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  1. #1
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    Forcing Exhaust Flap to closed position

    Ok so we have the Jb4 CANflap feature to keep the flap open, but I'm looking to setup a solution to also be able to force it into the closed position. So basically a switch that can be used to switch from open to closed on demand.

    From what I can see so far 12V = flap open and ground (0V) = closed. So if I were to wire in a 12V on/off switch to the plug in the trunk I am assuming I could control the flap?

    I gave someone this idea for a custom exhaust setup last year and it worked perfectly for them, but they knew how to do the wiring themselves, I'm afraid of making a critical error when it comes to the electrical systems so any help/advice/how-to etc... would be appreciated.
    jb4+fbo+meth

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    Click here to enlarge Originally Posted by Dr. G Click here to enlarge
    Ok so we have the Jb4 CANflap feature to keep the flap open, but I'm looking to setup a solution to also be able to force it into the closed position. So basically a switch that can be used to switch from open to closed on demand.

    From what I can see so far 12V = flap open and ground (0V) = closed. So if I were to wire in a 12V on/off switch to the plug in the trunk I am assuming I could control the flap?

    I gave someone this idea for a custom exhaust setup last year and it worked perfectly for them, but they knew how to do the wiring themselves, I'm afraid of making a critical error when it comes to the electrical systems so any help/advice/how-to etc... would be appreciated.
    The "flap" is vacuum operated its not a 12v relay pushing the flap. I'd ask Terry for a added feature to the JB4, but this might not be considered a feature anyone else wants...
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    Click here to enlarge Originally Posted by Dr. G Click here to enlarge
    I gave someone this idea for a custom exhaust setup last year and it worked perfectly for them, but they knew how to do the wiring themselves, I'm afraid of making a critical error when it comes to the electrical systems so any help/advice/how-to etc... would be appreciated.
    Click here to enlarge Originally Posted by xbox_fan Click here to enlarge
    The "flap" is vacuum operated its not a 12v relay pushing the flap
    If this worked it would suggest it is not vacuum operated. The fact the JB4 can control the flap would support that theory.
    I don't know if a not connected exhaust solenoid (if it is electrically operated it probably would use one) would throw a cell.
    If it would, making a switch in the wire before the solenoid and using a 47 Ohm 5W resistor to Ground the wire would probably fool the system.
    If it does not throw a cell, using the switch as a braker of the wire would be enough.
    Sort of like a Whisper mode.

    Not sure why you want that for WOT though. It is restrictive.
    There are two theories to arguing with women. Neither one works

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    Click here to enlarge Originally Posted by xbox_fan Click here to enlarge
    The "flap" is vacuum operated its not a 12v relay pushing the flap. I'd ask Terry for a added feature to the JB4, but this might not be considered a feature anyone else wants...
    It is a vaccum operated solenoid, but there's an electrical signal controlling the vaccum pump is there not? I have used a green (I think green) wire in the ECU which is an RPM feed to open and close another valve so I am guessing this same signal is relayed to the actuator somehow when it opens and closes based on RPM.

    And I think this feature could be useful when getting a bit creative.
    jb4+fbo+meth

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    The vacuum source comes from the vacuum pump, same one that operates the waste gates. The flap is controlled by a solenoid valve that applies vacuum to the actuator when the valve is energized. From what I can tell, the flap is only closed on cold start ups when the RPMs are high to limit the exhaust noise.

    You could make use of this vacuum source and control solenoid to do somethings like operate a cut out once a certain RPM was reached to keep the car from being unnecessarily noisy around town, but allow it to breathe freely when opened up.

    I would recommend removing the connector from the solenoid and installing a fixed resistor with a resistance equal to the resistance of the solenoid. This way the DME would not be able to tell the solenoid was not connected, preventing the MIL from lighting up. You could then just apply battery voltage across the solenoids terminals to open the valve.

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    Click here to enlarge Originally Posted by Dr. G Click here to enlarge
    So basically a switch that can be used to switch from open to closed on demand.

    Why doesn't it work like this by default?

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    Click here to enlarge Originally Posted by xbox_fan Click here to enlarge
    The "flap" is vacuum operated its not a 12v relay pushing the flap.
    Well that explains that.

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    Click here to enlarge Originally Posted by Dr. G Click here to enlarge
    It is a vaccum operated solenoid, but there's an electrical signal controlling the vaccum pump is there not? I have used a green (I think green) wire in the ECU which is an RPM feed to open and close another valve so I am guessing this same signal is relayed to the actuator somehow when it opens and closes based on RPM.

    And I think this feature could be useful when getting a bit creative.
    Lets get some clarification.

