Adjusting the ignition timing angle (Fiesta 4)

Depending on the load condition (idle, partial load, full load) and the air quality, the fuel mixture burns in the combustion chambers at different speeds. In order to use the fuel energy most efficiently, the control unit changes the ignition timing depending on the load condition for each individual cylinder. The best time for the ignition timing is when the fuel-air mixture ignites at the moment of highest compression. In a four-stroke engine, this is the moment at which the piston wants to switch from the forward motion in the compression stroke to the reverse motion in the power stroke.

Ignition timing

Theoretically, the ideal ignition moment is the moment at which the piston begins to move downwards, since the compression of the fuel mixture in the cylinder is maximum and the piston is subject to force from the combustible fuel mixture. However, in practice, approximately 3 ms pass between the initial moment of ignition of the fuel mixture and its complete combustion. Therefore, the formation of a spark should occur somewhat earlier than the piston reaches TDC, which will allow for optimal combustion under all engine operating conditions, since the pressure from the combustion of the fuel mixture acts on the piston after it has passed TDC. Thus, the ignition moment is moved to an earlier date, called the ignition advance angle.

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