The ignition coil is divided into an open magnetic type and a closed magnetic type according to the magnetic circuit. The conventional ignition coil is an open-magnetic type, the core of which is laminated with a silicon steel sheet of about 0.3 mm, and the core is wound with a secondary and primary coil. In the closed magnetic mode, a core similar to III is used to surround the primary coil, and the outer coil is wound around the secondary coil. The magnetic lines of force form a closed magnetic circuit from the iron core. The advantage of the closed magnetic ignition coil is that the magnetic leakage is small, the energy loss is small, and the volume is small. Therefore, the electronic ignition system generally adopts a closed magnetic ignition coil.
On modern high-speed gasoline engines, an ignition system controlled by a microprocessor has been used, also known as a digital electronically controlled ignition system. This ignition system consists of a microcomputer (computer), various sensors and an ignition actuator.
In fact, in modern engines, both the gasoline injection and ignition subsystems are controlled by the same ECU, using a combination of sensors. The sensor is substantially identical to the sensor in an electronically controlled gasoline injection system, such as a crankshaft position sensor, a camshaft position sensor, a throttle position sensor, an intake manifold pressure sensor, a knock sensor, and the like. Among them, the detonation sensor is a very important sensor dedicated to electronic ignition (especially an engine using an exhaust turbocharger), which can monitor whether the engine is deflagrating or detonating, and as a feedback signal, the ECU command realizes the ignition advancement. The engine does not deflagrate and achieves higher combustion efficiency.