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  • kill switch

    Just relocated my battery, NHRA rules require a kill switch.

    as in break the connection from the battery (easy), and kill the engine (disconnect a wire from the ICM).

    what wire should I run to a switch? all the way to the back of the car and back to the front. from what I have read the ground is the best way, but thats a long wire for a ground.. CPS? not sure if that will mess with the signal or not..
    sigpic
    88 Beretta CL- 13.641@102.76mph (rwd LS1/t56 conversion in progress)

    77 Celica GT- 3400/3500 swap in progress (engine from the beretta)

  • #2
    Use a relay?

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    • #3
      cutting the ICM won't necessarily shut down the engine.... if you run into preignition, you don't need a spark to keep the engine going as long as fuel is still being delivered. i'd run the kill switch for that as just a rocker or something to open/close the injector +12V feed. then as long as the injectors aren't leaking any significant amount of fuel, the engine will not produce power and shut down.

      breaking the battery circuit.... you're going to need a big switch.
      1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
      Latest nAst1 files here!
      Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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      • #4
        Another thing I've heard of is to interrupt not only the battery cable but also the alternator cable to completely shut off the power. I'm not really sure if the rules specify that the switch should only shut off the engine or shut off all electricity.
        '89 Firebird, 3500 Turbo, T56, 9-bolt/4.11
        '86 Fiero, 3500, 4-speed

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        • #5
          I would think all power to prevent a fire. I was going to do all power except a small feed line for radio memory.

          Sent from my HTC One X using Tapatalk 2
          -60v6's 2nd Jon M.
          91 Black Lumina Z34-5 speed
          92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
          94 Red Ford Ranger 2WD-5 speed
          Originally posted by Jay Leno
          Tires are cheap clutches...

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          • #6
            Do it the right way, Get a battery kill switch and interrupt the power, but remember now you need to also interrupt your alternator wire otherwise the car will keep itself alive.





            Battery is in the trunk so mount the switch in your bumper so its accessible from outside as the rules request.

            If you don't want the ECU to disconnect then run a wire that comes from your column for the IGN wire and go to a switch back there so it acts as if your shutting off the key but your not disconnecting power to the car... May not be exactly what they want but the ECU wont loose its learned parameters. Something I've been thinking about with mine.

            I'm unsure if their request for the switch is to be able to isolate a possibly shorting wire that is 10-15ft long going through the car OR simply be able to shut off the vehicle.
            Last edited by 3400-95-Modified; 09-26-2012, 12:41 PM.

            Got Lope?
            3500 Build, Comp XFI Cam 218/230 .050 dur .570/.568 lift 113LSA
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            • #7
              I always thought cutting fuel was a bad thing, just like starving it under hard accel. am I wrong?

              I like the idea of using the ignition switch. I think I will do that! I already have a taylor switch, it was cheaper than moroso

              one thing im not making sense of, the alt power wire already feeds into the main battery cable, wont that kill charging when the switch is off?
              Last edited by Alxsmt; 09-26-2012, 10:13 PM.
              sigpic
              88 Beretta CL- 13.641@102.76mph (rwd LS1/t56 conversion in progress)

              77 Celica GT- 3400/3500 swap in progress (engine from the beretta)

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              • #8
                Usually the alt cable goes to a power distribution block so if you only cut the positive cable power the engine will still have enough electricity from the alternator to keep running. You just wouldn't be able to start it again without turning the switch to on again.
                '89 Firebird, 3500 Turbo, T56, 9-bolt/4.11
                '86 Fiero, 3500, 4-speed

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                • #9
                  gotcha. your right. now that I think about it lol, seems like it goes to the starter along with a few other wires then to the battery.

                  so, if im reading the diagram right (good chance Im not), I just take the alt charge wire and move it directly to the switch? my switch is rated for 20amps like the moroso, my alt puts out maybe 100? makes me think im not understanding this stupid simple task lol. I was planning on using the 2 smaller posts to kill the engine
                  sigpic
                  88 Beretta CL- 13.641@102.76mph (rwd LS1/t56 conversion in progress)

                  77 Celica GT- 3400/3500 swap in progress (engine from the beretta)

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                  • #10
                    wait.. I get it I think.. killing the alt charge wire will kill the engine.. if I do the ign idea I wont need to worry about the alt wire.
                    sigpic
                    88 Beretta CL- 13.641@102.76mph (rwd LS1/t56 conversion in progress)

