Are CAT's really that restrictive???
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2009-2014 Cadillac CTS-V Performance Mods Discussion, Are CAT's really that restrictive??? in Cadillac CTS-V Series Forum - 2009-2014; I was at a car show yesterday and spoke to a tuner who told me that the main CAT's just ...
  1. #1
    Moparman4444 is offline Cadillac Owners Enthusiast
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    Are CAT's really that restrictive???

    I was at a car show yesterday and spoke to a tuner who told me that the main CAT's just behind the manifolds, where not that restrictive as compared to a straight tube if you were under 620 hp. That seemed completely contrary to every thing I have heard for years. However he said that he had objective data to prove it from 2 cars he tested. I was told that there was less than 3 hp gained with open pipes but a definite sound increase inside the cabin. Those comments made me wonder. Has anyone else ever done a comparison between the stock CAT's vs an open pipe assuming the rest of the exhaust remains the same?

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    ptrd is offline Cadillac Owners Fanatic
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    Re: Are CAT's really that restrictive???

    Coming with no empirical data, I would probably say this is probably true. Maybe back in the day car manufacturers had more restrictive exhaust systems but nowadays with better technology they can push the limits more.

    I know there is a lot of discussion on backpressure (is it good, bad, necessary, etc) and sometimes open headers just don't help as much. I've seen smaller NA motors lose power with bigger diameter exhausts installed.

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    Moparman4444 is offline Cadillac Owners Enthusiast
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    Re: Are CAT's really that restrictive???

    I know from experience that in a NA engine going to a larger exhaust header like 1 3/4" vs 2" can definitely lower hp because back pressure is an important part of the power formula, however in a boosted application, I didn't think that mattered as much.

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    rgp6373 is offline Cadillac Owners Member
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    I don't think being restrictive is the problem with cats, I have has two modded supercharged vehicles (2003 Silverado SS 700+hp and my 2009 Cts-V 640rwhp) and in both the cats disintegrated after a couple months even hi flow cats didnt last, maybe I just have bad luck with them or drive to fast lol

  6. #5
    Moparman4444 is offline Cadillac Owners Enthusiast
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    Re: Are CAT's really that restrictive???

    Generate too much heat with the higher boost????? Nice rgp6373 !!!1 That means your doing something right.

  7. #6
    CavemanB52's Avatar
    CavemanB52 is offline Cadillac Owners Enthusiast
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    I had the same problem. Started melting the stock cats. So I went to Kooks headers no cats. No cats... No problems... little louder than I wanted. Stock muffler but its growing on me. Maybe ill go to Corsa's if it turns out to be too much.

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    rgp6373 is offline Cadillac Owners Member
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    Not to hi jack the thread but with no cats and headers corsa is way to loud, I had to put stock muffler back on. However I did ad QTP cutouts just in front of the mufflers for when I do want to be obnoxious lol
    http://youtu.be/KqbsnTWXA98

  9. #8
    Moparman4444 is offline Cadillac Owners Enthusiast
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    Re: Are CAT's really that restrictive???

    rpg6373, I love the electric cutouts. That is a modern twist on old school trick.

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    What if the CATS were mounted further back like 3-4 feet so they would be in the middle of the car. Granted they would not heat up like if they were closer but would still be emission compliant and would quiet down the car. Just a thought.

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    rgp6373 is offline Cadillac Owners Member
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    That might work but where I live there is no emissions testing so not worth my time or money . Money better spent on gas and tires lol.
    I installed the remote for the cutouts it's nice to have just a little key fob to control them

  11. #10
    6speeder is offline Cadillac Owners Fanatic
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    Re: Are CAT's really that restrictive???

    Quote Originally Posted by Moparman4444 View Post
    rpg6373, I love the electric cutouts. That is a modern twist on old school trick.

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    What if the CATS were mounted further back like 3-4 feet so they would be in the middle of the car. Granted they would not heat up like if they were closer but would still be emission compliant and would quiet down the car. Just a thought.
    Actually, that's not compliant. Compliant means factory cats in factory location. And you might get a CEL because the cats aren't getting hot enough, soon enough.

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    CavemanB52's Avatar
    CavemanB52 is offline Cadillac Owners Enthusiast
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    I almost put cutouts on mine but someone scared me when he said they get stuck sometimes.

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    Naf's Avatar
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    The stock cats are slightly restrictive. Switchin to the high flow will open up top end hp. But u would only do that if u upgrade the headers

    Cutouts are mainly for stock catbacks that are very quiet and power robbin u put them before the mufflers.

  14. #13
    CavemanB52's Avatar
    CavemanB52 is offline Cadillac Owners Enthusiast
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    Again... no cats... no problems...

  15. #14
    Naf's Avatar
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    Naf is offline Cadillac Owners Connoisseur
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    Re: Are CAT's really that restrictive???

    With a supercharger you need some restriction. If you run catless you will gain top end hp but lose on bottom and mid power, (power being hp and torque)

    Put in high flow cats and let the power come to you.

    We dynoed a supercharged car with and without out cats and the verdict was 5 hp gain at max rpm with a 15-20 power loss from 3500-5500rpm

    was it worth it, AH NO!, cut the ac belt if you want more power, we have seen gains of 10hp by simply cuttin the ac belt...

    Ppl will go to extremes to win races here, even if it costs them ac while drivin home after a victory race...

  16. #15
    CavemanB52's Avatar
    CavemanB52 is offline Cadillac Owners Enthusiast
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    The muffler is the only restriction you need to keep from losing HP due to back pressure. The low end HP loss your speeking of is from straight pipes. The test numbers are on this forum. Done with the same car and motor. You are right for the most part but there is no power loss with no cats. There is just not much of a power gain unless over 600 hp or there abouts. So you can't talk generalities. Most who have done more than just added an exhaust ie pulleys, meth, porting will see additional all around improvement with power and torque due to headers. Still need back pressure but a stock muffler to going to provide that. Cats or no cats doesn't make a difference except maybe sound increase. Cats for what they can and can't do is like talking a about purple dragons and wizards.
    Chris09v likes this.

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