10.4.8 Microprocessor ignition system
As it has been already said many times, the automotive industry is developing rapidly. Thus, the ignition system with a distributor has been replaced by microprocessor systems. They do not have any rotating and moving elements (see Figure 10.8), but there are ignition coils (increasingly on the coil per cylinder), an electronic control unit (with integrated ignition unit) and a switch (if the ignition coil unit is one) or switches (if there are several ignition coils).
Figure 10.8 Microprocessor spark timing system.
Electronic control unit collects data from a number of sensors. When processing them, the ECU outputs a control signal to the switch (or switches), which determines at what point to ignite the fuel-air mixture inside the cylinder. Each spark discharge is obtained by electronic signals with very high accuracy and without the use of any moving parts. In many engines, a spark is generated not only during the compression stroke (this means that each spark plug generates a spark discharge each time the piston reaches TDC). The content of harmful components in the exhaust gases is somewhat reduced.
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