Distance of wire between MSD and coil?

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STOICH
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Distance of wire between MSD and coil?

Post by STOICH » Mon Jan 12, 2015 9:30 pm

Does anybody know how far a MSD 6AL can be mounted from the coil? I want my MSD away from the radiator and fuel, etc. It would be about 13 feet in wire length total. Anybody know of any changes, wire size or whatever needed to do it?

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Re: Distance of wire between MSD and coil?

Post by Dale M. » Tue Jan 13, 2015 10:00 am

MSD in their specification states you can extend the length of the wire if you go next size (gauge) larger....

See MSD document: "Wiring Diagrams and Tech Notes" (WDTN) page 8.

http://www.msdignition.com/instructions ... terms=WDTN

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Re: Distance of wire between MSD and coil?

Post by STOICH » Tue Jan 13, 2015 11:27 am

Thank for the lead Dale. I was a bit unsure of the wording so I called MSD tech line as I wanted to clarify that the wires stated on page 8 could actually be the wires between the coil and the MSD box. I explained I'd like to mount the MSD in the front area of my rear engine car for the safety of the unit and my passengers. When the tech stopped laughing, he said "the standard length of wire provided is plenty long enough for your application. No. That is too long." The crystal ball this guy has is awesome.

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Re: Distance of wire between MSD and coil?

Post by jhoefer » Tue Jan 13, 2015 1:50 pm

14 gauge wire between the box and coil is capable of handling the coil's current (3-5 amps) over a 13 ft distance. No real need to increase wire gauge, but you can go to 12 gauge if you'd prefer.

If you are extending the mag pickup wires, make sure they are twisted together like the exiting wires to minimize interference. No need for larger than stock gauge wire here either as the current is very low.

Though I guess don't see the full reasoning of mounting it up front vs just sticking it in the engine bay.

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Re: Distance of wire between MSD and coil?

Post by Dale M. » Tue Jan 13, 2015 6:05 pm

Don't think I would put much faith in him as a tech rep...

I mounted the MSD box behind the seat of my buddies 32 Ford roaster and we had to extend the wires to coil and distributor, with no problem, fortunately battery was also behind the seat so main power leads were fine....

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Re: Distance of wire between MSD and coil?

Post by STOICH » Tue Jan 13, 2015 10:54 pm

jhoefer wrote:
Though I guess don't see the full reasoning of mounting it up front vs just sticking it in the engine bay.
Totally appreciate the feedback. I have alot of stuff crammed in to a pretty small area on my rail. Fuel injection stuff has sprung high pressure leaks before (atomized spray) and is not what I want near the MSD as I did catch the car on fire at one point from something similar. In another instance, I had a fuel tank leak severely in a roll over causing a huge puddle under the vehicle while upside down, so I don't want it near the fuel tank in the back of the car. If I can comfortably mount the MSD behind the dash I would be stoked. I guess I will just give it a shot and see how it goes. My only discomfort is I have a 100 mile drive to the desert to see if it actually works under normal driving conditions. I guess I will just be prepared to mount it in the back if it is acting weird. Thanks for the thoughts, we shall see

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Re: Distance of wire between MSD and coil?

Post by Marc » Wed Jan 14, 2015 12:33 am

Shouldn't be any limitations provided you follow the suggestions to go up a step on the wire gauge. As far as the coil-to-distributor high-tension lead goes, anything under ~3' should be no cause for concern. I've seen recommendations from MSD to keep it under 4-5"; the ol' "one-eyed-mechanic" rule in the days before high-energy systems was to keep the coil wire length below that of the longest cap-to-plug lead, if you stay under that you're essentially guaranteed to have no issues.

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Re: Distance of wire between MSD and coil?

Post by Piledriver » Wed Jan 14, 2015 6:03 am

If that is your concern you need a set of COPS and ditch the distributor entirely.

No exposed spark gaps.
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Re: Distance of wire between MSD and coil?

Post by STOICH » Thu Jan 15, 2015 1:26 am

Marc wrote: As far as the coil-to-distributor high-tension lead goes, anything under ~3' should be no cause for concern. I've seen recommendations from MSD to keep it under 4-5"; t
Maybe that is the confusion here. I am referring to the primary side, the 14 gauge wiring that controls the coil signal. The secondary wiring, or "coil-to-distributor high-tension lead" is only 6 inches long. Won't know until I try. I'll know by Monday :P

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Re: Distance of wire between MSD and coil?

Post by STOICH » Sat Jan 17, 2015 3:33 am

13 foot of wire from the squirt to the MSD... 15 feet from the MSD to the coil. Seems like it wants to give it a go.

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Re: Distance of wire between MSD and coil?

Post by Piledriver » Sat Jan 17, 2015 6:52 pm

Shouldn't matter for the primary side, doesn't the MSD just use logic signal for input?
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Re: Distance of wire between MSD and coil?

Post by Steve Arndt » Sat Jan 17, 2015 7:16 pm

MSD can use either logic (points, pertronix, optical, etc.) or magnetic AC VR trigger (MSD distributor, CB magnaspark module).

The wires from the MSD to the coil are 400 + volts so you may want to run those away from low level signals like thermocouples.

For many years back in the 1990s I ran an MSD module in the back of the car and ran the +/- coil wires up to the front of the car to fire the coil on my gas heater. I was running two MSD modules, one for the engine and one for my heater. getting by lol.

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Re: Distance of wire between MSD and coil?

Post by Piledriver » Sat Jan 17, 2015 9:07 pm

My thought was that in the use described, with the MSD near the coil, the MS>MSD box signal is very low voltage/current.
I'd simply use shielded twisted pair or better, StarQuad mic cable. 20-22 ga or even less would probably work fine, its just signal wire.
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