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Replacing cats: straight pipes or resonators?

Discussion in 'Ferrari Discussion (not model specific)' started by Jim Riggs, Mar 19, 2004.

  1. Jim Riggs

    Jim Riggs Karting

    Jan 25, 2004
    85
    I have a 348 SS and I am currently considering removing the catalytic convertors. I have read several past threads on test pipes for 348s, but I am confused about the difference between straight pipes and resonators (e.g., Stebro resonators). Can anyone give me the skinny on this? Cheers, Jim
     
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  3. Dave

    Dave F1 Rookie

    Apr 15, 2001
    2,722
    Little Rock
    Full Name:
    David Jones
    Sure, from what I have heard it is a violation of federal law to remove or tamper with them.
    Not only will you be putting out more pollution,
    but you won't be making any significant HP gains without making corresponding modifications.

    But what do I know...
     
  4. Jim Riggs

    Jim Riggs Karting

    Jan 25, 2004
    85
    Dave-
    I would never consider violating federal laws. I'll only use them at the track. Regards, Jim



     
  5. Dave

    Dave F1 Rookie

    Apr 15, 2001
    2,722
    Little Rock
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    David Jones
    :)

    Jim, most of the resonators I have come across are a little louder
    than just test pipes. That may be somthing to consider if your track has a noise limit set.
     
  6. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,486
    MO
    test pipes are good as they prevent the cat-fire related issues...
     
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  8. gabriel

    gabriel Formula 3

    Greetings:

    Are you talking about street or strip?

    I don't know anything about tracking, but I've used different configurations on the street with my TR.

    As far as federal law, I'm not worrying about the FBI arresting me anytime soon. :)

    There is no emission testing in my part of Florida, for that matter, there is no inspection at all for anything, but anyone that I know using test pipes exchanges them before test time if they are concerned with state mandated testing.

    Mainly, the different sounds are a matter of personal taste, but the 12 cylinders do sound good...

    Keep us posted.
     
  9. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
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    Jerry Wiersma
    I have a TR on it's way to me w/ a TUBI, but no test pipes. What is with the cat/pre-cat thing? Do i want/need to replace all 4? Thx, Jerry.
     
  10. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,486
    MO
    cats are evil things hippies make us add to cars that rob power, add weight and make the car less safe. :)

    If I were you, I would get cat-by passes, and see if a member has a contact with someone who has a good set of cat-less headers.
     
  11. gabriel

    gabriel Formula 3

    Yeah, thats right. Even with test pipes, you will still have the light off catalysts, unless you bore them out, or replace with a euro version.
     
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  13. 92_348ts

    92_348ts Formula Junior

    Jun 6, 2002
    282
    Boise, Idaho
    Full Name:
    Chris
  14. davey_jones

    davey_jones Formula Junior

    Sep 28, 2002
    781
    wherever it's sunny
    Full Name:
    Dave
    Jim - I have a 348 speciale as well.
    Pulling the cats was one of the best things I have done so far.
    It also eliminated some other issues for me as well.
    It's only a couple hundred bucks and an hour or so of work - if you
    don't love the sound... put the cats back on. My guess is they'll stay on
    the shelf for good!

    dave
    indy
     
  15. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
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    Russ Turner
    Put a Stebro resonator on with a tubi. Sorta smoothed out the sound without being louder (surprise). I have heard that naked straight pipes sound a bit harsher.
    good luck
     
  16. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
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    Jerry Wiersma
    What do you mean by "light off catalysts?" Does anyone have a sketch of the TR exhaust system so that I can see what you are talking about? Thx, Jerry.
     
  17. carguy

    carguy F1 Rookie

    Oct 30, 2002
    3,316
    Alabama (was Mich.)
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    Jeff
    TR's exhaust system consists of four 3-into-1 headers coming off the engine, two on each side of the 12 cylinder motor. Then to each pair of headers, the left side and the right side, are the Pre-Cats or Light Off Cats as they are called. These are a "Y" shaped set of pipes that merge the two header collectors into one pipe, one for each side. At the center of the "Y" is a chamber that has some sort of stainless steel mesh in it that creates heat to help the Cats out. Then bolted to the Pre-Cats are the normal Catalytic Convertors, and from there the exhaust flows into the big heavy crossflow muffler, and out the tail pipes. I hope this makes sense.
     
