Normal ignition timing
As soon as idle speed control ceases, normal ignition timing will be activated. The ignition timing is now dependent on the engine speed and load.
Ignition must be advanced further as the engine speed increases, as the combustion pressure would otherwise act too late on the piston and reduce the efficiency of the engine.
An increase in load means that a larger air mass is drawn into the cylinder during each induction stroke (mg air/combustion). This gives rise to a greater gas pressure, which means that the combustion velocity increases. Because of this, the ignition must be retarded as the load increases.
The ignition timing for each point of load and engine speed is written into a matrix in the control module memory. The ignition timing is optimized for the maximum engine torque at the point in question, which also coincides with the best efficiency and thereby the lowest fuel consumption.
The following text explains why normal ignition timing must occasionally be advanced or retarded slightly, as factors other than load and engine speed can affect it.