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Spark Plug Wire Separation & General Knowledge Calling all Experts

gmcjetpilot

Well Known Member
Question: How important is it to separate plug wires from each other and keep plug wires away from grounding metal structure?

What are your thoughts and opinions, experience in general on spark plug wires or harnesses. Do you have a favorite brand or type of spark plug wire?

Looking at pictures of RV builder engine installation's, I see spark plug wires zip tied together and/or running tightly through grounded metal adel clamps with little to no insulation. This applies to EI and traditional Magnetos.

I learned never run spark plug wires together or near grounding metal as a young car enthusiast. With that said OEM spark plug wires in past were not that good. High performance automotive wires are good and even better today. May be space does not matter anymore.

Magnetos traditionally have harnesses with external wire braid, which is grounded at one end. Not sure what the internal core of traditional Champion magneto harnesses use. No doubt braided metal shielding is for RF noise. I suspect this shielding makes spacing issue moot? I have seen plenty magneto harnesses zipped and bundled together. That does not make it right, just food for thought.

Most electronic ignitions forgo external shielding using automotive spark plug wires. However I never heard of Electronic ignitions in EAB kit planes making noise. (fill in blank of half dozen EI brands).
 
Depends a lot on how good the wires are from an insulation standpoint. As you mentioned, modern ones are very good, and I haven't had any crossfire or grounding issues on an airplane since I started flying 23 years ago. What I have had, though, is enough inductive coupling to cause computer issues on low-voltage sensor wires where they are routed close to a spark lead. Devices that typically operate in the 5-volt range are pretty sensitive to the electronic noise that can be generated in close proximity to a spark plug wire.
 

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  • Snap-in Plastic Routing Clamp, 3-16%22 to 1-4%22 ID | McMaster-Carr copy.jpg
    Snap-in Plastic Routing Clamp, 3-16%22 to 1-4%22 ID | McMaster-Carr copy.jpg
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Not an expert but these work well for routing and separating plug wires https://www.mcmaster.com/tubing-supports/snap-in-plastic-routing-clamps/

I used those kinds of spark plug separators and others like them, and then later saw them all zip tied together on an engine at the Lycoming booth - they said that we don't need to worry about keeping the spark plug wires apart any more. It would be great to get a definitive answer on if this is needed or not for future builders.
 
My -6A has been flying the the same Packhard carbon string type HEI leads for 19 years. Some are tie wrapped together for more than a foot. No issues to date.

Suppression type wires and resistor plugs are a must for most microprocessor controlled EIs.

We supply MSD Superconductor or Taylor Spiro-Pro cable with our systems. These both use a inner core wrapped tightly with the conductor perpendicular to it.

Not many problems reported if the terminals are crimped properly on each end.
 
I have become very partial to constructing wire separators 7sing the wrap tie method. Sorry no pixels but you can goggle it.

Quick. Effective. Cheap. Hold any number of wires. Universally available.
 
I have become very partial to constructing wire separators 7sing the wrap tie method. Sorry no pixels but you can goggle it.

Quick. Effective. Cheap. Hold any number of wires. Universally available.
You mean using ZIP TIES to make standoffs or wire looms (with space between wires with additional zip ties). That is a classic, and a good tip.

To Sum It Up:
1) No definitive answer but not likely to be an issue with high quality wires.
2) Spiral wound wires are unlikely to cross fire or ground by proximity
3) EMF field near the spark plug wire can interfere with sensors/probes.
4) Heat and sharp edges to be avoided

Not going to worry, just curious. Thank you everyone. Have a safe and happy Thanksgiving.

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The ties too tight maybe and sharp tie edges may abrade or cut wire, use care.
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>>>IMPORTANT<<<

Got off the phone with MAGNECOR, very nice folks, and they are aircraft people (two Brothers one A&P, one Engeer, and their other company is Electroair EI). This is what I learned about bundling and zip ties on spark plug wires.

WIRE SEPERATORS, zip ties, bundling can be too tight and damage the wire jacket causing a leak (environmentally and electrically). I know some zip ties have sharp edges. As far as trying wires together can do, however crushing, chafing, sharp edges take care. Electroair does recommend and provide wire seperators with their EI, that produces 70Kv at 0.5J. Recall EMAG also has verbage about wire seperators. In my opinion, it can't hurt. Bottom line secure and no abrading of the wires.
 
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