Magneto ignition system
The first type is a magneto. A magneto uses magnets connected to the rotating parts of engine to generate electrical pulses for the spark plug at exactly the right time. This eliminates the requirement for additional battery. Magnetos have become reliable but add weight to the engine. Considering that the magneto does not generate electric for the actual spark plug unless of course the engine is turning, an engine having a magneto ignition system has to be started with an electric starter in the same way a nitro engine does.
Electronic Ignition system
Nearly all RC gas engines on the market today work with an electronic ignition system. This system operates with separate battery to provide electricity for the spark plug. This allows the engine to be hand started. The right time to spark is very important for maximizing the power from any engine. Since the speed of the engine changes, the time that the spark plug should fire for optimal performance changes. An electronic ignition system adjusts the timing according to the engines RPMs.
A magneto engine is set for optimal performance at top speed only while an electronic ignition engine adjusts for optimal performance at all speeds. RC gas engine using an electronic ignition system will usually idle much better and start easier than magneto engines.