Magnetos always fire the spark plugs at the same point-on the order of 25 degrees before top dead center (TDC)-and rely on the combustion event to carry on by itself to reach maximum pressure by the time the piston reaches 11 to 17 degrees past TDC. Mags put out a spark of on the order of 12,000 volts. The downside: At 500 hours it's time to pull mags for inspection and repair or replacement. That's not cheap.
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