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Old 06-13-2018, 07:56 AM
j-red j-red is offline
Join Date: Dec 2015
Location: Lewes, DE
Posts: 210

I ran the Autolite 386's gapped around .030
Changed them about every 50 hours, but not because they were functioning poorly: just because they were cheap.
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Old 06-13-2018, 06:01 PM
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G3i Ignition G3i Ignition is offline
Join Date: Aug 2009
Location: Littleton, Colorado
Posts: 182
Default KV vs's Gap, 1 foot?

Jump a foot, really, maybe in a vacuum chamber? It takes 60K average to ionize 1.00" @ standard pressure & temperature. X12, do the math

Originally Posted by FasGlas View Post
Not uncommon in racing engines to run magnetos and auto plugs, I have many times.. But, the heat ranges are different, the application is different and the plug life is short. Aviation mags have far less output than auto racing mags. Racing mags can jump a much larger gap. I've seen them jump over a foot on the test stands. The smaller auto plugs would be more susceptible to lead fouling with an aviation mag, not so much with an EI. Not a lot of pros to the cons.
Thomas Shpakow

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Old 06-13-2018, 06:22 PM
CDN CDN is offline
Join Date: Nov 2011
Location: Calgary, AB
Posts: 75

I used the G3 ignitions instructions to modify one of my bendix s-1200 mags. The other ignition is a CPI from SDS. I run NGK BR8ES plugs on both ignitions, .018 gap on the ones for the mag and .032 on the ones fired by the EI. I swap the plugs out every 100 hours after I perform a compression check and cylinder borescope.

I now have over 200 trouble-free hours and I'm on my third set of plugs. I dont throw them out because they are worn, damaged or fouled. They're so cheap it just makes sense to replace with new after they are removed for the scheduled maintenance. The plugs fired by the mag look the same as the ones for the EI except for the gap.

Before this I ran a similar setup on an O-360 in my Glastar before going to dual pmags. I had successful service for over 400 hours.

BTW the G3 instructions are cheap insurance for getting the mod done correctly.
VAF Donation made Feb 2018
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Old 06-13-2018, 06:26 PM
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FasGlas FasGlas is offline
Join Date: Mar 2014
Location: Prescott, AZ
Posts: 487

Yup.. Believe it or not. I used to get Vertex mags beefed up at Don Zig Magnetos for race engines. After the mag was finished it's put on a test machine that clamps the mag and rotates the shaft. The 8 wires went to 8 spark gaps that had a pull handle on one set of gaps. They start the machine and pull the handle to test the output of the mag. The difference between a stock Vertex and a Don Zig Vertex was amazing. And yes, it would jump a foot gap right out in open air. Looked like a Jacobs ladder. Aviation mags..... Well, maybe an inch or two.
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Old 06-13-2018, 08:35 PM
Gerald Loyd Gerald Loyd is offline
Join Date: May 2006
Location: Dumas, Arkansas
Posts: 63

Hello Thomas

Thanks for sending the G3i module. I installed it this afternoon and got a good mag check. I didn't get to test fly it because of weather. I'll do it in the morning & call you.

Gerald Loyd (Bulldog)
O-320, Catto 2 blade
Began flying 1963
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Old 06-13-2018, 10:01 PM
Join Date: Mar 2008
Location: Seattle
Posts: 1,364

I purchased the Bendix 'Old Style' ignition harness plate (has gland nuts holding the wires) from an eBay ad, it easily adapted to 8.5mm MSD spiral core wire & 90 degree boots.
It fired BR8ES plugs gaped to .016 just fine.
Scott Emery
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
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Old 06-14-2018, 05:05 AM
vic syracuse vic syracuse is offline
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Join Date: May 2005
Location: Locust Grove, GA
Posts: 2,265
Default High resistance

Some of the auto plugs, such as the BR8EIS have very high resistance, about 5K ohms. Isn't that hard on the mags, especially the coil?

The Autoilite 386's are not resistor plugs, and do not have high resisitance.

Vic Syracuse

Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES
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Old 06-14-2018, 06:16 AM
j-red j-red is offline
Join Date: Dec 2015
Location: Lewes, DE
Posts: 210

And no plug adapters are needed for the auto lite 386 either.
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