I don't understand how the computer controlled systems work with the MAP sensor getting it's vacuum reading from manifold vacuum not venturi vacuum.
You want a lot of timing advance at low loads for fuel efficiency. But when you open the throttle, increasing the load on the engine, you want less timing. If you kept it at 46deg advance under full load, you'd have a lot of detonation. Not sure why you would increase advance under load.
I gave two examples of the actual LT1 timing map....
2000rpm:
35kPa (20"Hg vacuum) = low load cruise
Advance = 43deg
Open the throttle, and MAP increases. Let's assume it goes to:
45kPa - Advance goes to 41deg
55kPa - 39deg
65kPa - 37deg
75kPa - 31deg
85kPa - 25deg
95kPa (2"Hg vacuum) - 23deg
In effect, as you open the throttle more, the PCM pulls out advance.
Now, as the RPM increases, it puts the timing back in....
For a constant 85kPa:
2000rpm - 25deg
2200rpm - 28deg
2400rpm - 32deg
2800rpm - 35deg
3200rpm - 35deg
3600rpm - 37deg
4000rpm - 37deg
....and so on.
Based on the table, as you open the throttle, and before RPM starts to build, it will reduce the advance by as much as 20deg. Then, as RPM comes up, it will put the advance back in, in proportion to RPM, but if you are watching the timing mark on the damper, as soon as you open the throttle, timing advance is reduced.
My analogy with the older full mechanical distributors was "simplified" to avoid the complication of the ported systems, but the end result is the same.
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