    @Terry@BMS

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    Click here to enlarge Originally Posted by xbox_fan Click here to enlarge
    The "flap" is vacuum operated its not a 12v relay pushing the flap. I'd ask Terry for a added feature to the JB4, but this might not be considered a feature anyone else wants...
    You can easily wire a switch in to open and close the flap when ever you want. This is what I did, it works perfectly.

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    Click here to enlarge Originally Posted by Dr. G Click here to enlarge
    It is a vaccum operated solenoid, but there's an electrical signal controlling the vaccum pump is there not? I have used a green (I think green) wire in the ECU which is an RPM feed to open and close another valve so I am guessing this same signal is relayed to the actuator somehow when it opens and closes based on RPM.

    And I think this feature could be useful when getting a bit creative.
    Yes, the actual solenoid is operated by 12v - It's found on the driver side in the trunk, behind the liner, relatively near the tail light. Ideally you want to wire it as a ground trigger.

    I put a micro switch in my ash tray, I have a custom exhaust that utilizes the flap.

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    Thanks for the helpful replies guys. repped!

    Click here to enlarge Originally Posted by ajm8127 Click here to enlarge
    You could make use of this vacuum source and control solenoid to do somethings like operate a cut out once a certain RPM was reached to keep the car from being unnecessarily noisy around town, but allow it to breathe freely when opened up.
    Read my mindClick here to enlarge. I am considering using an on-on-on switch where I could make the flap forced open, forced closed, or rpm controlled. This makes the car perfect for daily travel and for fun time.

    Click here to enlarge Originally Posted by fishmando Click here to enlarge
    Yes, the actual solenoid is operated by 12v - It's found on the driver side in the trunk, behind the liner, relatively near the tail light. Ideally you want to wire it as a ground trigger.

    I put a micro switch in my ash tray, I have a custom exhaust that utilizes the flap.
    Yup that's exactly where I was looking at, the thing is how would I know how to make sure everything is done safely? Should I be looking at the amps rating of the switch I will be running? I know what I want to do, but wiring/electrical is beyond the scope of my knowledge Click here to enlarge
    I cameup with the idea for my friend a long time ago, but he did the wiring part and I've lost touch with him since then so I'm a bit lost on that end.


    @Terry@BMS - Terry how about you make an exhaust flap closed position Click here to enlarge the big turbo guys who want a quiet/reasonable car, but still need high flow could benefit from this. You could use your OEM mufflers and just relocate the valve to a new position to run it as a cutout and pair it up with a second valve from somebody who changed their tips. Just a bit of welding labour and you have VACCUM controlled cutouts that won't giveup on you like electric crap-outs. RPM controllable as well Click here to enlarge
    jb4+fbo+meth

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    Click here to enlarge Originally Posted by Dr. G Click here to enlarge
    Yup that's exactly where I was looking at, the thing is how would I know how to make sure everything is done safely? Should I be looking at the amps rating of the switch I will be running?
    Measure the resistance of the solenoid, Divide 14.5 by this resistance and that is the steady state current. Use a fuse 50% bigger or so. Five amps should be plenty. 18 or 20 gauge wire is fine too.

    I would wire it from the battery through the fuse (don't run the wire very far without fusing it), then from the fuse to the switch, from the switch to the solenoid, then from the solenoid to ground.

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    Click here to enlarge Originally Posted by ajm8127 Click here to enlarge
    Measure the resistance of the solenoid, Divide 14.5 by this resistance and that is the steady state current. Use a fuse 50% bigger or so. Five amps should be plenty. 18 or 20 gauge wire is fine too.

    I would wire it from the battery through the fuse (don't run the wire very far without fusing it), then from the fuse to the switch, from the switch to the solenoid, then from the solenoid to ground.
    I did a 5A fuse and either 16 or 18GA wire IIRC. The switch I used was rated for 5-10A I believe, honestly it's an easy mod.

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    I think you might have emailed me on this asking for some info. As I said I'm swamped lately. But to point you in the right direction there is a signal that feeds in to the DME. Looks like its pin #11 on the gray subconnector, a gry/vio wire. I have not put a meter on it myself so not sure how the signal works exactly. But based on the wiring diagram it appears you ground that out to close the solenoid.
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    The OEM and PE exhausts uses flaps, does any other aftermarket exhaust do this or is it going to be a custom thing?
    Click here to enlarge
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    Click here to enlarge Originally Posted by ajm8127 Click here to enlarge
    From what I can tell, the flap is only closed on cold start ups when the RPMs are high to limit the exhaust noise.
    AFAIK, the flap is closed at low rpm to reduce noise during normal driving but opens around 4k.

    I've had my tune for years so mine is always open, but I believe that is correct.
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    The behavior of the flap my be different with different DME firmware revisions, but I know my flap is closed after startup, then once the idle comes down, the flap opens. It seems to stay open after that, even at idle.

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