bypass valve

Discussion in '360/430' started by darrenliu, Jun 4, 2009.

  1. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
    Melbourne Australia
    Full Name:
    Darren Liu
    Does anyone know if the 360 or 430 exhaust bypass valves operate via a solenoid or straight off engine vacuum?

    I have noticed that when a 360 or 430 is revved in neutral, the bypass valves open very soon and create a lot of noise, where as with the 355, the engine needs to be revved quite hard several times in neutral to induce the bypass valve to open. I have replaced my oem bypass valve with a capristo one which operates in reverse to the oem one (similar to the 360/430 which requires vacuum to close the valve). I was thinking of plumbing the vaccum straight from the engine to the capristo valve to get a more instant response from the bypass valve.

    Any comments would be appreciated.
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  3. F360-1386

    F360-1386 Formula 3

    Oct 8, 2006
    Markham, ON, Canada
    Full Name:
    I took mine off from the Tubi tips ; it sounds great at all time.
    GCNSX likes this.
  4. SKXF430

    SKXF430 Karting

    Oct 19, 2004
    W. Los Angeles
    The 430's work off vaccuum. Just unplug them and cap off the loose end on the hoses for more noise all the time.
  5. gages

    gages Karting

    Jan 5, 2004
    Long Island, NY
    Full Name:
    Steve G
    Same here - Tubi tips on my 430. Great sound all the time....
  6. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    #5 tazandjan, Jun 5, 2009
    Last edited by a moderator: Sep 7, 2017
    Darren- Do a search on "exhaust bypass valves" and you will get enough data to answer all your questions. There are differences in the way early bypass valves (ie 355, 550, 360) and later bypass valves (575M, f430, 599) are scheduled. In general, in the late cars the valves are open at idle, and close up to a certain throttle opening and rpm (~3000 rpm plus or minus 300 rpm). On earlier cars, the valves are closed at idle and open at wide open or some heavy throttle setting and ~3000-4000 rpm. Here is how it works for the 360.

    Terry Phillips
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  8. Steve R

    Steve R F1 Rookie

    Sep 15, 2004
    MeSoNeedy, CA
    Full Name:
    TorQ Master
    via a solenoid valve

    The solenoids open/close electronically and are controlled by the computer. Once they open, it just depends how much vacuum you have in the intake manifold (which is why, in neutral, you have a hard time opening them up). I've been able to go light on the throttle and get the rpm's way up past 5,500 and still not pop the valves. It's simple, yet complicated, enjoy playing with it and let us know what you come up with.
  9. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
    Melbourne Australia
    Full Name:
    Darren Liu
    Thanks Taz and Steve for your detailed reply.

    It seems like the 360 and 430's bypass valves are also operated via a solenoid valve just like the 355 (my car). This means that the bypass valve(s) operate once the rpm thresholds are exceeded and full throttle is detected.

    Not long ago, my mechanic plumbed the vacuum line straight off the engine to the oem bypass valve (my mistake). When idling, the bypass valve opened because it was receiving vacuum directly from the engine. When the engine was in nrevved in neutral, the bypass valve would close! Remember, the oem 355 bypass valve defaults closed and requires vaccum to open. I remember watching the diaphram steam move as the car was revved, there was instant response. Pity it was doing the opposite to what i wanted!

    Now, i have replaced the oem bypass valve with a 355 capristo one. This valve works opposite to the oem one in that it requires vacuum to close and springs open when vacuum drops off. The capristo diaphram failed last week, so i have to send it back for replacement.

    I was thinking, why not plumb the vacuum line from the engine directly to the capristo valve - The bypass valve would open instantly when the throttle is pressed (vacuum drops off under throttle, and returns when the throttle is released). Not sure what would happen at part throttle, say cruising in 6th gear at 3000 rpm.

    I'm keen to try this, as i believe the operation of the bypass valve via the solenoid valve/ecu is too slow.

    Any thoughts?
  10. eyboro

    eyboro Formula Junior
    Silver Subscribed

    May 30, 2004
    Full Name:
    Will a 360 bypass valve work on a 355?
  11. FerrariDublin

    FerrariDublin F1 Rookie

    Jun 14, 2009
    Dublin, Ireland
    Full Name:
    I think this should work as you describe - i.e. that the valves would open as soon as you apply even mild throttle. The only problem is see is that regardless of RPM, once you back off at all the valves will shut off immediately. This may or may not produce pleasing results! I'd say go ahead and try it out - I don't see it doing any harm.
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  13. SfefVan

    SfefVan Guest

    Nov 28, 2008
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  14. Ingpr

    Ingpr F1 Rookie

    Jun 30, 2009
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  15. FerrariDublin

    FerrariDublin F1 Rookie

    Jun 14, 2009
    Dublin, Ireland
    Full Name:
    To be fair, the OP isn't talking about disabling it or leaving it open permanently but I note the concern and if I were the OP I'd be doing some more research!

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