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Removing cats

Discussion in 'Engine/Tuning' started by Blackwell808, May 2, 2021.

  1. Blackwell808

    Blackwell808 Member Established Member

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    Hey everyone, will I need to be retuned if I remove my cats? The car has an ARH longtube system but id like to remove the cats for a little bit more flow and loudness. Magnaflow mufflers will still keep a good tone and not stupid loud. But I do not have any down stream sensors. I have my up stream and afr sensor and that’s it. So technically it shouldn’t need a retune correct? Feel free to correct me if I am wrong. Thanks!
     
  2. shurur

    shurur Well-Known Member Established Member

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    Not to pick a fight or anything, but I am having a hard time understanding why removing cats from a very good exhaust setup is all that important to you.

    Also IMO with the EPA clamping down on exhaust systems, you are asking for trouble..inspection or not.

    I guess you could cut them out and clamp on straights to see what it sounds like. My guess is that you are not going to like it, as the cats act as resonators and are part of the sound, not just part of the loudness.
     
  3. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    When I installed long tubes
    I got matching hi flow cat pipe

    Was quiet

    I than got the off road matching pipe.

    Off road woke up the exhaust but
    It also woke up the throttle response


    I kept every part for if any reason to go back. Even all the stock parts that came off
     
    *Jay* likes this.
  4. Blackwell808

    Blackwell808 Member Established Member

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    Because to me, cats are somewhat restrictive and unnecessary. The car is insured as classic anyways so EPA can’t technically do shit about it since I’m exempt from emissions on it. I’m not dogging the setup I just want the car to be a touch louder. I don’t think cats are what set the tone but more the mufflers dictate that. I would keep my current pipe and have a complete new x pipe made custom
    fo
     
  5. 01yellercobra

    01yellercobra AKA slo984now Established Member

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    There have been dyno tests that show cats aren't as restrictive as people think. At least the high flow cats. And cats do affect sound. They're essentially a small muffler.
     
    shurur likes this.
  6. Blackwell808

    Blackwell808 Member Established Member

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    And that’s part of my point to the post here. I want the car a touch louder but not drastically. I know if I switch to slp or borla it’ll probably end up being too loud
     
  7. 909venm

    909venm Well-Known Member Established Member

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    Cats even a single set like you are using make a massive difference in volume. Unless they are the full body magnaflow’s aka the “street” system it is going to be loud. Mine are only slightly quieter than stingers were on my catless setup. But i run factory manifolds.
     
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  8. Blackwell808

    Blackwell808 Member Established Member

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    Not sure what my magnaflow are exactly but the size of the muffler itself is fairly big. But again would I need a retune?
     
  9. 909venm

    909venm Well-Known Member Established Member

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    Someone will correct me but I believe you would need one. I know on a otherwise factory car simply removing the cats makes it leaner (or richer? I forget) and is why people say to get a tune. If you have a wideband theres no harm going and giving it a test run.
     
  10. Blackwell808

    Blackwell808 Member Established Member

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    I do have wideband luckily. It’s not something I’m in a rush of doing. More of just tossing the idea around
     
  11. OSU34

    OSU34 Active Member Established Member

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    No you do not need a retune. Your upstream sensors are adjusting everything - anything after that (if they are turned off) it doesn’t matter.


    Sent from my iPhone using svtperformance.com
     
  12. cj428mach

    cj428mach Well-Known Member Established Member

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    O2 sensors don't do anything for WOT though which is where you need AFR correct. Although I agree, you won't need a tune other than to turn off an SES light.
     
  13. 13COBRA

    13COBRA Resident Ford Dealer Premium Member Established Member

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    It'll stink.
     
    shurur and Lambeau like this.
  14. stangfreak

    stangfreak Well-Known Member Established Member

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    The epa doesn't care if its a classic or not. They are going after everyone
     
  15. stangfreak

    stangfreak Well-Known Member Established Member

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    If you are building a high hp car, question is, how long with those cats last under high boost. and how many will you be replacing.
     
  16. biminiLX

    biminiLX never stock Premium Member Established Member

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    To answer the OP question, with free flowing exhaust and the rear/downstream oxygen sensors inactivated, no retune necessary.
    May want to datalog or check WOT A/F and even see if boost effected (might decrease up to one full pound).
    I actually think full aftermarket exhaust with cats sounds deeper. Removing the cats definitely makes it louder as it serves as a mini muffler. Only reason I prefer free flowing exhaust on performance applications, especially if boosted, is eliminating the risk of clogged/melted/failed cats.
    I think the stink if no cats is much worse on pump 91/93 than Ethanol.
    Good luck
    -J
     
  17. 9397SVTs

    9397SVTs Well-Known Member Established Member

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    I agree.

    With my Cobra, all I smell is.........
    images(97).jpg
     

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