pros and cons on removing cats

Discussion in '2005+ Mustang GT 4.6L Tech' started by Johnstone, Jun 18, 2019.

  1. 07Bossman

    07Bossman Junior Member

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    I understand. Been there done that. But it sorta reminds me of being free from cigarette smoke and then getting a whiff of one and thinking just how vile and abusive it is to the senses. I can smell a 70's truck 5 blocks or more before I even see it.
    There was a time when getting an extra 5 hp out of the old HO 5.0 was worth whatever it took. Now your grandma's 2018 4 cylinder Ecoboost eat that thing for lunch and have room for pie... bone stock.
    I remember the "IF it's too loud, you're too OLD!!" posters as a youth. I'm getting old.
     
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  2. Badd GT

    Badd GT forum member

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    Can’t think of any downside to eliminating the cats. I put some resononaters in there place in the h pipe after the long tubes. No drone and with factory mufflers, American thunders and I can’t remember the mufflers I’m running now, car sounds great.
     
  3. Badd GT

    Badd GT forum member

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    Can’t think of any downside to eliminating the cats. I put some resononaters in there place in the h pipe after the long tubes. No drone and with factory mufflers, American thunders and I can’t remember the mufflers I’m running now, car sounds great.
     
  4. Macman45

    Macman45 Resident Geriatric

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    I'l keep this simple: The primary reason to remove the cats is increase exhaust noise. NOT increase performance. I wanted it loud and love it. Maybe gained a few HP but that wasn't the primary goal.
     
  5. Pentalab

    Pentalab forum member

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    Hi-flow cats are loud too. Zero difference in hp with hi-flow cats... vs no cats.

    Hi-flo cats are far less restrictive..vs oem cats. Hi-flo cats are typ 4" diam.... and short in length.
    More parallel paths = overall less restriction / less back pressure..... but internal volume is the same as oem.
     
  6. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    Eliminating the cats dramatically increases NOx emissions and adds to air pollution. I'd consider that a major downside.
     
  7. fdjizm

    fdjizm Drag Queen

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    Did you have a lemon or something? I'd say my little baby 3v responds veeeeerrry well to bolt on's and cams.
     
  8. Pentalab

    Pentalab forum member

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    Vorshlag Racing measured 447 rwhp on their 2011 5.0 stang.... with just LT's and a 93 tune. That's nothing to sneeze at. No blower required, no extra weight, no IAT issues.
     
  9. MrAwesome987

    MrAwesome987 forum member

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    With what Dyno? HP numbers are worthless without proper testing.
     
  10. fdjizm

    fdjizm Drag Queen

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    1/4 is the real dyno!
     
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  11. MrAwesome987

    MrAwesome987 forum member

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    Exactly!
     
  12. Pentalab

    Pentalab forum member

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    Dynojet in Houston. It was used for road course racing. That's all well documented on S197.

    Five-oh-Brian was down to 11.62 on the strip, with his 2012...no blower..and no LT's. If LT's were installed, he would get booted from the track... come back with the roll cage. That's also well documented on S197.
     
  13. RED09GT

    RED09GT Senior Member S197 Team Member

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    NHRA clarified the definition of "unaltered". Newer than 2008 is good to [email protected]
     
  14. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    IIRC, OEM cats since the S197 era are far less restrictive and flow more efficiently when compared to the previous generation OEM SN-95 cats. At any rate, I'd like to see some actual real-world test comparisons between the OEM S197 cats vs high-flow cats to determine if they're really far less restrictive or just marginally less restrictive :shrug:
     
  15. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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  16. fdjizm

    fdjizm Drag Queen

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    ...or not wanting to blow your motor with clogged cats while using forced induction, a two step or no lift shift with a wotbox.
     
  17. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    I totally forgot all about the Anderson Ford Motorsport exhaust shootout from nearly 14 years ago, so thanks for refreshing my memory lol.

    Well, I find that very difficult knowing that the Shelby GT500, Saleen 281 S/C and Roush stage 2 and 3 models are all forced inducted from the factory with OEM cats. Same also applies to the Challenger Hellcat/Demon that makes over 800 HP. Therefore, I would think if the factory cats were as restrictive as some of the nay-sayers claim? there would be widespread complaints about clogged cats blowing up motors. As for the select few that do end up with blown motors from clogged cats, are usually the result from aftermarket tuners who didn't calibrate the air/fuel mixture properly.
     
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  18. fdjizm

    fdjizm Drag Queen

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    Cats have come a way since the older ones, but I believe if you lay on a two step for too long you can cause enough tiny explosions to obliterate the ceramic based cats. I guess metallic based cats are a different story.
     
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  19. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    I agree about the potential risk of obliterating the OEM ceramic based cats if laying on a two-step for too long, but then again, I can't speak from personal experience as my days racing at the track ended over 23 years ago. But as you brought up, OEM cats have come quite a ways since the older pre 05 models and are far less restrictive. However, when it comes to competitive racing, I'd also recommend going with either high-flow metallic cats or no cats at all in order to eliminate any potential risk :waytogo:
     
  20. datmbn

    datmbn forum member

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    I doubt that there is any difference between "high-flow" cats and original cats!
    This is how it usually gooes:
    Old car (60000 miles) comes in to garage, that will test their high-flow cats:
    The car is tested before changing cats, and then after, and you get a difference of about 3 hp.
    I think you had the same difference if you switched to new oem cats as well
    I think the difference is more dependent on age than on the type.