V1 Kill Switch "Kill" Circuit

[duthehustle93]

Hi All,

I'm wiring in a Longacre 52-45782 4 pole kill switch and I was curious what circuit you interrupted on the "kill" poles? My goal is a battery isolator + kill @ >3000 RPM.

2 poles will obviously interrupt the battery, but for the other two, what circuit did you interrupt to kill the car without frying things? I'm about the finish up the wiring harness, so now is a great time for me to tap into an interrupt circuit.

If anyone is curious how #05 is going.... very slowly lol. Sitting for so long has really taken a toll on it: I finished rebuilding the engine early this year (it was seized from rust), lots of missing parts, weird unknowns, and some rat damage on the wiring harness. But mostly it's just me taking forever.

Thank you!

 

[Ross]

If you are cutting the power at the battery with this switch, that will kill the engine too, as the computers will shut off.
Maybe a wire from the ignition would be a good source to interrupt... as if the key requested the engine to be off.

 

[Desert Sasqwatch]

If this is a kill switch for racing requirements, the battery power to the engine and other electrical equipment is required to be cut off. But, as @Ross mentioned, the ECU power shouldn't be cut - so a small gauge wire that is not switched should be run from the hot battery lead (through a fuse and diode) to the ECU 12V input. The racing officials will test the switch to cut off the engine (and fans, etc.), but will not check to see if the ECU has power or not. This is just my recommendation, others may have ideas too how to wire this kill switch into the harness.

 

[duthehustle93]

Thanks Ross, I was not aware that killing battery would kill the engine for this chassis. On cars that I'm used to, interrupting battery would not shut off the car as the alternator would keep it alive. Hence the need for 4/6 pole kill switches, so I just assumed this would be the same case.

@Desert Sasqwatch, what is the reason that these ECU's need constant power? I was debating interrupting ECU power for kill which I've done on other cars, albeit 90's era stuff.

 

[ah.b.normal]

Thanks Ross, I was not aware that killing battery would kill the engine for this chassis. On cars that I'm used to, interrupting battery would not shut off the car as the alternator would keep it alive. Hence the need for 4/6 pole kill switches, so I just assumed this would be the same case.

@Desert Sasqwatch, what is the reason that these ECU's need constant power? I was debating interrupting ECU power for kill which I've done on other cars, albeit 90's era stuff.

I am also curious on this point, killing that fused feed off the battery to the BCM, to me, seems to be the same as removing the positive post during a battery change?(though I will be the first to admit 'puters can be delicate and sensitive creatures.)
I think I would prefer to kill power to the ignition circuit and the Alt. 10* wire from the starter + pole to the alt.(to be sure) I sure ain't no Lectrician! These answers can only help me later.

 

[Ross]

Thanks Ross, I was not aware that killing battery would kill the engine for this chassis. On cars that I'm used to, interrupting battery would not shut off the car as the alternator would keep it alive. Hence the need for 4/6 pole kill switches, so I just assumed this would be the same case.

@Desert Sasqwatch, what is the reason that these ECU's need constant power? I was debating interrupting ECU power for kill which I've done on other cars, albeit 90's era stuff.

You are probably right... the alternator will keep the car alive if you cut the battery when it is running.

 

[duthehustle93]

I just realized that theres a huge thing I'm not taking advantage of... none of this wiring is "done", so I can change the harness to make sense for a kill switch.

Please correct me if I'm wrong, I'm trying to "guess" how power distribution works on a Goblin...

This is how power distribution "normally" works for a Goblin, right?

Here's what I'm thinking. I'm going to mount the kill switch somewhere near the steering wheel. I'll make 2 separate runs of 4awg wire, with the first being pre-kill-switch and between the battery and alternator. The second run will be post-kill switch and feed the starter, fuse box, and BCM. When the switch is closed, everything is the same as the factory distribution, but when it's opened it will kill power the BCM/fuse box, killing/depowering the car, but still allow the alternator to feed into the battery for the 1-2 seconds that the engine is slowing down. I realized that I don't think I actually needed a 4 pole switch. Please let me know if anyone sees any issues with this. At the moment, I have an unwired/not even close to running Goblin, with no Cobalt experience to lean on... so I could be overlooking something here, and I don't want to fry anything.

Also while I have everyones ear and I'm working on the wiring harness... I'm on video 10 of 11 where you solder the EPS connector to an open wire on the main harness, and I did not have any open wires. The PO started the wiring harness on this car, and this post helped me trace down the potential issue... basically they wired the EPS output at the fuse box to the BCM 'D1' (the yellow line).. which I don't think is correct? The EPS wire was wired per the yellow line, but I rewired to the green/blue lines.
Are all of these assumptions correct?
1) The EPS output at the fuse box should run directly to the EPS connector (green line)
2) BCM X3 connector, pin D1 is power input to the BCM?
3) BCM X3 connector, pin D1 should pigtail into the red 50A fuse, and just be left as a tail (blue line), waiting for 12V battery power?

 

[duthehustle93]

I was realizing that in my schematic, theres a hot wire that would run the length of the goblin between the alternator and battery... so I'd need to fuse that. Or, alternatively I can use the Goblin wiring "as is" and use one pole to disconnect the battery, and the second pole to disconnect the alternator field wire.

 

[mike_sno]

I have a single pole kill switch on my battery negative pole. If you have some time I can try if the engine keeps running if I open the switch.