Ignition wiring and kill switches

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cantfindausername
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Ignition wiring and kill switches

Post by cantfindausername »

Hi all,

I've had an idea of something that I'd like to do to my car. Its not really of any true functional value, but its still something I'd like to undertake - if my thoughts are correct.

My idea is to remove the standard key'd ignition and steering lock from the car, and fit an FIA battery master swtich, ignition toggle switch and an engine start button.

I need to look a bit into power supply to the cars alarm system (no standard alarm/immob.) as this would remain on the car for immobilisation and remote central locking. Unless it really needs to come off or cannot be wired around.

Has anyone done something similar to this to their own car? Any tips or advice on the subject would be great.

Thanks,
Ant
hcd
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Re: Ignition wiring and kill switches

Post by hcd »

Hi Ant,

The master switch severs the battery negative terminal / chassis connection, so you won't be able to use the battery at all. You could either run a second battery / split charge system or connect the 'always on' components directly to the battery negative.

You may as well install a fuel pump switch also. Useful when diagnosing start up problems.

Huw
cantfindausername
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Re: Ignition wiring and kill switches

Post by cantfindausername »

Hi Huw, thanks for the reply. I had also planned to wire the fuel pumps to switches. One for the stock pump feeding the swirl pot and one for the main pump. If thats how the system is going to be configured, just forgot to mention it.

I wasn't aware that it was the battery/chassis earth connection that was severed so thanks for advising me on that. Will hopefully enable me to plan out my wiring a little better now that I know that.

I think I will wire the components direct rather than messing with a split charge/twin battery system.

Ant
cantfindausername
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Re: Ignition wiring and kill switches

Post by cantfindausername »

Ok, been thinking about this and trying to get a list of components that would need their earths directly wired to the battery.

My list so far consists of:
Stereo.
Alarm.
Central Locking.
Interior light.

One question I've come up with is wether or not ECUs need a constant supply of power. I'm currently having a pectel SQ6 ecu fitted to it, and wondered how ECUs react to having the power supply cut.

My only expereince of ECUs is the stock one on the car. It has the abbility to "learn" how the driver drives and adjust itself accordingly. One common trick with these is to "RESET" the ECU to wipe the learnt mapping and revert back to the base map and slightly improved performance due to it giving you all you want rather than what you might do according to how you have been driving.

So my question really is; Are standalone ECUs safe to remove from the power supply? Or would it need to be constantly wired?

Thanks,
Ant
Georges Fonso
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Re: Ignition wiring and kill switches

Post by Georges Fonso »

Hi ant!
Standalone ECUs are, as a matter of fact, racing ECUs intended to be used on vehicles obligatorily equipped with a master switch/ battery isolator. I reckon you wouldn't have any sort of problems. Plus, as far as I know, most high-end ECUs store any "self-learning data" in non-volatile memories. Just about like the new generation of OEM ECUs do nowadays...
Regards,
G.F.
cantfindausername
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Re: Ignition wiring and kill switches

Post by cantfindausername »

Hi Georges, Thanks for the reply. What you've said has pretty much cleared up what my thoughts were.

Thanks again,
Ant
miro-1980
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Re: Ignition wiring and kill switches

Post by miro-1980 »

Interesting discussion,

I have a question or two on the subject.

My battery is in the back of the car. So connecting a kill switch mens I have to run a large diameter cable from the negative terminal to the switch on the dash board and ground it somewhere near the switch. Any possible ill effect of the ground cable beng this long?

I also take it that if I wanted the energency lights or a radio to work at al times I need to ground it directly from the kill swith (multi prong kind).

Do I have this right ?


Miro
craigb
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Re: Ignition wiring and kill switches

Post by craigb »

Run the earth from your battery box in the boot to the chassis on a short cable , it needsto be above 120 amp rating (i think mine is nearer 200 ) then take a long power cable to the cut off on the dash board .

this gives you 12 at the dashboard from which you can wire the essential circuits alarms etc , and just having the cut off killing the ignition and fuel pump.

earlier in the thread , someone said that the cut off has to be on the earth side , this is not the case , and not how the installation diagram in my Autolec FIA switch shows it being done


http://img.photobucket.com/albums/v714/cbgb/C026.jpg


http://img.photobucket.com/albums/v714/ ... switch.jpg
Book No 488
Guy Croft
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Re: Ignition wiring and kill switches

Post by Guy Croft »

Make sure you use a kill switch with alternator protection, if you don't and the battery gets isolated when the engine is running it will burn out the alternator diodes.

GC
Rich Ellingham
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Re: Ignition wiring and kill switches

Post by Rich Ellingham »

Craig is right. Use an autolec FIA master, it has a ballast resistor to power down the alternator output, and a seperate break to kill the power to the coil to prevent the alternator keeping the engine running on. I run from the battery to the master switch, its the only thing on the positive side of the switch. Then from the switched side I a main power feed to a 40 amp relay, and another feed to an ETA thermal breaker, which in turn goes to an ignition switch, this small power feed also powers things not required being controlled by the ignition switch (cannot think of anything in my case except the lights). When the igntion swich is on the main relay is activated and power flows to the rest of the fuse board. The ground of the main power relay goes via the ecu, so it has the ability to kill all things like fule pump and coil if the engine stops (like spinning the car while still in gear).

Rich
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cantfindausername
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Re: Ignition wiring and kill switches

Post by cantfindausername »

Rich, can you tell me what a Thermal Breaker is and whats its used for please? Thanks

This sounds very similar to the set up I'll be trying to accomplish on my car when I get it back.

Thanks,
Ant
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