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Exhaust bypass valve operation

Discussion in '348/355' started by INTMD8, Aug 4, 2015.

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  1. eyboro

    eyboro Formula Junior
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    Eitan
    #26 eyboro, Aug 12, 2015
    I have an OEM bypass valve which I refurbished to better than factory specs, valve opens a at around 2500 - 2700'RPM as opposed to 3500 RPM and guaranteed to never rattle again, send me PM if you're interested,
     
  2. INTMD8

    INTMD8 F1 Veteran
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    #27 INTMD8, Aug 12, 2015
    How do you have it set to open earlier? (isn't vacuum to the valve controlled by the ecu?)
     
  3. f355spider

    f355spider F1 World Champ
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    #28 f355spider, Aug 13, 2015
    That is what I thought as well. But I think he is using a different spec diaphragm that takes less vacuum to actuate. So it reacts more quickly to vacuum changes.
     
  4. INTMD8

    INTMD8 F1 Veteran
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    #29 INTMD8, Aug 13, 2015
    Still don't see how that would matter. If the solenoid doesn't send vacuum to the valve until say 2800, how would it open earlier? There is zero vacuum at that point.
     
  5. gothspeed

    gothspeed F1 World Champ

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    #30 gothspeed, Aug 13, 2015
    As was mentioned above .... on a 5.2 355 there is no reason to wire the bypass valve open ..... there is no HP benefit and it will trigger sensor codes and eventually a CEL .... and as long as the ECU controls the bypass vacuum solenoid, the bypass will open when the ECU triggers the solenoid ..... there may be some delay but only if the vacuum circuit is weak/has a leak, there is a pinch on the vacuum hose or a similar restriction.
     
  6. junglistluder

    junglistluder F1 Rookie
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    #31 junglistluder, Aug 13, 2015
    But it won't idle as loud! :)
     
  7. INTMD8

    INTMD8 F1 Veteran
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    #32 INTMD8, Oct 12, 2015

    I finally got around to doing this today and I'm 100% happy with the results. The bypass works exactly how I want it to now. With moderate driving, instead of it instantly going quiet on the next gear change and waiting for motronic to command it open again, it stays open for minimum 2 seconds after any command open signal from the motronic.

    So, if you roll on the throttle in any gear and bypass opens, when you lift and grab the next gear the bypass is still open so you get a nice bark from the exhaust instead of it quieting back down. If you stop accelerating the valve closes in 2 seconds and is nice and quiet again.

    Just sounds much more natural to me instead of going loud/quiet/loud/quiet on each gear change.

    The following videos I made just so you can hear how it works. (I don't usually drive like that, but wanted to make sure the bypass operation could be heard).

    Basically all this takes is a delay off relay (I used one made by Hella). Unfortunately it only accepts a + trigger so I had to wire in a second relay between the motronic trigger and the time delay relay to convert from negative to positive trigger.

    https://www.youtube.com/watch?v=VdJ7CyZIWHE&feature=youtu.be

    https://www.youtube.com/watch?v=O2Cb7BGNsAo&feature=youtu.be
     
  8. nathandarby67

    nathandarby67 F1 Veteran
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    Feb 1, 2005
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    #33 nathandarby67, Oct 13, 2015
    Love the ingenuity here! Very cool idea. I have a Nouvalari super sport exhaust which also has a very big difference in the sound level when the bypass opens, so the loud/quiet/loud effect you noticed is also very pronounced in my car. I think I may try your solution to see how much I like the difference.

    Would you mind posting a link to the relays you used?
     
  9. INTMD8

    INTMD8 F1 Veteran
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    #34 INTMD8, Oct 13, 2015
    Thanks! The delay relay is Hella 996152131. The second one is just a standard automotive 12v relay I had laying around.

    I can post up how to wire it this afternoon.
     
  10. Orange Crush

    Orange Crush Karting

    Dec 30, 2009
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    #35 Orange Crush, Oct 13, 2015
    Newbie question,

    On a 95, does the bypass open over a certain rpm or with a certain amount of throttle pressure? Mine won't open until I'm 3/4 in the throttle no matter the rpm? Is that normal?
     
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