Timing advance guru input needed
I don't trouble myself with EFI so forgive me a little here.
All the same principles apply.
As rpms climb, lead time in degrees is needed because the engine is turning faster and there's less time (seconds).
As efficiencies build, the combustion itself speeds up, reducing the amount of additional lead needed in the upper rpms.
from MTSC 1959
On your table, the left is presumably MAP.
So when looking at timing from traditional analog control, it will be discussed as vacuum.
So, 105 kPa is atmospheric or for purposes, wide open throttle.
and 40 to 60 kPa should be low throttle, steady cruising on a flat highway or interstate.
The engine should be running leaner than at idle or WOT.
Finally between 80 and 60 kPa is throttle is opened further, and in this range will be when the leanest mixture will make the most power.
Lean mixtures take more time for the flame to travel. So this is when the most lead time is needed.
from MTSC 259. Ignition system analysis. 1969
This lead time for lean mixtures (vacuum advance) needs to be removed as the mixtures go rich again approachin gwide open throttle.
That's the basics of it.
^^^^^^^^This^^^^^^^^^^^
I don't trouble myself with EFI so forgive me a little here.
All the same principles apply.
As rpms climb, lead time in degrees is needed because the engine is turning faster and there's less time (seconds).
As efficiencies build, the combustion itself speeds up, reducing the amount of additional lead needed in the upper rpms.
from MTSC 1959
On your table, the left is presumably MAP.
So when looking at timing from traditional analog control, it will be discussed as vacuum.
So, 105 kPa is atmospheric or for purposes, wide open throttle.
and 40 to 60 kPa should be low throttle, steady cruising on a flat highway or interstate.
The engine should be running leaner than at idle or WOT.
Finally between 80 and 60 kPa is throttle is opened further, and in this range will be when the leanest mixture will make the most power.
Lean mixtures take more time for the flame to travel. So this is when the most lead time is needed.
from MTSC 259. Ignition system analysis. 1969
This lead time for lean mixtures (vacuum advance) needs to be removed as the mixtures go rich again approachin gwide open throttle.
That's the basics of it.
