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need advice on high flow cats

This is a discussion on need advice on high flow cats within the General Help forums, part of the LSx Technical Help Section category; I just lowered my car a few weeks ago and my exhaust hangs really low. I have full slp exhaust,LT's,ORY,high ...

  1. #1
    Member BRANDON's Avatar
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    need advice on high flow cats

    I just lowered my car a few weeks ago and my exhaust hangs really low. I have full slp exhaust,LT's,ORY,high flow cats,and loud mouth,long story short,due to some road construction i ran over a chunk of the road or something and crushed one of my cats and dented up my y-pipe,my question is should I replace the cat or leave it off and take the other one off?? they do not check emissions where i live so i dont have to worry about that,my other concern is if i toss em there will be nothing but the resonator left so does there need to be any back pressure? my car has about 500hp.

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    I am confused. An "ORY" is an off-road Y-pipe which omits the cats. But you posted that you have cats installed on the system? Where?

    To answer your question, consider modifying your system for better fitment, or upgrade to a Kooks Y-pipe or something that fits better than SLP.

  3. #3
    Member BRANDON's Avatar
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    the cats come directly off the headers to the y-pipe,i said ORY because thats what slp calls it,when i bought the exhaust system the guy told me he would recommend i get the cats because theres not much back pressure with the loudmouth system without them,but he could have just been trying to up-sell me,so will my engine be fine without them?? the only good i can see from having them is quieting down the exhaust some because it is still very loud with them on,the good if i can get rid of them-more hp & more clearance

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    Smiles for 9.5 Years cammed goat's Avatar
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    Your car will be louder without the cats and you will get a check engine light. You could get some slip fit oval cats to replace the ones you have, assuming you have round "spun" cats.

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    Former Mopar Man 2002ssslp's Avatar
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    I have the same system. SLP headers, 2 high flow cats, 3" Y-pipe ging to a CME. I love the system and I feel it is worth the money to replace the cat. I would leave the Y pipe alone.
    My ride is a 2002 Camaro SS SLP #3296 with 30k, LTH, 3" Y, CME, Frost tune, K&N, ported TB, Blackwing lid, Bellows, MSD, Denso Iridium, and 85mm MAF, Bilsteins, Eibach springs, SLP strut brace, Adj. Panhard, TA Girdle, UMI, Pro 5.0, Nitto NT555
    My wife has a 2004 GTO with the rare SAP, 18" wheels, K&N Cold Air System, MSD, Ported TB, Frost tune, Denso Iridium, Flowmaster cat-back, 3200 Yank, 75k

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    Member SuperSSguy's Avatar
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    Depending on how bad the crush is on the cat / y -would determine if you should r/r them? If its a little dented and it doesnt look like you have any exhaust gas restrictions I would lean towards leaving it (unless you have the money then r/r it!) As far as back pressure and keeping the cats most members dont run cats and if you get them tuned out then your ok,except you say your worried about the noise level? I run Kooks Y and Kooks hi-flow cats (because i have to for emissions) but if i didnt have to i wouldnt! I agree with Jeff about the KooKs fitment-mine are a snug fit. P.S. If you do r/r the cats dont throw them away-you can get a little extra $$ at the metal recycler and also check for replacement cats @ Catco- i got a good price for some i have that are Ca. emissions legal for when that ''someday'' comes and i have to r/r/ my non-conforming hi-flows.

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    Member BRANDON's Avatar
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    the cat is definitely crushed,i can hear the stuff inside it rattling around and also the car sounds different,i can probably live with the y-pipe it just has one dent but the cat either needs to be replaced or deleted,i do like the system the way it is so ill probably get a new cat but im gonna have to take it to an exhaust shop to see if they can tuck the system up a little for more clearance,also i thought about deleting the two cats and just putting one cat at the rear of the y-pipe if that will work,thanks for the input guys!

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    Senior Member kingls1's Avatar
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    I did not put cats on my system and it has a raspy sound at around 3,000 RPM's..others on here have complained of the same problem! So with that being said Iam putting the cats back on, I will be going with the Magna Flow spun high flow cats. Look to be about $80ea. from a lot of different places

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    Member SuperSSguy's Avatar
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    Quote Originally Posted by BRANDON View Post
    the cat is definitely crushed,i can hear the stuff inside it rattling around and also the car sounds different,i can probably live with the y-pipe it just has one dent but the cat either needs to be replaced or deleted,i do like the system the way it is so ill probably get a new cat but im gonna have to take it to an exhaust shop to see if they can tuck the system up a little for more clearance,also i thought about deleting the two cats and just putting one cat at the rear of the y-pipe if that will work,thanks for the input guys!
    Yeah if its rattling around thats a pretty good indication of a damaged cat....just replace it!..as far as the Y pipe the muffler shop should be able to fix the dent in it. as far as the one cat at the rear of the Y to me that would be a choke point -like you said you liked the system the way it was-id put it back the same way then.

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    You can use a stud gun and a slide hammer to work out the dent in your pipe. You'll just have to heat the metal with a torch around the perimeter of the dent due to how thick it is.

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    My car has around 630HP at the crank. I do not run cats. It will be fine.

  12. #12
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    Agreed. You can run with or without cats (unless clogged/damaged) for the life of your engine without any ill effects.

    Removing the cat will free up some exhaust flow.

    Don't look for huge power gains on the but dyno but still good over all for your engine without them as they are a restriction.

    You'll get a rear 02 sensor code upon removel.

    Rear 02's play no role in engine performance and will have no ill effect on how your PCM operates the engine.
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    Member Guerrillakilla13's Avatar
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    Subscribed; just found out today that my drivers cat has a horrible rattle problem on startup; at least I think that's what it is. Then again my SES light has been on for months because of a bad cat. Would like to hear from all of you what a great cheap high flow cat would be.

    Jon your putting down 600+ HP???? What do you got in that thing??? lol

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    Member SuperSSguy's Avatar
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    I have KooKs dont remember how much but i doubt they are cheap-Magnaflow along with other brands posibbly even Summit have high flow cats. Also make sur the rattle is coming from inside your cat and that its not the heat shield around it(if yours has a heat shield)

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    Moderator 35th-ANV-SS's Avatar
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    Quote Originally Posted by Guerrillakilla13 View Post
    Jon your putting down 600+ HP???? What do you got in that thing??? lol
    . Threw a blower on it.
    It's on jackstands.

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