Many cars with hall effect distributors can use that signal to feed an ecu and control timing as well, so the split would not be defined by distributor or not. It would be old mechanical distributor or not. Of course those can be recurved to create custom timing advance maps.
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Yes this is what I was getting at. For example an old Honda with a vacuum/ mechanical advanced vs. a newer Honda where the distributor just distributes the spark and the timing is done via the ECU.

Like the other potentail gains from such a system, I would be interested in seeing data of any gains/results from total timing control in race lap times that folks can share. I expect this would matter more for rwd cars that spend more time modulating the throttle. When I am racing I am at the full load/advance state all the time, or I just screwed something up, so I run fixed timing. It would run a bit better in the paddock with programable timing though. :P
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Does not matter if you are a WOT all of the time. You will still not be able to optimize the advance as the vehicle will be going through the RPM band, and through different loads (2nd vs 4th etc.). Also you can take advantage of running more timing when the engine is cool (begining of a race) vs. hot, vs. intake air temp etc. With fixed timing you would not be able to realize these gains. To me these gains will be greater than just controlling fuel alone.

This is why I am more interested in what Andrew pointed out, and if this is legit.