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Spark plug wire installation - distance between wires

 
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BARRY CHECK 6



Joined: 15 Mar 2011
Posts: 730

PostPosted: Tue Jul 24, 2018 8:49 am    Post subject: Spark plug wire installation - distance between wires Reply with quote

Micky:
In the old days and even going back to old cars, the space was needed to prevent cross-over ignition of the spark.
Today, with higher dielectric wires, shielded wires and silicon coated wires the need for separation in no longer needed.
We are talking Spark Plug Ignition Wires...  There IS a need for separation between Ignition wires and other wires such as EGT & CHT probes/harnesses.  How much separation?  I can't say.  Maybe the EGT/CHT manufactures state how much in their install manual.
Barry
On Tue, Jul 24, 2018 at 2:45 AM, Mickey Coggins <mick-matronics(at)rv8.ch (mick-matronics(at)rv8.ch)> wrote:
Quote:
Hi,
I've always heard that spark plug wires need some small distance between them, and that's what I did on my engine, but I'm curious what happens if you don't have distance between them.  I've seen several certified aircraft where the wires were just zip tied together with no spacing, and they seem to fly.  Smile
Example I just saw on Reddit:
https://i.redd.it/o4e5rmjqktb11.jpg

Thanks,Mickey Coggins



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PostPosted: Tue Jul 24, 2018 9:10 am    Post subject: Spark plug wire installation - distance between wires Reply with quote

My problem with the wires bundled together approach is that the zip ties are very sharp edged when pulled tight and did cut into the wire insulation over time. This caused an arc over on two adjacent wires over the 1,000 hours time in service on an ElectroAir system that developed this problem. This problem was elusive until I started moving the bundle around with the engine running. The zap I got, got my attention...
The picture below is similar to my solution. I did the same thing on a 502 powered Chevelle I have that has an MSD 5 with CDI ignition.
Ed
[img]?ui=2&ik=fac9030c21&view=att&th=164cd379b1eb80dd&attid=0.1&disp=safe&realattid=ii_jjzxyd1d0_164cd379b1eb80dd&zw[/img]


On Tue, Jul 24, 2018 at 12:36 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
At 01:45 AM 7/24/2018, you wrote:
Quote:
Hi,

I've always heard that spark plug wires need some small distance between them, and that's what I did on my engine, but I'm curious what happens if you don't have distance between them.  I've seen several certified aircraft where the wires were just zip tied together with no spacing, and they seem to fly.  Smile

Example I just saw on Reddit:

https://i.redd.it/o4e5rmjqktb11.jpg

Thanks,
Mickey Coggins

   I cannot imagine the physics supporting such an
   assertion.  Engines running legacy magnetos are
   generally fitted with shielded plug wires. Two
   wires tied to each other are DOUBLE shielded
   for what ever effect the writer is hypothesizing.

   Modern electronic ignitions can use automotive
   unshielded wire . . . so without shielding, what
   is the effect of having two or more wires running
   in close parallel for some distance?

   Electrostatic coupling (the physics thingy that
   calls for shielding) is very weak. The energy
   coupled between adjacent wires is a tiny fraction
   of that flowing in the wire from ignition source
   to the plug . . .

   Lacking competent analysis and/or repeatable
   demonstrations of deleterious effect, I'll bet
   this is yet another ol' hangar yarn . . .
  




  Bob . . .


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