Nitpicked and Possibly NASA ST compliant s197 mustang engine cutoff circuit

Discussion in 'How To Forum' started by captdistraction, Sep 26, 2017.

  1. captdistraction

    captdistraction Not necessarily the Stig

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    OBLIGATORY DISCLAIMER: DO AT YOUR OWN RISK. I CANNOT BE HELD LIABLE FOR ANY LOSS OF LIFE, INCOME, RELATIONSHIP ISSUES, RUNNY NOSES OR LOSS OF PERCEIVED VALUE OF OPINION.

    Parts list:

    Cole Hersee 24106 12V Grounded Continuous Duty SPST Solenoid (amazon: https://www.amazon.com/gp/product/B001FQL43U/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)

    ~16” prefabricated (or make your own) 4GA red power cable with 5/16” or 3/8” ring terminals

    ~10’ of 14-18ga hookup wire, ring terminals, inline fuse holder, grommets

    1 SPST switch of your choosing

    Option: 1 generic battery isolator switch (I bought this $8 one: https://www.amazon.com/Qiorange-Bat...845&sr=1-8&keywords=battery+disconnect+switch)

    Option: rivnut tool to mount the solenoid, m6 bolts



    Install:

    Choose a mounting location for the solenoid. I had chosen the front of the passenger strut tower for proximity to the battery and the circuit I would be cutting off (the power feed to the smart junction box / fuse panel in engine bay). Drill holes and install riv nuts or bolts/lock washers/nuts/Loctite.


    [​IMG]



    On the battery, disconnect the negative cable and the power cable that routes to the fuse box. Install that cable on one end of the solenoid you just mounted. On the other main pole of the solenoid, install the 4GA power cable from the parts list and route/secure it and connect to the battery terminal so the circuit is so:

    Battery positive terminal -> solenoid -> smart junction box

    [​IMG]



    Then find a suitable location for your switch(es). My car is setup with one switch on a radio delete panel, and another on the cowl panel where the windshield wipers are. There’s a good location (pictured) where the wiring won’t interfere with the operation of the wipers (if used).

    Interior switch on console (with flipdown safety cover)
    [​IMG]
    [​IMG]

    cowl switch: (note, I had to move it slightly down from this picture to properly clear the hood, TEST FIT it before drilling)
    [​IMG]


    This circuit will look like this:

    Battery positive terminal (use the small stud) -> 18ga wire (short) -> inline fuse holder (with 5a fuse) -> interior switch location -> exterior switch location (in series) -> solenoid



    The solenoid body serves as its ground, so no need to run a separate ground wire unless you’re seeing issues with your mounted location or need to mount it to something other than the chassis.

    Finally, cover any exposed wiring with boots and/or tape

    By cutting off the SJB while running, the car won’t have power to its fuel system and ECU and this will effectively kill the motor. It’s not a true battery disconnect, however, that’s not what is required in the current rule sets for NASA.

    Diagram:

    [​IMG]


    Finished Product:
    [​IMG]
    [​IMG]


    Caveats:

    -Disconnecting the ECU can cause loss of learned parameters and stored diag codes

    -if the fuse in the switched circuit fails, the power will fail across the board (by design, obviously)

    I'll be adding pictures, having issues with previous hosting. Will edit soon.
     
    Last edited: Sep 28, 2017
  2. antman450

    antman450 TMO Race

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    You are the man! I send you a PM can you write a whole how to thread!


    Sent from my iPhone using Tapatalk
     
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  3. captdistraction

    captdistraction Not necessarily the Stig

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    updated with pictures and diagram
     
  4. Grant 302

    Grant 302 OPM Spent: $509,979 Moderator

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    I think your S2 and S3 in the diagram need to be wired in parallel, not series in order to activate the solenoid. Otherwise, both cowl and interior switch need to be activated. The way you have it the interior would be an 'arming' switch. I don't think that's the intent, right?
     
  5. antman450

    antman450 TMO Race

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    BTW, why don't you just use the upload a file option on the post?
     
  6. antman450

    antman450 TMO Race

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    If you wire in parallel, they you have to switch both off to turn off the solenoid. You cannot use just one switch. I imagine, the cowl one always stays on and is there for safety personnel, and the interior one is for you to use.
     
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  7. captdistraction

    captdistraction Not necessarily the Stig

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    That's absolutely the intent. If in parallel, neither switch would kill the car. Both switches need to be in an on state to start the car and that's by design. If you crash and are incapacitated for whatever reason, this gives an exterior switch that's easy to see and reach for corner workers to find (versus reaching over you into the car). Some sanctioning bodies require a switch to be easily accessible from the outside, so this both adds some safety and future-proofing for rulesets. My firesystem actuator pulls are in the same spots (one in the car, one on the cowl).

    otherwise, you can use the interior switch for convenience. I use both depending on what I'm working on.

