50 best price anywhere. i bought 2 from him.
     
  4. y5mgisi

    y5mgisi 1 ton status

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    Good deal thanks for the tips /forums/images/graemlins/peace.gif
     
  5. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    [ QUOTE ]
    Needs to be as close to the manifolds unrestricted as possible for correct light off.

    [/ QUOTE ]

    I agree with you on this point, but as a counterpoint... When I had my 93 Chevy with a 454, it had the cat after the muffler. This was the stock setup, I am sure. Maybe because it was a big block that it was done this way. Exhaust gets hotter maybe?

    And to the original poster, PM Mudfrog, he sells all kind of exhaust products at extremly good prices.

    John
     
  6. the cowboy

    the cowboy Registered Member

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    Man, it must stink to live in Oregon. I have an 89 3/4 ton Sub, 350 TBI, and run dual flowmaster 60's here. Gettin' rid of that cat really made a difference /forums/images/graemlins/grin.gif
    Those converters need to get hot to work. put it in front /forums/images/graemlins/thumb.gif
     
  7. Goober

    Goober 1/2 ton status

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    [ QUOTE ]
    Anyone got a good cat layin around?

    [/ QUOTE ]


    Free, come by and pick it up:

    [​IMG]

    /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif
     
  8. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    [ QUOTE ]
    Anyone got a good cat layin around?

    [/ QUOTE ]


    Free, come by and pick it up:

    [​IMG]

    /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/whistling.gif

    [/ QUOTE ] /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/waytogo.gif
     
  9. 88Silverado

    88Silverado 1/2 ton status

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    California has some weird laws.
    Technically, your suppose to replace the Cat with a Factory equiv and it must be in the Stock, factory location.
     
  10. bigburban383

    bigburban383 1/2 ton status

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    The cat needs to heat up to work, therefore its got to be closer to the engine. To help pass emissions test, lean out your truck if possible but dont missfire or that leaves unburned gas. I think Gasohol (10% ether in the gas) will help a little too.
     
  11. rodzzilla

    rodzzilla 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    Needs to be as close to the manifolds unrestricted as possible for correct light off.

    [/ QUOTE ]

    I agree with you on this point, but as a counterpoint... When I had my 93 Chevy with a 454, it had the cat after the muffler. This was the stock setup, I am sure. Maybe because it was a big block that it was done this way. Exhaust gets hotter maybe?


    [/ QUOTE ]

    My 93 K3500 w/a 454 has the cat after the muffler, too. Stock set up. Probably won't be there much longer. /forums/images/graemlins/grin.gif Not sure why they did it that way. I had always heard that they needed heat to start working.
     
  12. Silver84k5

    Silver84k5 1/2 ton status

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    [ QUOTE ]
    Man, it must stink to live in Oregon.

    [/ QUOTE ]]

    not if you register your truck in a DEQ exempt area. /forums/images/graemlins/waytogo.gif
     
  13. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    [ QUOTE ]

    2. Also anyone know any tricks to help it pass the sniffer/dyno test? (1990 3/4 ton sub with 350TBI 200,000 origanal miles.) /forums/images/graemlins/ears.gif

    3. Anyone got a good cat layin around?

    [/ QUOTE ]

    I wouldnt use a used cat. If you want to pass, put a new cat on, itll pass, that is if your not horribly polluting. That was always the joke in smog class, if the car filed, heck just throw a cat on it, itll pass!

    Oh and FYI if you have nobbie tires, dont waste your time goin to get smogged, theyll just tell ya to go put some differrent tires on. /forums/images/graemlins/thumb.gif
     
  14. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    How come yall dont just have some cheap exuast made up with a couple cats and some cheapo muffler and as little tubbing as possible just to put on when you go have it inspected?
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    'Cause new cats are almost a non-issue when it comes to restriction. Get a high flowing replacement cat, and you won't notice it's even there.
     
  16. y5mgisi

    y5mgisi 1 ton status

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    Now theres an idea. Two cats?!? would that work? would that be like twice the emissions fixing or would that not work.? /forums/images/graemlins/thinking.gif
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes it can work, but this is the reason you can't add or remove the number of catalytic converters originally on a vehicle...as previously mentioned, cats need to be at a certain exhaust temperature for correct operation. Not sure how narrow that operating range is, but I know it's critical.

    Too close or too far, you change the amount of heat it sees, and how are you going to measure that like GM did?

    On top of that, you are reducing by HALF the amount of exhaust passing through the converter, which means that the heat typically carried from the other bank, would no longer be present.

    I'm not saying you couldn't just slap a couple of them on there and have it put out great sniffer numbers, just that like in head porting, if you do it wrong, you can make things worse. And even if it IS better than original, how do you know placement/operation is optimal, besides lengthy testing?
     
  18. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    [ QUOTE ]
    Now theres an idea. Two cats?!? would that work? would that be like twice the emissions fixing or would that not work.? /forums/images/graemlins/thinking.gif

    [/ QUOTE ]

    Just get one high flow cat and be done with it. Any good exhaust shop worth a thing can cut out the pipe and slap one in there for a good price and make it look good.
     

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