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exhaust pressure not equal... thoughts?

Discussion in 'Technical Q&A' started by DanielS., Dec 20, 2011.

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  1. DanielS.

    DanielS. Karting

    Dec 13, 2011
    64
    Pleasanton, CA
    #1 DanielS., Dec 20, 2011
    All,

    just picked up my 86 mondial 3.2 and I noticed that one side of the exhaust is flowing fine, while the other side (drivers) is only flowing about 20% of the right side. any thoughts on cause?

    thanks

    D
     
  2. plugzit

    plugzit F1 Veteran
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    Dec 1, 2004
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    Bruce Bogart
    #2 plugzit, Dec 20, 2011
    Bad Cat
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
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    #3 Steve Magnusson, Dec 20, 2011
    Last edited: Dec 20, 2011
    The stock mufflers are asymmetric internally so this is normal behavior for those. If you have a symmetric aftermarket muffler (e.g., Tubi) then that is a problem. Is it running poorly at high RPM?

    Here's an example of a euro 328 muffler cutaway (where the "loud" side is put on the left because the Driver sits on the right):

    Image Unavailable, Please Login

    (US 3.2 Mondial have a shared, single cat so that can't be the trouble -- unless the OP has a US-converted euro where they used 2 cats.)
     
  4. BigTex

    BigTex Seven Time F1 World Champ
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    #4 BigTex, Dec 20, 2011
    I thought there was a slight imbalance (you can see it on cold mornings)..

    But not 80/20?
     
  5. ernie

    ernie Two Time F1 World Champ
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    #5 ernie, Dec 20, 2011
    +1
     
  6. DanielS.

    DanielS. Karting

    Dec 13, 2011
    64
    Pleasanton, CA
    #6 DanielS., Dec 20, 2011
    thanks all. I was thinking bad cat or clogged injectors. I'll check if there is 1 or 2 cats on the car tonight when I get back.

    If only 1 cat, could that still be an indication if one side is flowing less than the other?
     
  7. PV Dirk

    PV Dirk F1 Veteran

    Jul 26, 2009
    5,401
    Ahwatukee, AZ
    #7 PV Dirk, Dec 20, 2011
    One side flows more than the other by design. Don't know ratio. I've put 12,000 miles on my 87 in this condition this year. Runs great.
     
  8. Darolls

    Darolls F1 Veteran
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    #8 Darolls, Dec 21, 2011
    It sounds normal.

    How were you able to make a 20% vs 80% comparison; just by feel?
     
  9. Rossa a nord di

    Rossa a nord di Karting

    Apr 30, 2008
    210
    Barrie, Ontario, Can
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    Brent Pilon
    #9 Rossa a nord di, Dec 21, 2011
    100% agree if car is running well. My 308 is similar when cold but evens out a little after warming up.
    Brent
     
  10. tech4ferrari

    tech4ferrari Karting
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    Jan 22, 2010
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    casey johnson
    #10 tech4ferrari, Dec 21, 2011
    If it is a stock exhaust, it is normal.
     
  11. ztarum

    ztarum Formula 3

    Mar 30, 2008
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    South Jersey, USA
    #11 ztarum, Dec 21, 2011
    That is a great picture. I've always wondered, now I know.
     
  12. davidgovett

    davidgovett Karting

    Apr 9, 2010
    134
    #12 davidgovett, Dec 22, 2011
    I think it starts evening out when you get on road in which case you can't see, feel or easily measure it. One exhaust seems to be the primary and is much stronger than the other during idle. It has been explained to me but I can't remember the details but from everything I have been told, it is normal, provided there is only one CAT.

    Cheers
    Dave
     
  13. Glassman

    Glassman F1 World Champ
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    Apr 23, 2002
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    Montana, Oregon, Hawaii
    #13 Glassman, Dec 22, 2011
    I just ran my car in 28 degree weather. The exhaust on the passenger side was twice the volume on the drivers side. Its been like that since new.
     
  14. mwr4440

    mwr4440 Five Time F1 World Champ
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    #14 mwr4440, Dec 22, 2011
    Since there is no crossover or mixing of exhaust gasses to provide balance,


    I wonder how that uneveness effects performance and / or wear.
     
  15. DanielS.

    DanielS. Karting

    Dec 13, 2011
    64
    Pleasanton, CA
    #15 DanielS., Dec 22, 2011
    excellent, thanks all.

    One item I thought I had to fix is now crossed off the list. On to the next one!!
     
  16. crazyspeed

    crazyspeed Karting

    Aug 11, 2011
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    #16 crazyspeed, Dec 29, 2011
    +1 normal
     
  17. Gordo308

    Gordo308 Karting

    Sep 2, 2013
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    Essex, CT
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    Gordon Laing
    #17 Gordo308, Nov 4, 2013
    Thanks guys. I was just wondering about this too.
     
  18. FasterIsBetter

    FasterIsBetter F1 Veteran

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    #18 FasterIsBetter, Nov 5, 2013
    My 86 328 is unbalanced also. I've never tried to measure the differential, but one side is definitely stronger than the other, and understood that that was normal. I noticed it on my 308 as well, though it had a Tubi exhaust and the difference was not as noticeable as on the 328 with stock muffler.
     
  19. David Lind

    David Lind Formula 3

    Nov 19, 2008
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    #19 David Lind, Nov 5, 2013
    Don't fret! I have an 88 1/2 Mondial 3.2, and its exhaust does basically the same thing. Maybe not 80/20, but nowhere near 50/50. BTW, it did this both in its original exhaust configuration and AFTER I took off the cat and installed a Stebro free flow exhaust. It is not the exhaust or cat IMHO.
     

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