Originally Posted by
the Wasp
wow, you sure can't complain about that can you
A virtue of spark ignition is the timing is fixed (excepting the desired rpm advance), whereas glow ignition has the timing influenced by mixture where a lean mixture can cause the timing to advance quite far, causing some issues with detonation, increased temperature and even a spitting a prop.
This virtue aids in providing resistance to engine flame out due to too lean a mixture. Conversely, a rich mixture that sometimes will cool off a glow plug, only causes lowered power with spark ignition.