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Thread: Gutting cats

  1. #1
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    Gutting cats

    Hey guys,

    I know I've read it before but during searching couldn't find anything. Since their are 4 cats on a gen 3 I remember reading you can gut 2 of them and still be good for emissions. Which 2 are able to be emptied? I remember reading this helps a lot with interior heat and I'm ready to have a cooler summer!

    Thanks,

    Jesse K.

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    the secondary cats. The ones closest to the muffler.
    Steve A.
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    Scott Grayson
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    Aren't those "resonators"?
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    Thank you!!!

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    Does anyone make a secondary cat bypass pipe for a Gen IV? I know on the Porsche forums this is a popular upgrade and Fabspeed makes them. I would prefer an engineered solution vs. going to have a pipe made at a local muffler shop and having flange alignment issues or vibrations.

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    See... here is the problem.

    The Upstream cats are the ones that the sensors read, that cannot just be "removed". However, these are also the more restrictive ceramic type, more fragile overall, and prone to failure.

    The downstream cats are a very high quality, high-flow metallic type converter. Removing them is almost pointless.
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    The downstream cats are a very high quality, high-flow metallic type converter. Removing them is almost pointless.[/QUOTE]

    I was told Tuesday that removing these secondary cats on a GEN 4 with the Mopar Controller is good for 12 HP. This person is in the know and is flashing my controller. Hence my earlier post.

  8. #8
    Enthusiast Steve M's Avatar
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    Quote Originally Posted by quickster2 View Post
    Does anyone make a secondary cat bypass pipe for a Gen IV? I know on the Porsche forums this is a popular upgrade and Fabspeed makes them. I would prefer an engineered solution vs. going to have a pipe made at a local muffler shop and having flange alignment issues or vibrations.
    Yes, someone does just this, and is what I have installed on my car.

    To be clear, it means you have to replace the entire section...the flex section is removed, there is a high flow cat, and then pipe bent around the corner to connect to the stock muffler.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes, 5-Spokes
    MCS Shocks | Eibach Springs (500/800 F/R) | HPTuners | AEM 30-0300 Wideband | High Flow Cats | Gen 5 Intake Manifold | 11.9 @ 128 (+1000 ft DA)

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    Quote Originally Posted by Steve M View Post
    Yes, someone does just this, and is what I have installed on my car.

    To be clear, it means you have to replace the entire section...the flex section is removed, there is a high flow cat, and then pipe bent around the corner to connect to the stock muffler.
    I have the stock primary cats and plan to keep them. I have decided not to go with Roe high flows and cat back exhaust due to noise. So....I am looking for an "engineered" pipe to eliminate the secondary cats and keep everything else stock. I know a PIA solution.

  10. #10
    NMviper,

    I'm in Abq as well, do you go to C&C on Saturdays?

  11. #11
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    Quote Originally Posted by quickster2 View Post
    I have the stock primary cats and plan to keep them. I have decided not to go with Roe high flows and cat back exhaust due to noise. So....I am looking for an "engineered" pipe to eliminate the secondary cats and keep everything else stock. I know a PIA solution.
    You won't find anything truly engineered, at least not that would allow you to make this a DIY project. Because there is no flange or slip fit connection after the primary cat, you'll have to cut and weld, and that's gonna require someone with a mandrel bender and some time on their hands in order to get it just right. Certainly not impossible, but the cost/benefit ratio just isn't there to justify the effort that would be required.
    2008 SRT-10 Coupe - Venom Red Metallic w/ White Stripes, 5-Spokes
    MCS Shocks | Eibach Springs (500/800 F/R) | HPTuners | AEM 30-0300 Wideband | High Flow Cats | Gen 5 Intake Manifold | 11.9 @ 128 (+1000 ft DA)

  12. #12
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    Quote Originally Posted by quickster2 View Post

    I was told Tuesday that removing these secondary cats on a GEN 4 with the Mopar Controller is good for 12 HP. This person is in the know and is flashing my controller. Hence my earlier post.
    That's all well and good, but it doesn't change the fact that your primary converter is prone to failure anyway, and you would pick up MORE power with an aftermarket truly high-flow assembly... like the secondary that ironically ends up tossed in the trash.

    That said, "WITH the Mopar Controller" is a bit ambiguous to say the least. If that's 12 HP between the two of them, I think we can guess which one is primarily responsible for the power gain. If that's in addition to, well, the Mopar controller wasn't technically needed in the first place for that modification, so I am not sure what you or he may be alluding to.
    Last edited by Viper Specialty; 5 Days Ago at 11:56 PM.
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  13. #13
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    Just to be clear on what I was told. Removal of the secondary cats alone is 12 HP. Not necessarily in conjunction with the controller.


 

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