                    77 Celica GT- 3400/3500 swap in progress (engine from the beretta)

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                    • #11
                      Ok let me clarify this... The wire they want you to cut is the main battery wire that runs from the positive lead on the battery to the starter, On most cars including ours, the post on the starter is where the wiring harness gets most of its power including for everything inside the car, so if you kill that main wire going to the battery the engine will shut off, NOW the killer her is on a typical car the alternator is wired to the same starter post, so if you disconnect the battery the alternator will continue to supply power to the harness and keep the vehicle running. So in order to do it right the kill switch has to have two circuits on it, One is for the main power feed from the starter to the battery,(large posts In that install guide) the other is for the alternator to the battery(smaller posts in that install guide)... On the other side of that switch those two wires can connect back up together since they are both going to the battery but on the engine side of the switch they need to be isolated from each other so the alternator will not supply power to the engine when this switch is shut off.

                      Heavy load high RPM cutting fuel is a bad thing yes... but most cars will cut the fuel when your coasting down hill. Very often my wideband reads AIR when I'm coasting in my Subaru and the Beretta.

                      One issue I just noticed is those switches have a max of 20 amps for the alternator wiring... our alternators are rated at 100, but I'm not sure how much is typically drawn with what your doing. You may have to do this differently and run the battery wire through the switch as described and then substitute the alternator wire for the ignition circuit that comes from your key, but you would have to run that wire from the column all the way back to the switch have it go in on one side and come out the other and go back up front to where you split the wire, It would not connect to the battery as the alternator wire would. Wiring the switch this way would do two things, Kill the ignition circuit so essentially do the same thing as turning off your key, and at the same time it would kill the main battery feed wire so if they want this installed to protect against a short it will do that, as well as give them an easy way to turn off the engine if necessary. Wiring it this way you can keep the alternator wired as stock since you will be shutting off the ECU ign circuit as well as any other circuit that gets turned on when you turn they key on injectors, ICM, and so on.
                      Last edited by 3400-95-Modified; 09-27-2012, 09:08 AM.

                      Got Lope?
                      3500 Build, Comp XFI Cam 218/230 .050 dur .570/.568 lift 113LSA
                      Fully Balanced, Ported, 3 Angle Valve Job, 65mm TCE TB, S&S Headers.
                      Stage-1 Raybestos/Alto 4t60e-HD, EP LSD, 3.69FDR
                      12.61@105 Epping NH Oct 2015 Nitrous 100shot (melted plugs) 13.58@98.8 N/A 3200LBS

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                      • #12
                        WTF. The kill switch is outside the car and is for EMERGENCIES. Is not your normal on/off switch. Run the power cable and the fuel pump power (so it wont stay powered by the alternator) through the switch. You don't have to worry about someone flicking the switch while under full throttle. You wont run lean. You don't have to worry about the alternator because the fuel pressure is all gone and the engine will be dead.

                        If they will make you test the switch frequently then you can install dedicated power wires from the battery to the radio and ecm for memory saving.
                        1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
                        1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
                        Because... I am, CANADIAN

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                        • #13
                          thank you for clarifying that! I have a set plan now lol.

                          at the drags they test the switches, pretty sure it has to kill it right away. not sure if killing the fuel pump will do that because they test it at an idle, otherwise that would be the easiest way

                          thanks!!
                          sigpic
                          88 Beretta CL- 13.641@102.76mph (rwd LS1/t56 conversion in progress)

                          77 Celica GT- 3400/3500 swap in progress (engine from the beretta)

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                          • #14
                            i have a fuel pump kill switch in the MC.... it kills it pretty quickly, though it may not be the instant the inspectors want to see.
                            1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
                            Latest nAst1 files here!
                            Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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                            • #15
                              I don't think they are looking to kill the engine so much as they are stopping power to the car in the case of metal slicing into wire insulation and starting a fire. Yes, stopping the fuel source is a key but I don't think it's the main concern with the kill switch. When I think kill switch, o think total vehicle shutdown.

                              Sent from my HTC One X using Tapatalk 2
                              -60v6's 2nd Jon M.
                              91 Black Lumina Z34-5 speed
                              92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
                              94 Red Ford Ranger 2WD-5 speed
                              Originally posted by Jay Leno
                              Tires are cheap clutches...

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