This is all it says on timing control.........
Q: How do you control the timing of a SmartPlug? Back to top
As an engine speeds up and slows down the timing of when ignition takes places must also change. If not, the fuel may ignite too soon causing pinging (that awful noise you hear under your hood). This is very hard on the engine. If the fuel ignites too late, you lose power. This is very inefficient. For engines that run at a constant RPM, a specific SmartPlug is built for optimum performance at whatever the given RPM is. For engines that have variable timing, the SmartPlug system is equipped with a electronic circuit to change the timing. This device is called a timing controller.
There is also a link to a NASA technical paper on the ignition system, and reviews by flight magazine