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Dual electronic ignition upgrade on a J?

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Love my surefly, one of the best airplane purchases i've made.  

Lost the field wire on the alternator once,  thing didnt skip a beat even at 8 to 9 volts.

I would install a second with a backup battery, if they let me.  

Edited by McMooney
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9 hours ago, KurtWhite said:

Question about your SureFly installation...did you keep the standard plug gap or did you go more?  I also have one on a 252 and wondering which way is most common.  

I have tempest fine wire spark plugs that i have heard have a nasty tendency to break off the wire if you try to increase the gap. Since the surefly fires on every stroke and the voltages are higher and longer duration, those plugs are wearing out at a faster rate than the plugs on the magneto side so when i rotate sparkplugs i keep the plugs that fire on the surefly on the surefly side just different cylinders as the electrode wears away the gap gets increased naturally from the wear so in essence the spark is getting bigger as the plugs wear out. By the time the surefly plugs are worn out the magneto side plugs will be pre-warned with a bigger gap than new so i will put them on the surefly and just buy 6 new fine wire plugs for the mag side since the mag needs the smaller gap a new plug has compared to the surefly spec. I hear you can buy fine wire plugs with the bigger gap but i had already bought my original finewire plugs before i installed a surefly and didn’t want to waste what i already had. 

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I think surefly says that their unit puts our 20,000V, the same as a Slick magneto.  It is 40,000 for starting. They also have you run the stock plug gap as well.

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If we could eliminate the wasted spark…

(our plugs typically spark twice, prior to the power stroke, and again, wasted one, prior to the intake stroke…)

Would the plugs really wear out at half the rate?  Aka last twice as many hours…?


Plugs are goffle expensive… when purchased a dozen at a time…


Best regards,



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