Normal

Normal Ignition Timing

As soon as idle speed control stops, normal ignition timing is activated. The ignition timing now depends on engine speed and load.

The ignition must be advanced as engine speed increases because the combustion pressure would otherwise act on the pistons too late and hence reduce the efficiency of the engine.

A load increase means that a larger quantity of air is drawn into the cylinder during each induction stroke (mg air/combustion). This gives rise to a higher gas pressure with the result that the speed of combustion increases. For this reason, the ignition must be retarded when the load increases.

A matrix in the control module's memory contains the ignition timing data for each load and engine speed. The ignition timing is optimized for maximum torque at the engine speed concerned, which also coincides with highest efficiency and, accordingly, lowest fuel consumption.

The "Compensation" articles, explain why normal ignition timing must sometimes be slightly advanced or retarded, as it can also be affected by other factors besides engine load and rpm. See Computers and Controls/Description and Operation/Trionic T7/System Operation, "Compensation." Description and Operation