    Most of this design might be considered overkill, but its all based upon my experiences which include cars on fire and crashes with the driver being disabled. Can never be too safe.
     
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  8. Grant 302

    Grant 302 OPM Spent: $509,979 Moderator

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    I don't think you guys are understanding me.
    If wired as shown, when you close one of those switches, *nothing* will happen because the other one is open. The solenoid in the relay will not energize and open the battery positive. You would need to close both to kill the battery connection. I don't think that's the intent.

    What I would do is put an arm switch in series with two kill switches in parallel. And LED 'armed' indicators near both kill switches.
     
  9. captdistraction

    captdistraction Not necessarily the Stig

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    This is the setup I've been running.

    You're right in that if one switch is open, nothing will happen (I'm not sure I used the right label for the switches but assume both are in a closed state to work, but they're both single pole single throw). Both have to be set to the on position for the car to be on, turning either off shuts off the car. The idea is that both switches need to be in an on state to energize the relay and provide power to the SJB.

    Keep in mind closing the switch turns the car ON, not off. The act of turning the switch off (and interrupting the circuit that keeps the solenoid energized) is what disconnects the power. I think what you're describing would be a situation where closing the switches would engage a disconnect

    This was the simplest way I could think of to build a circuit that required two switches to be on and would interrupt the motor if either switch was off. Also meeting my requirement that the alternator could drain to battery during power down and not toast itself on disconnect.
     
  10. Grant 302

    Grant 302 OPM Spent: $509,979 Moderator

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    That's the way your diagram is drawn!

    You're showing a normally closed relay when it sounds like you're using a normally open relay and the two kill switches to close the circuit. IF you drew S1 and S2 closed with the relay closed, or all of them open, that would make sense.

    So the car is stored with the battery disconnected and the memory cleared?
     
  11. captdistraction

    captdistraction Not necessarily the Stig

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    Should be normally open. I couldn't find a symbol to match it in the diagram, so I picked the closest.

    Correct, I store the car with the solenoid off and memory cleared, battery hooked up to a tender. One could build a bypass to maintain power to the ECU, however I've found more utility in the reset "side effect" than to build a bypass for my specific usage (dedicated racecar with no plate)
     
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  12. captdistraction

    captdistraction Not necessarily the Stig

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    I'll ms paint the diagram shortly to reflect the open default state
     
  13. captdistraction

    captdistraction Not necessarily the Stig

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    updated, hopefully clarifies and passes peer review
     
  14. Grant 302

    Grant 302 OPM Spent: $509,979 Moderator

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    Er... draw the 'arrow' pointing down/open and you're golden. Now it looks like a broken relay. ;) :eek:

    EDIT:
    Or add an "N.O." note near the relay contact. It's fine as is.
     
    Last edited: Sep 27, 2017
  15. WinterSucks

    WinterSucks TMO Addict

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    From the datasheet, it looks like the 24213-01 relay might be a better choice given the location. If they bothered to make a more vibration resistant and water resistant version then it might be safe to assume that the one you installed might fail at some point. Hard to say, but it is a weekend ruining failure. A spare would be a good idea. Is the fusible link upstream of the battery over 85A? If it is, a crash that damages the cable and grounds it could cause the relay to weld, but still not be enough current to overload the fusible link. If the voltage in the battery is still high enough even with the short then the pump/ECU might continue running. An upstream 80A TD fuse or the beefier 200A relay could be a fix for that.
     
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  16. Swiss Boss

    Swiss Boss TMO Addict

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    S2 and S3 switch are wired correctly. Because if something happen, corner worker can't reach the inside switch but they still can use the cowl one in order to shut down the car.

    My question is which box are you switching off?

    According to the Ford schematic, the box inside the engine bay is called "battery jonction box" and the one inside the car by the passenger foot well is called "smart junction box".
    If you're cutting power to the one inside the engine bay (which provide power to the smart junction box via a 80A fuse) you'll need a bigger solenoid than the one you linked above or you going to fry it.

    If you cut the link between the battery junction box and the smart junction box, you're fine with that solenoid.

    http://iihs.net/fsm/?d=711&f=013 - Power Distribution-SJB.pdf
     
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  17. captdistraction

    captdistraction Not necessarily the Stig

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    Power distro box mislabeled as smart junction box.

    Probably best to have mods delete this post until a better design is available. Mine has worked well however I don’t have all the circuits/load a street car has.


    Sent from my iPhone using Tapatalk Pro
     
  18. Swiss Boss

    Swiss Boss TMO Addict

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  19. Swiss Boss

    Swiss Boss TMO Addict

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    Your design is correct, you just need a bigger solenoid.

    A quick way to figure it out is to addition all the fuse that you're using in the battery junction box
     
  20. Grant 302

    Grant 302 OPM Spent: $509,979 Moderator

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    Understood. The drawing used to show a NC relay connection. I read that as needing power to the solenoid to cut power to the box. That's obviously not the case now.

    o_O
     

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