ian89C4

To the forum,

I just installed a cutoff switch and now thinking about it, something has me perplexed. Granted it is just a two pole, and I think I am already going to switch to a 6-pole I guess it is (even though I can't even try the 2 pole because the engine is out of the car).

But here is what gets me, I checked on some other threads, but I don't see the sheer amount of cr*p attached to theirs.

I have to cables going onto the positive pole of the battery. One thick braided copper wire as you would expect to find, and a cable that has three smaller wires within it. I also had two accessory wires comming from one of the wire bundles against the front bulkhead going to the terminal. I spliced them all and attached them to cutoff switch, to late now, but should I have done that??

Below are pics of the switch.

Also, has anyone put a 6-pole switch into an 89 C4? If you have can you walk me though it??

Many thanks right off the bat!!!

roblav

That wiring is insane. Simply run the cuttoff switch through ground. I wired my formula car that way.

A better method is to use a relay near the battery with a switch on the dash. That way, you can cut off the power without having to open/close the trunk.

ian89C4

Would just cutting-off the ground work with a 6 pole switch?

I understand that it would have the same effect, in that it would kill power to the car and would work for the 2 pole, but I am switching over to the 6-pole already (its on its way) and everything I have seen and read says to use the positive leads.

I do have a pull cable that comes out from under the hood. It works beautifully and I don't have to drill or remove the drivers side windshield fluid nozzle.

Thank you for the reply!!

Here are the instructions for the 6-pole switch I have coming.

http://www.pegasusautoracing.com/pdf...structions.pdf

roblav

Ian,

The simplest thing to do is to use a two pole cutoff to disconnect the main ground between the chassis and the negative terminal of the battery. It will work fine, but you cannot pull that cable while the alternator is turning or you might fry the alternator diodes. It all depends on what purpose you want for the cutoff. The emergency remote cutoff required for road racing is not required in autocross. If you simply want to prevent battery drain while the car is sitting, and you do not pull your cable until the engine has stopped, then this method will work fine.

The reason one would use a 6 pole cuttoff is to prevent killing the alternator diodes if you disconnect the current while the alternator is spinning. But again, it all depends on the intended purpose of the cutoff.

There's also an alternative wiring scheme for a two pole switch (which is cheaper), and this is how I wired up my formula car (with an alternator) and a remote 2 pole cutoff. Wire the cutoff between the battery negative and the chassis ground, then run two small (about 14 AWG) wires from the alternator positive terminal to the positive side of the battery and alternater ground terminal directly to the battery negative.

So your six pole switch will work fine though on the positive side... the only negative I see about your method is that you'll have to open the trunk to turn the switch back on. But that's not so difficult...

roblav

After thinking about this a little more, I would use an electrical relay as the battery cutoff switch. You can get an aircraft type from Aircraft Spruce for about $35.00. Then you can put a simple two pole toggle switch on the dash to control the relay. No cable... works to turn off AND on. But you could not flip the toggle switch off while the car is running unless you ran the two wires from the alternator terminals as I described.

ian89C4

I am slowly getting the car ready for PCA club racing. I only need the switch for the emergency disconnenct.
Thank you for all of the info, it does all make sense.

Do you know what the large cable with the three wires runs to??

garrett376

If you're PCA racing, a cut-off to the ground "won't cut it."

See this thread for proper 6-pole wiring:
https://rennlist.com/forums/964-foru...right-way.html

ian89C4

Garrett376,

Thanks for hopping on, I have looked at your post about a thousand times. Still have questions though. The DME part is straight forward. Did you have two large cables going to the positive terminal of your battery though? I only see one coming from the battery. This is my biggest thing. I have to splice all three wires and it takes up a lot of room on the connections. What is this other cable?????

Thank you!!

garrett376

I made a Y-junction where those two cables came together first, then only leaves the junction. I had to do this also because the POC rules for a cutoff switch require the switch to be behind the front shock towers; so instead of routing two long hot cables, I made them join together, with just 1 long one running from that junction. Does that makes sense? If not, I can see if I have some pics somewhere!

ian89C4

That makes perfect sense, now I just have to find a y-junction some where. Thank you for the info!!!!!

roblav

I read the post, and it sure seems like a lot of effort to meet a POC rule which makes no sense... for once, our SCCA rule is better.

garrett376

Their reasoning (likely most applicable to old 911's) is if the front end is smashed in, the switch can be damaged and rendered nonfunctional; therefore keeping it behind the shock towers helps increase the likelihood it will remain functional. Whether it's better is subjective and irrelevant. But on a 911, if you wire a 2-pole cut-off switch to the ground, the engine will not be stopped (which you recommend above). SCCA allows that configuration? Yikes

Anyhow... Ian, to make a Y-connector, I just bought some crimp on connectors from the auto-parts store, crimped on two connectors, bolted them together, which bolts to wire that then heads to the switch itself. Works great, and is easily reversible if needed.

garrett376

Hard to see it here, but the two big black wires on the floor of the trunk get new crimped on connectors, then they bolt to the long black wire that goes to the cut-off switch, which then returns to the battery.

roblav

Garret - my comment concerning the rule was not about the location of the cutoff but about not allowing to install the cutoff through the ground. With the ground cut, the engine will stop - no current flow.

garrett376

Just like vintage race cars with no battery, the alternator will provide enough current to keep the engine running. Rev that engine, pull the switch, and the engine will continue running - we do this all the time at post-race impound when someone shows up with a car with a 2-pole wired through negative ground. It'll even keep running off the positive, too, which is why a 2-pole switch is silly on a car with an alternator!! 6-pole is the only way to go to stop an engine right away, for good, regardless of RPM.