Ignition kill switch

[LTDScott]

I need to install an externally mounted ignition kill switch on my 24 Hours of LeMons race car. This is not for theft prevention, but for safety crews to shut off power to the car in the event of an accident, which means it needs to cut off alternator power too.

Has anyone done this before, and if so, how did you do it? Wiring the battery to the switch is simple, but I'm not sure about the best way to kill the alternator. I'm betting Spec E30 guys have to do this, so hopefully someone has some insight.

I'd likely mount the switch on the passenger side of the cowl (maybe use the RHD wiper hole) since it's very easy to access the battery junction on the firewall.

[Farbin Kaiber]

Use the summit style push/pull kill switch. It has a large gauge provision for a battery kill, along with a smaller set for the alternator or fuel pump.

[LTDScott]

Looks like I found my answer: http://spece30.com/component/option,...limitstart,10/

[ddavidv]

They can be a little funky to do. Let me know if you need clarity on any of it. I mounted mine in the hole in the cowl after you remove the right side cowl grille. Clearance is a bit tight but the 'standard' switch fill fit.

[rsafier]

Yep we mounted ours in the same place. We didn't completely do it to spec, but it works none the less. Nothing works when its off, and if the car is running and you hit it it shuts off all the relays & power to the computer so the car will die and the alternator will stop.
We kept the battery and starter hooked together. We pretty much just made it shut off all the fusebox power all the wires other then the big clamp stuff at the front positive juntion. It achieves the same basic prinicple, and didn't require us having to make even longer wires that we didn't have. It passed lemons tech without an issue this weekend (of course it was only highly recommended for Toledo, its required for Hoston and beyond).

Good luck BTW, we at Team 2 Slow racing : Flying Brick had a blast even if it was in 2nd gear for 22 hours straight

[LTDScott]

Did you guys do it the same way as this diagram, or differently?



Reading that SpecE30 thread shows me that there are several ways to do it, but the diagram above appears to be by far the easiest. The only catch is that I'd need a 6-post switch rather than the normal 2-post to separate the alternator and power supply circuits.

Rsafier, did they actually check the switch at LeMons tech to make sure it shuts off the car? If not, I could go a bit cheaper (hey it is a LeMons car) and get a 4-post switch and just not hook up a shunt (the resistor to ground). The downside to that is possibly killing the alternator.

We're hoping to get the transmission back into our car this weekend so it'll run again. Our clutch completely disintegrated in the last race, and we also had to replace the flywheel because we somehow lost the reference pin on the flywheel for the ignition timing. Porcubimmer shall rise again!

[ddavidv]

Yep, that's the diagram I used. Since I'm doing 'real' racing (ducks), I sprung for the better switch. The two prong design really isn't the right tool for the job.

[rsafier]

They did check it turned off power, I honestly can't recall if they tested to see if it shut engine off while running (it does the way we wired it). It was pretty chaotic with the rain and everything else, they were running very late with tech. I don't think we got thru tech until 12:30pm. There were like 3 teams at least that had to actually start welding in extra stuff to their rollcages because they didn't build them properly.

We at Team 2 Slow Racing loved the Porcubimmer, definately made us try to step up our game a little on the theme (shitty as it might still be). We have to completely rebuild our tranny as its stuck in 2nd gear (was for 22 hours of the race). We plan on just drilling and tapping the reference pin for a 10.9 bolt. I was too lazy to do it last event, but it seemed to hold in for 5K+ rpm most of the race. Still not gonna chance it next time.

The rules read "All cars must have a racing-type master electrical kill switch.". They are pretty cheap at Summit Racing, we got this one http://store.summitracing.com/partde...5&autoview=sku
Pretty happy with it.
Good luck with the next race. Perhaps next time you guys can make the trip to the Toledo/Detriot area, the only true 24 hours lemons race :)

[LTDScott]

Yep, that's the diagram I used. Since I'm doing 'real' racing (ducks), I sprung for the better switch. The two prong design really isn't the right tool for the job.

So the only cutting/splicing/changing of wires you had to do was at the firewall junction box, right? No modifications at the rear near the battery, or extra relays needed? This is what I'm hoping for. I realize that at minimum a 4-post switch would be needed because the alternator and the fuse box power circuits need to be separated, otherwise it won't shut off the engine.

They did check it turned off power, I honestly can't recall if they tested to see if it shut engine off while running (it does the way we wired it).

We at Team 2 Slow Racing loved the Porcubimmer, definately made us try to step up our game a little on the theme (shitty as it might still be). We have to completely rebuild our tranny as its stuck in 2nd gear (was for 22 hours of the race). We plan on just drilling and tapping the reference pin for a 10.9 bolt. I was too lazy to do it last event, but it seemed to hold in for 5K+ rpm most of the race. Still not gonna chance it next time.

The rules read "All cars must have a racing-type master electrical kill switch.". They are pretty cheap at Summit Racing, we got this one http://store.summitracing.com/partde...5&autoview=sku
Pretty happy with it.
Good luck with the next race. Perhaps next time you guys can make the trip to the Toledo/Detriot area, the only true 24 hours lemons race :)

Thanks for the heads up. Now that we have a new clutch and flywheel, let's hope the transmission holds up!

As mentioned above, I'll need a 4-post switch. How did you wire it up with a normal 2-wire switch?