  18. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
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    Jerry Wiersma
    OK Jeff, I think I know what you are saying. So do I need to get rid of the mesh in the pre-cats? Will that make much difference, or should I just get test pipes and eliminate the regular cats? I am after a very aggressive sound. Thx, Jerry.
     
  19. carguy

    carguy F1 Rookie

    Oct 30, 2002
    3,316
    Alabama (was Mich.)
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    Jeff
    Hi Jerry: On my TR I have hollowed out precats and cats with the stock muffler still in place. It's a bit louder than stock but not much. To gut the precats just stick some sort of hook-device in there and start yanking the mesh out. I was a bit disappointed even after cleaning out everything on how quiet the car was. That big heavy muffler has gotta go! So I'm slowly working on my own exhaust system (stainless of course) that will be 4 bullit mufflers arranged in a cross flow position where the stock muffler and cats are now. I'm using the shortest mufflers that I could find. My original plan was to bolt them directly to the headers with simple tail pipes from each muffler out the back. But space is too tight with the under-bumper body panel in place. So I must rethink things out a bit. My system will be similar to the old Borla system that is now discontinued (darn it anyway!).

    If your cats are still in good working order, then test pipes will make the biggest difference in sound, and gutting the precats will help a bit too. But that factory muffler is the big culprit.
     
  20. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
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    Jerry Wiersma
    Thanks Jeff. BTW: the TR that I just bought has a TUBI on it already (no other exhaust mods), but the owner told me that it did not make that much difference in the sound. That is why I am doing some research now as to what is going to make this thing growl. :)
     
  21. carguy

    carguy F1 Rookie

    Oct 30, 2002
    3,316
    Alabama (was Mich.)
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    Jeff
    You lucky dog you! I wish my car had a Tubi....but I'll make the best of it. Test pipes and hollowed precats should make a big difference, and is about as loud as it gets for a TR with Tubi. I've heard that only straight pipes are louder.
     
  22. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
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    Jerry Wiersma
    Thanks for the info. BTW: your project pics are awesome!!
     
  23. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
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    Jerry Wiersma
    OK, Nick's F.F. has the TR test pipes for $658.00/set...is this a good price?
     
  24. gabriel

    gabriel Formula 3

    I really, really like Nick, but the price is HIGH!

    There are two or three members here that make the TR test pipes for under half that. Henryk comes to mind - Do a search in the archives for test pipe. There's a lot in there. Seems like the hardest part was fabricating the flanges and then clocking them correctly.

    Let us know how you make out!
     
  25. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,681
    Texas
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    Steve Magnusson
    Jerry -- The TR pre-cats are labeled #23 and #24 in the illustration below. (If your precats are still intact internally, please give me a shout -- I've got a set with 1 good + 1 gutted that I'd be glad to trade with some $ to preserve a good used set.) I'm running the pre-cat bypass pipes (#57 & #58) with cats and a Tubi and think it gives a good compromise between stock and "loud".
     
  26. gabriel

    gabriel Formula 3

    Steve: I have that manual that you posted, and had noticed those pipes that I believe are euro versions. Where did you get yours? I have a set of intact precats that I'm going to remove within a couple of weeks or so and I'm looking for another setup before I weld up a new system. I'm removing the air pump tomorrow.
     
  27. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
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    Jerry Wiersma
    That's what daddy wanted!!! Steve, if I were gay, I'd give you a big kiss!! :)
     
  28. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
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    Jerry Wiersma
    So with the pre-cat by-pass pipes AND cat by-pass pipes (along w/ TUBI), would you say the car would be border line obnoxious for long drives?
     

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