So, the primary ignition system voltage is low, operating on the battery`s 12 volts.
Consequently, the coil, and many other parts, make up this system.
Firstly, all ignition coils, have two set of windings, the primary windings and the secondary windings.
So, to understand how the primary ignition system works, you need to know how a coil works.
The primary coil consists of, several hundred loops of wire. So, as electric current, flows through the wire, it creates, a magnetic field. Changing the amount of current flowing through the wire, will change the strength, of the magnetic field, around that wire. ( We will talk about, the secondary side later )
Older systems use ignition points, that close and open; to turn on and off current, to the primary coil windings. Consequently, the size of the point gap, determined the dwell (ON time). Furthermore, mechanical and vacuum advance units, controlled timing (signal to turn OFF).
Modern systems, use a power transistor, to turn ON and OFF the primary coil windings.
This transistor can be part of the:
- Ignition Control Module.
- Igniter or ICM.
- Powertrain Control Module.
Proper dwell and timing, require sensors, that monitor; engine (RPM), crankshaft and/or camshaft position, engine load, engine temperature, and a knock sensor.
Most engines use, a Crankshaft Position Sensor (CKP) to monitor (RPM) and indicate; which pistons are going up or down. Camshaft Position sensors (CMP), will indicate if the piston is on, compression or exhaust. Manifold Absolute Pressure (MAP) sensors in combination with; Throttle Position sensors (TPS) will monitor engine load. However, most vehicles use, Mass Airflow sensors (MAF) to monitor engine load.
The engine coolant temperature (ECT) and intake air temperature (IAT); will also be used when calculating spark timing. Finally, most systems use a Knock Sensor (KS). The knock sensor is a feedback sensor. Ignition timing, will be calculated; based on the (RPM), engine load and temperature. Consequently, if the timing is too advanced (happens too early); the cylinder will “spark knock” or “Ping”. When a ping or knock occurs, the knock sensor signal; will retard the timing until the knock goes away.
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