Kill Switch

Sh0velMan

Any of you have an external kill switch wired up?

How did you wire it?

What hardware was needed?

Thanks!

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Sh0velMan

Wow, no one?

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GaleForce

We usually wait for the steering lock to fail.

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SouthArk370Z

I may be able to help, but, not being a drag racer, I have to ask: Exactly what do you need to kill? Ignition? Fuel pump? Battery disconnect?

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Sh0velMan

Everything.

Not for drag racing, not even required by any sanctioning body I'm associated with, I just want it as a safety measure.

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Kingbaby

I have one somewhere collecting dust! Like mention above the kill switch for everything is placed between the battery and the ignition I think. It's not a simple DIY.

The individual switches are easy like battery, fuel, clutch those are what I have done...

Mainly for anti-theft

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SouthArk370Z

The only effective way I know to kill everything is a battery disconnect.

For remote operation, you can use a fairly large single-pole relay and a conveniently mounted switch. Electrically, placing the relay next to the battery would work best, but I don't suggest placing anything that arcs in the battery compartment if you are using an unsealed battery (eg, OEM). You will need to get a relay with rated DC breaking amps greater than what the load is - I have no idea what full load is on a 370Z. To keep the size of the relay down, do not run starter power through the relay. You might want to also consider leaving the ECM powered up. Relay contact voltage rating should be at least 12VDC (or greater (I suggest >=25VDC) - higher is "better", but usually comes at the cost of increased physical size).


The easy way to kill just the engine is to kill the fuel pump - a small relay or manual switch should be easy to install.


I _think_ it would take a 6-pole relay to kill just the ignition (one pole per coil), but there may be a way to interrupt a signal to the ECM.

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Sh0velMan

A battery interrupt is the simplest, for sure.

I would love to be able to keep the ECU with at least standby power even when the kill switch is engaged, I just don't see how to accomplish that, unless we can figure out a way to power it through, for instance, the OBD II port.

I just hate to lose learned fuel data any time the car is killed.

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SouthArk370Z

I'll try to do some more investigating this afternoon, but just off the top of my head:

I've been looking through the FSMs lately and think I remember seeing that the ECM has multiple power supply terminals. Not sure if that would present a problem, electrically, or not. If they are all in parallel, it shouldn't matter. Like I say, I need to do some more investigating.

The CAN bus will only supply a limited amount of power and I don't think it's a good idea to tamper with the CAN bus if it's not absolutely necessary. Plus, you would have to bypass the battery disconnect to power the CAN bus.

It _should_ be fairly easy to maintain power to the ECM. If nothing else, you can install a small 12V battery just for the ECM. The biggest problem I can see would be if diodes were required to prevent the new battery from trying to power to whole car when the disconnect is de-energized. Diodes have a voltage drop that may mess with the ECM. More investigation needed.


Hopefully, someone that has done this before will chime in soon.

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SouthArk370Z

I _think_ I've figured it out. FSM EC-532 shows ECM terminal 93 (AKA Connector F102-93)* as being "Power Supply for ECM (Backup)" input with battery voltage applied at all times. Run a wire from the input of the disconnect relay contact(s) (or the battery terminal) to that terminal on the ECM and you shouldn't lose any stored data when you de-energize the disconnect relay.

*I'm not sure which of the three connectors going to the ECM is F102. Look for a pink wire in one corner of the connector. When you figure out which connector is which (F101, F102, and M107), please let me know.


References: 2009 FSM EC-148, EC-149, EC-523+, EC-536, EC-543


PS: You may want to de-energize the relay when you park for very long. It might run down the battery.

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SouthArk370Z

Does anyone know what effect a cold shutdown (disconnecting the battery) of the car has on the engine and other systems? It's safe to disconnect the battery when the car is off, but what about when you're tooling down the road at highway speed? A cold shutdown of an old (pre-computer control, no VVEL) car wouldn't worry me - all you'd lose is P/S and P/B - but I'm wondering what it would do to a modern car. Could you end up poking a hole in a piston with a valve? I'm not worried about radio presets or even ECM learned data, just things that would be harmful to the engine or other systems.

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takjak2

You can shut down the car while rolling (neutral may be required) by holding the start stop switch. No ill effects on a 6MT in neutral at ~45 mph and restarted while still rolling.

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Sh0velMan

I think SouthArk may be concerned that the shutdown process you describe actually IS a 'process' where the ECU powers down systems gracefully.

That said, I do not believe that cutting power will cause mechanical damage unless you are on the ragged edge of reliability, ie the split second after the fuel stops you get massive detonation from lean out. Not likely on a NA or even FI application since the throttles should snap shut at the same time.

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

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SouthArk370Z

Yes. That is exactly what I meant. I'm worried about an "ungraceful", yank-the-plug-out-of-the-wall, kind of shutdown. Thanks for clarifying for me.


Thanks for the input.

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Sh0velMan

This weekend I'll probably run the Z for a bit then yank the battery, see what happens...

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