bypass valve 355 | FerrariChat

bypass valve 355

Discussion in '348/355' started by markcoznottz, Oct 7, 2008.

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  1. markcoznottz

    markcoznottz Rookie

    Jan 29, 2005
    43
    england
    Hi folks, my customers car has a rattle, quite noticable now, '95 manual f355 cappy stage 1, tubi test pipes, i think its the valve rattling, question is would 'wiring' it open solve the problem, ie render the action of the valve redundant and save on purchasing a new one?. I know doing this would make the car always loud, more so than before.
     
  2. 285ferrari

    285ferrari Two Time F1 World Champ
    Sponsor

    Sep 11, 2004
    20,958
    MD and NE
    Full Name:
    Robbie
    Not a good idea to wire it open. Some will tell you it is ok, but it is not meant to be wired open and could cause potential problems later on. Capristo sells an aftermarket one that is a much better design than Ferrari. There is also a small adjustment that can be made to the valve sometimes to relive the rattling--A search here will show a few threads on it...
     
  3. DMOORE

    DMOORE Formula 3

    Aug 23, 2005
    1,720
    San Diego
    Full Name:
    Darrell
    Wiring the valve open will not cause damage to the engine. What it will do is trigger the check engine light. Mine has been wired open for years, and the motor is PERFECT. It simply reduces backpressure, nothing more. The only problem is, I have to reset the CEL before a smog check can be performed.




    Darrell.
     
  4. markcoznottz

    markcoznottz Rookie

    Jan 29, 2005
    43
    england
    didnt grahams used to run his capristo with the bypass wired open? he was always on here.
     
  5. Airborne RANGER

    Airborne RANGER Karting

    May 26, 2008
    204
    Lake Tapps
    Full Name:
    Tim
    DMoore: what's the code that comes up- p1448? just wondering.. thinking my car may have been wired open by previous owner. thanks
     
  6. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,044
    USA
    Wiring open on a 1995 car with 2.7 motronic will NOT set a "check engine" light, as there is no thermo probe in the Y section bypass pipe to detect the exhaust temperatures rising and falling as the valve opens and closes (1996 to 1999 5.2 Motronic cars will set a CE light). But, it would be preferable to have it operating correctly, as I think it the jury is still out on possible problems having it wired open could cause long term. First off, you CAN adjust the pre-load tension on the valve, and this can often get rid of the rattle. I suspect it is rattling mostly at idle? Remove the valve from the car, and you will see it has a turn buckle sort of arrangement and you can loosen the nut and add a couple turns of additional spring tension on the valve and reinstall. Try that first. If no luck, you can simply replace it. They are about $1600 for a factory one, or about $950 for the Capristo aftermarket replacement. Note the Capristo works slightly differently, and you have to make a very simple change to the vacuum lines. Threads are posted here on how to accomplish that if you search. I did a write up a few months ago.

    Note also, there are a lot of things that can rattle other than the exhaust valve, to include the heat shields on the Y pipe and exhaust manifolds, along with the heat shields on the catalysts.
     
  7. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,044
    USA
    P1448 Catalyst Bypass Flap Circuit

    Could be a problem with the exhaust valve not working, so you need to see if it may be wired open. Check that it is functioning properly, and if not, inspect the vacuum lines, and solenoid electrovalves (not sure how you test those electrovalves). Also possible the exhaust ECU is bad (that was my problem). You can verify that the exhaust ECU is bad by simply swapping the two plugs that go to it, with the two plugs that go to the exhaust ECU for the right side catalyst. The two ECU's are stacked on top of each other in the right rear area of the bumper, near the air pump. Just remember, you need to move BOTH wires from one ECU over to the other ECU, and vice versa. One plug is for the thermo probe, the other is for the power and signal back to the Motronic.

    Exhaust ECU's are readily available from FoS or Ricambi America. Early exhaust ECU's are black plastic housings filled with black expoxy. The later ones are black plastic housings filled with green epoxy. The later green ones became available during 360 production. They tend to last longer, and the expoxy is less likely to crack and allow water intrusion. But, the green ones still fail, as I have had all green ones on my car since they were replaced in 2003, and one failed last summer, but no cracking of epoxy that I could see.
     
  8. eyboro

    eyboro Formula Junior
    Silver Subscribed

    May 30, 2004
    989
    Chicago
    Full Name:
    Eitan
    What happens if you remove the vacum line from the bypass valve, is it safe?. I read a thread on the 360/430 that it dramaticaly improves the sound (they need sound improvement badly).
     
  9. johan6504

    johan6504 Formula 3

    Jun 28, 2005
    1,168
    Sweden
    Full Name:
    Johan
    360/430 works the other way arround, removing the vacum will make the valve closed all the tima with potential engine problems.

    BTW: In europe we dont have the thermo probe in the Y section bypass pipe and can wire it open without any error...
     
  10. 355

    355 F1 Rookie
    BANNED

    Jan 4, 2005
    3,643
    Toronto
    Full Name:
    Frank
    #10 355, Jun 9, 2009
    Last edited: Jun 9, 2009
    Replace it with the straight challenge pipe and plug the vacume line with a golf tee or small bolt. Part #170683
     
  11. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
    450
    Melbourne Australia
    Full Name:
    Darren Liu
    Yeah, i have a UK spec. car, no thermo probe or third cat ecu. Keeping the bypass open is no problem
     

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