This is a good thread, but I wonder whether it should be split up. Some of the posts are about transistorized kettering systems, and the rest are interested in true CDI. A few are even interested in computerized timing advance. Looking back on this thread, when the electrical engineers among us start discussing CDI and computers, someone will pipe in with a question about TIM6 or modelectric coils. Neither camp is being well served: the kettering types are confused and the CDI'ers are distracted.

One of the hurdles to communication and understanding is that those following the kettering path probably don't even know what kettering means...

Another distinction needs to be made. If the goal is to putter around and learn about the workings of engines, then scratch-build. If one prefers to have a reliable, quality, economical high-performance solution and to spend time flying the engines, then by all means purchase the packaged solutions (e.g. CH ignitions). To those in the second category: let us dedicated scratch-builders and tinkerers waste our time and money with our handfuls of DigiKey parts. No more chiding us to go out and buy the CH!

That said, shall we start a new CDI-only scratch-builders thread?