Ignition Timing on most of the standard platforms is very simple. The strategy heavily relies on the knock control system to interpret knock sensor data and adjust ignition timing in real-time.
The final ignition output is a simple equation based largely on the base ignition table and knock control system.
Ignition Table Value + Knock Ignition Limitation Value - Knock Retard Value = Final Calculated Ignition Timing
It then compares the Final Calculated Ignition Timing and the original Ignition Table Value and chooses the lesser of the two.
Keep in mind that items like IAT ignition correction can also be added to the Knock Ignition Limit Table Value in the background.
These are the three major data items to pay attention to in order to follow the basic knock control system and final ignition timing.
Say in this example that we have an Ignition Table Value of 21.0 degrees and a Knock Ignition Limitation Table Value of 2.0 degrees.
21 + 2 = 23 degrees
Knock Retard is a product of the Knock Control Value multiplied by the Knock Retard Table Value. Take the example in the datalist above.
.38 x 10 = 3.8
Because Knock Retard is logged as a rounded value it will show in logging as 3.5. Keep this in mind.
So the final value is 23 - 3.8 = 19.2.
Because the Actual Ignition Value is logging as a rounded value on OBD platforms it will show as 19 on those platforms. Keep this in mind.