Thanks for the props on our team. Unfortunately our theme effort won't be as strong this time since we're stretched on funds and are more focused on getting the car running, but our car will still definitely stand out.

Yesterday we fired up the car for the first time in a few months, so we're pretty excited. We just need to finish up the transmission and driveshaft install and hopefully the car will be up and running again.

It's a 10 hour haul to Thunderhill, so any further would be a major pain in the ass!

[jlevie]

While a 6-pole switch and resistor is the preferred solution, in an E30 you can get away with a 4-pole switch. The simple method, documented on the Spec E30 site, works because the small wire from the battery powers the engine management system and the large wire powers everything else. With the ignition switch on, there's enough load from other things to usually prevent the alternator from spiking high enough at shut off tho damage anything. So is the switch is used only as an emergency kill, you can usually get away with leaving the resistor out. But If you are going to use the kill switch in place of the ignition switch you really should use a 6 pole switch and the resistor.

If you use the simple installation (interrupting each of the two cables from the battery on separate switch contacts), the drawing above is incorrect in the wiring of the resistor. When the switch is off the resistor needs to connect the main power lug to ground as that's where the alternator connects.

[LTDScott]

So is the switch is used only as an emergency kill, you can usually get away with leaving the resistor out. But If you are going to use the kill switch in place of the ignition switch you really should use a 6 pole switch and the resistor.

If you use the simple installation (interrupting each of the two cables from the battery on separate switch contacts), the drawing above is incorrect in the wiring of the resistor. When the switch is off the resistor needs to connect the main power lug to ground as that's where the alternator connects.

We only plan to use it as an emergency cutoff. The car still has the ignition switch and key (although I plan to add a starter button so I can restart the car easily in the event of a spinout, etc). Hopefully we never have to use the external switch.

The above diagram is straight from the SpecE30 board, and has been confirmed as working correctly, so I'm not sure about the resistor to ground. Having said that, I still think we'll use a 4-post switch, as it will be an emergency cutoff only (and will be labeled as such).

[jlevie]

I realize that the diagram is from the Spec E30 forum, but it is still wrong with respect to the resistor. A few minutes with the ETM will confirm my assertions.

As I said, the chances of damage to the electronics is pretty low with a 4-pole switch or with the resistor improperly connected as long as the kill switch is only used to prove its operation at tech or in an emergency.

[LTDScott]

As I said, the chances of damage to the electronics is pretty low with a 4-pole switch or with the resistor improperly connected as long as the kill switch is only used to prove its operation at tech or in an emergency.

I'm going with those odds. Thanks for the help!

[rsafier]

We simply had a patch cable run from the primary postive juntion in front to the switch, then all the auxiliary/fusebox wires to the other part of the switch, so all it was really shutting off was all the power to fusebox and injection electronics. Its not the right way but it works, as it will kill the engine due to EFI and fuel pump turning off.

Yeah we had one of the members talk to a guy at Metric Mechanic today about transmissions and rebuilds, strenght, etc. He said while fairly rare to have the failure mode we did (pretty sure shift fork/rod is broken and that is our issue). That if we put in later i-style tranny they are much improved even over just the couple of years. We have 2 laying around that are okay and just need drilled for the ETA sensors. Cause they won't sell us their better parts or anything they use, just offered a 'deal' at 2200 for a MM rebuild.

DIdn't you guys also have ECU issues? If you don't have any spares I can ship ya off ours that works great, we had to go thur a couple before we found good ones that wouldn't wig out after 2-3 hours of running. Stupid caps start dying on them (our EE member's hypothesis) but he never did get around to trying to refresh one by replacing them all.

[LTDScott]

We simply had a patch cable run from the primary postive juntion in front to the switch, then all the auxiliary/fusebox wires to the other part of the switch, so all it was really shutting off was all the power to fusebox and injection electronics. Its not the right way but it works, as it will kill the engine due to EFI and fuel pump turning off.

Yeah we had one of the members talk to a guy at Metric Mechanic today about transmissions and rebuilds, strenght, etc. He said while fairly rare to have the failure mode we did (pretty sure shift fork/rod is broken and that is our issue). That if we put in later i-style tranny they are much improved even over just the couple of years. We have 2 laying around that are okay and just need drilled for the ETA sensors. Cause they won't sell us their better parts or anything they use, just offered a 'deal' at 2200 for a MM rebuild.

DIdn't you guys also have ECU issues? If you don't have any spares I can ship ya off ours that works great, we had to go thur a couple before we found good ones that wouldn't wig out after 2-3 hours of running. Stupid caps start dying on them (our EE member's hypothesis) but he never did get around to trying to refresh one by replacing them all.

Thanks for the info. I think we'll try the method in the diagram first since it seems to be easiest and involves the least amount of (potentially unreliable) wiring.

Yeah, we had ECU issues. Car was running at half power, wouldn't rev above like 3K RPM. I was playing around with the car in the garage one day after the race and accidentally dropped the computer and the engine sprang back to life.

We already have a spare computer, but I may take you up on your offer for a couple more. The more the merrier! On that note, I really need to get more spare parts for the car. Unfortunately we can't really afford much for spares, so I'm hoping we might be able to get a parts car and strip it for parts. I'd love to have a parts car to tow up there, but we have enough problems getting the race car up to the race, let alone another car.