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Wiring Fundamentals: Ignition Coil Types

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Ignition Coil Types


00:00 - To ignite the combustion charge in the cylinder, the ECU controls an ignition coil which provides enough electrical energy to a spark plug to generate a spark across its electrode gap, initiating the combustion process.
00:12 Your ECU will have dedicated ignition output pins for controlling ignition coils and these will be listed in your ECU's documentation.
00:19 We can break down the common types of ignition coils and their required wiring into three main groups, conventional distributed, conventional direct fire, and internally amplified direct fire.
00:30 There is another type you may come across periodically known as capacitive discharge ignition or CDI ignition coils.
00:36 But they're usually only used in high level motorsport and are outside the scope of this course.
00:41 A conventional ignition coil works by converting a low voltage, high current input into a high voltage low current output.
00:49 Ignition coils consist internally of a primary and a secondary winding.
00:53 And they operate by taking advantage of the inductive load principal we discussed in the electrical fundamentals section of the course.
01:01 The primary winding of the ignition coil is the part your ECU interacts with via its ignition output channels and is simply a coil of wire with a terminal at either end.
01:10 Your ECU allows current to pass through the primary winding and when it requires a spark to occur it removes the ground connection from the circuit, stopping the flow of current abruptly.
01:21 As this primary winding is an inductive load, this generates a voltage spike, typically in the range of 200-300 volts.
01:28 The secondary winding of the coil then converts this voltage spike up to a much larger voltage.
01:34 Typically in the range of 20000 to 40000 volts which it then applies to the spark plug gap.
01:40 This voltage is high enough for a spark to jump across the gap which ignites the combustion charge.
01:45 The primary winding of the ignition coil requires a large current to flow through it to build up enough energy for the secondary winding to generate a spark.
01:53 Generally the ECU is not capable of handling this level of current directly and will use a device called an ignition amplifier.
02:00 These are sometimes known as igniters or ignition modules but they all perform the same task.
02:05 You can think of them in the same way as a relay except that their solid state electronics are capable of switching on and off much faster than the mechanical switch system in a conventional relay.