Auto Plugs with Mags

[Gerald Loyd]

I never hear about anyone using auto spark plugs with magnetos. Why not use them. A set of 8 auto plugs cost a lot less than one aircraft plug.

[jibby212]

My Volkswagen powered aircraft used auto plugs and a mag, I think I heard somewhere that the electrode needed to be larger to keep a more consistent gap due to the close gapping of plugs used with a mag and the electrode wear. Im sure we will get a real answer here soon.

[Weasel]

This guy makes a setup for what you are looking for.


As far as I know if you gap the plugs to the magneto requirements and keep the lead cleaned out, the auto plugs should work fine.

[pjoshyjosh]

many have Engines with 4 auto plugs on an Electronic Ignition. But the other 4 Aviation plugs on the Magneto.

[FasGlas]

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.

[j-red]

I purchased the components and instructions from G3i which is linked above, and ran 18mm auto plugs from a standard Slick mag. Worked flawlessly. If you have any questions, I can try to answer them, but it?s a pretty simple conversion.

[Gerald Loyd]

Thanks guys. I have all the components to do it, but didn't know if anyone was using auto plugs with mags . Unless someone gives me a good reason not try it, I'll go ahead with the project.

[Gerald Loyd]

j-red

Are you gapping your plugs at .026?

[vetterman]

My experience with the G3I setup has been positive for many years. Both the -7 and the cub have Bendix mags. These two planes have @600 hours with this setup and have a steady diet of avgas with no plug fouling or any other problems. I use the Denso IK27 iridium plugs gapped at .022-.023. I change them at 200-250 hours but I?m not sure that is necessary. $8.50 for an iridium plug sure beats $30 for a regular massive electrode aircraft plug.

[Weasel]

If you go with all of the G3i parts to make the ignition system, you should gap the plugs per G3i recommendation. If you only use the wire harness conversion, you gap per magneto specifications which will be a smaller gap.