355 - tube instead of the bypass valve (pictures) | FerrariChat
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355 - tube instead of the bypass valve (pictures)

Discussion in 'Technical Q&A' started by cinquevalvole, Sep 24, 2004.

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  1. cinquevalvole

    cinquevalvole Formula 3

    Feb 6, 2004
    1,161
    Germany, Bayern
    #1 cinquevalvole, Sep 24, 2004
    Last edited by a moderator: Sep 7, 2017
    Hi chatters,

    A 355 GTB guy told me about an torque improvement since he removed his bypass valve
    and replaced it with a simple tube of steel (Version 2.7: 7 cm x 8 cm).
    Guess this part was used in the challenge cars.
    It cannot fail or rattle like the bypass valves do sometimes. Challenge cars
    were always reving higher then 4000/min on the track, so there was no reason for a valve anymore.

    The tube makes sense to me, because the exhaust flow isn't disturbed by any throttle disc.
    The throttle was rather a concession to the legislative then performance enhancement
    as it is selled by the factory marketing. The throttle just allows more performance @ higher revs when it opens.

    By chance I've got that tube now :) It isn't installed yet.
    Who has any experiences with this part? Any challenge riders out there? Should I try it?

    forza

    cinque

    PS: The 512BB on the pictures is scaled 1:43
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  2. jh355

    jh355 Formula Junior

    Feb 12, 2004
    424
    Halluci-Nation
    Full Name:
    Craven Morehead
    #2 jh355, Sep 24, 2004
    I can attest to the increased torque mine has been stuck open quite a few times recently.

    Do not know if there would be problems with the conversion, but another interesting point I discovered when repairing mine. The later year valves had an 8 lb spring on the vacuum canister; the early ones had a 4 lb spring. What this means is the valve opens at approximately 4,000 rpm with the 8 lb spring and approximately 3,200 rpm with the 4 lb spring. A noticeable Torque difference below 4,000 rpm. Another point worth noting is the Air Filters, lowering the restriction also improve low end torque.
     
  3. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    28,991
    socal
    #3 fatbillybob, Sep 24, 2004
    what does the oem smog valve do? If the car is so great with a straight pipe why doesn't ferrari use it all the time? Just curious...
     
  4. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
    Ft Laud
    Full Name:
    Frank Lipinski
    #4 FL 355, Sep 25, 2004
    I wired my by pass open and it is the best DIY project you can do on a 355. The reduction in back pressure makes the car run better and sound better. Loss of low end torque a total non-issue...

    BTW - I was thinking about K&N but seems that they make them for all models except the 355...anybody have a resouce for them?
     
  5. speeder37

    speeder37 Karting

    Nov 18, 2003
    96
    Chicago
    Full Name:
    Matt
    #5 speeder37, Sep 25, 2004
    Cinq.
    Where did you source the steel tube to replace the bypass valve? This is the better way to go compared to wire.
    Speeder
     
  6. cinquevalvole

    cinquevalvole Formula 3

    Feb 6, 2004
    1,161
    Germany, Bayern
    #6 cinquevalvole, Sep 25, 2004
    some clue:

    Sorry, I don't have a source for the tube. It comes from the guy where I got my used Fuchs muffler from. By chance.

    K & N air-filter for the 355:

    http://www.amb-tuning.de/produkte/sportluftfilter/k-n-(austauschfilter)/ferrari/355.html
    They fit to the 456 as well.

    Q: "What can the K & N air filter do to my car?
    A: "They filter the air."
    LOL

    The job of a closed valve is just to reduce the noise level by leading/forcing the exhaust gas through the very silencing parts of the muffler.

    Wireing open the valve is what I did before.
    It was louder but the torque wasn't affected noticeable.
    Now, with 100 cell cats and the Fuchs muffler I have the valve stock position again. Next time I will open it to test the noise level. I won't risk to drive too loud because too many policemen patroling around here :)

    forza

    cinque
     
  7. cal355

    cal355 Formula Junior

    Jun 16, 2004
    383
    San Francisco
    Full Name:
    Cal
    #7 cal355, Sep 25, 2004
    Try Bmc filters.I switched from K&N to BMC.Better fitting around the sealing edges.They are made in Italy and are used by the F1 cars.Uses the same K&N oil and cleaner.(www.bmcfilters.com)
     
  8. cinquevalvole

    cinquevalvole Formula 3

    Feb 6, 2004
    1,161
    Germany, Bayern
    #8 cinquevalvole, Sep 25, 2004
    thanks, any sound improvement with BMC?
     
  9. GeorgW

    GeorgW Karting

    Jan 31, 2004
    103
    Germany
    Full Name:
    Georg
    #9 GeorgW, Sep 25, 2004
    Hi Cinquevalvole,
    around 2 weeks ago there was someone in the german Ferrari board of carpassion.com, who explained that the motronic gets confused if the 355 exhaust valve is permanently opened, because it receives wrong or unexpected data from the kat sensors. Have you read this ?
    Regards, Georg
     
  10. cinquevalvole

    cinquevalvole Formula 3

    Feb 6, 2004
    1,161
    Germany, Bayern
    #10 cinquevalvole, Sep 26, 2004
    Moin moin,

    I only remember this tread:
    here : http://ferrarichat.com/forum/showthread.php?t=28792

    My 1995 2.7 has no temp sensors at the valve and I never had a confused motronic. 5.2 seems to be different.

    Anyway, opening the valve drops the temp in the cats.
    So if higher temperatures were expected by the motronic it can decide to flash the "idiot light".
    REM: cats need a certain temperature to work properly.

    By allowing the exhaust to pass the valve all the time we get higher temperatures in that area
    - especially in city traffic situations with revs under 4.000/min. So what, behind the valve is no part in danger to overheat.
    Policy should always be: Get the heat out as quick as possible in order to save the weak manifolds.

    forza

    cinque
     
  11. GeorgW

    GeorgW Karting

    Jan 31, 2004
    103
    Germany
    Full Name:
    Georg
    #11 GeorgW, Sep 27, 2004
  12. cinquevalvole

    cinquevalvole Formula 3

    Feb 6, 2004
    1,161
    Germany, Bayern
    #12 cinquevalvole, Sep 27, 2004
    Hi Georg,

    now I remember :)
    The guy from the workshop mentioned the simple ring for his 355 challenge cars. Ha!

    The system still cleans the exhaust because in the Y-pipe leading to the valve contains 2 little cats (metal) as well.
    Guess you just misunderstood the way the exhaust is forced to stream:
    valve closed: forced to go through the 2 big ceramic cats with the sensors.
    valve open: exhaust is allowed to run through all pipes and all 4 cats into the muffler (3 pipes instead of only 2)
    This way the 355 2.7 emissions were street-legal since 1994 for the all export countries. My car passes the "EURO 2" norm in germany.

    forza

    cinque
     
  13. GeorgW

    GeorgW Karting

    Jan 31, 2004
    103
    Germany
    Full Name:
    Georg
    #13 GeorgW, Sep 27, 2004
    Hi Cinque,
    now it´s clear: I haven´t had any knowledge about the 2 small metal cats, thanks for the explanation.
    Regards, Georg
     
  14. cal355

    cal355 Formula Junior

    Jun 16, 2004
    383
    San Francisco
    Full Name:
    Cal
    #14 cal355, Sep 27, 2004
    No sound improvement,but the seals of the BMC filters fit better and screw holes line up perfectly.K&N works great but had some problems sealing properly to the air box housing.
     

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