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348 catalytic convertor

Discussion in 'Technical Q&A' started by ShanB, Jan 20, 2004.

  1. ShanB

    ShanB Formula Junior

    Jul 9, 2003
    547
    Tejas/Europe/Desert
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    shanb
    I haven't looked up the business end of too many convertors but thought someone could tell me if these look normal. They are shots of the insides with thermocouples in place. Thanks.

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  3. ShanB

    ShanB Formula Junior

    Jul 9, 2003
    547
    Tejas/Europe/Desert
    Full Name:
    shanb
  4. ShanB

    ShanB Formula Junior

    Jul 9, 2003
    547
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    shanb
    Coming soon - the fun begins...
     
  5. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,284
    Texas
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    Steve Magnusson
    Your cats are definitely bad (but don't look too horribly blocked up so you wouldn't notice a runability issue) -- the 400 cell/square inch catalytic substrate should be 1-piece and fill the whole internal diameter (at the inlet side of the cat, just downstream of the O2 sensor). The "steel wool" looking stuff is what should be packed between the OD of the catalytic substrate and the ID of the outer steel casing of the cat (holding the ceramic substrate in place yet providing some cushioning and allowing for thermal expansion).

    In the lower photo (Post#1), the catalytic substrate has fractured and some of the major bits + the steel wool have migrated to the exit side by the thermocouple. On the other one (Post #2) it looks like the some of the (round) catalytic cell substrate is still in the proper place at the inlet, but there shouldn't be any pieces missing (looks like you've got a smilely face). Since some of the supporting steel wool has moved to the outlet it probably isn't healthy either (can't really tell from the photo).

    You can go ahead and completely remove any remaining substrate chunks and the "steel wool" (essentially making them test pipes) without any economic downside IMO.
     
  6. ShanB

    ShanB Formula Junior

    Jul 9, 2003
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    Thanks Steve. I used a borescope to get a good look inside and it appears the catalyst had mostly disintegrated all the way through (there were even a few loose pieces in the exhaust can) The steel liner was loose and blocking the cat outlet. Some digging and pulling now I have a test pipe.
     
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  8. kenyon

    kenyon F1 Rookie

    Oct 7, 2002
    2,836
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    Justin Kenyon
    Take the cats off and get test pipes fitted.
    The runs better more BHP, better engine noise and not issue with cats over heating or cat ecu's warning lights coming on...
     
  9. ShanB

    ShanB Formula Junior

    Jul 9, 2003
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    shanb

    What's the difference between a hollow cat vs. a test pipe? Are you saying I'd still be better off with test pipes even now that I've "cleaned out" the cats? Just trying to understand.

    Thanks.
     
  10. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
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    Rob Schermerhorn
    Those are way past their prime. You should replace them to maintain emissions compliance. OTOH, I doubt there's much flow difference between gutted cat housing and straight exhaust tubing.

    This example is why Ferrari and other manufactures changed to more robust construction of catylist matrix as soon as the technology improved. F355 and newer have the updated material.

    Best regards,

    Rob Schermerhorn
     
  11. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,021
    A test pipe of the diameter of the header output just flows exhaust gasses.

    A gutted cat has an expansion area and a convergence area. The expansion area will help the header send a negative pressure wave up the header to help exhaust scavenging. The converging area will send a positive pressure wave up the header to push any mixture pulled into the exhaust back into the combustion chamber during valve overlap. Get these two things sized correctly, and it operates like a collector.

    I think the gutted cat as a collector is a little short to operate as a real collector, but if the F348 has not too much valve overlap period, it just might work OK (not great but OK.)
     
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