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Wiring Fundamentals: Ignition Coils

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Ignition Coils

04.42

00:00 - In a conventional coil distributed ignition system, there will be a single ignition coil and a single channel ignition amplifier.
00:07 The ECU triggers a spark from the single coil every combustion event, which is then directed to the required cylinder via the distributor rotor, cap and HT leads.
00:17 For engine with eight or more cylinders, this can become a problem at high engine speeds.
00:22 The time between combustion events becomes very short and may not be long enough for the coil to build up enough energy to generate a powerful enough spark for the next combustion event.
00:31 If you strike this problem, your best course of action is to move to a direct fire ignition system, detailed in the following course sections.
00:38 A conventional coil distributed ignition system will have a single coil with a positive and negative terminal and an ignition amplifier that typically has three terminals.
00:48 The coil positive terminal is supplied with 12 volts from the power supply system when the engine enable switch is on or the key barrel is in the on position.
00:57 The negative terminal is connected to the high current input pin of the ignition amplifier.
01:03 The ignition amplifier will also have a high current output pin which is connected to a good grounding point on the engine block, and a signal input which is connected to an ECU ignition output channel.
01:14 There are many different models of ignition amplifier out there though and you need to be sure of the pin out for your particular model.
01:20 Your ECU manufacturer should be able to help out with this.
01:24 A conventional coil direct fire ignition system does away with the distributor and instead of the single coil providing the spark for every cylinder, there's now an individual coil for each cylinder.
01:34 These coils may either be mounted close to the spark plug and connected via a short HT lead or mounted directly on top of the spark plug, eliminating the HT lead, which is known as a coil on plug installation.
01:46 An ignition amplifier for each coil is now required and they're usually combined into a single package known as a multiple channel ignition module.
01:54 Each ignition coil will have a positive and a negative terminal.
01:57 The positive terminal is supplied with 12 volts from our power supply system when the engine enable switch is on or the key barrel is in the on position.
02:07 The negative terminal of each coil is wired to the corresponding high current input pin of the multiple channel ignition module.
02:14 The ignition module will most likely have a single high current output pin which is connected to a good grounding point on the engine.
02:21 The ignition module passes the current from all the coil negative pins out of the single high current output pin to the engine block.
02:29 The ignition amplifier will also have one signal input pin per channel, which is wired to the corresponding ignition output channel of the ECU.
02:38 Once again there are many multiple channel ignition modules in use.
02:42 And you need to confirm the pin out of the one you have.
02:44 Either from factory documentation or contact with your ECU supplier.
02:49 There is a variation on the direct fire ignition system it's good to be familiar with.
02:53 Which is known as a wasted spark ignition ssytem.
02:56 In a wasted spark setup, each coil will have two secondary winding high voltage outlet terminals that are connected to spark plug and two companion cylinders.
03:06 Companion cylinders are ones where the piston positions are the same but the phase is 360 degrees offset.
03:12 This way, when the spark is generated at both plugs, one cylinder will be at the top of its compression stroke and combustion will be initiated.
03:21 The other will be at the top of its exhaust stroke and the spark will be wasted.
03:26 This system requires half the number of ECU ignition channels compared to a true direct fire system and is commonly used by OEM manufacturers to reduce cost.
03:34 An internally amplified direct fire ignition system is very similar to the conventional coil direct fire ignition system.
03:41 It has one coil per cylinder, either connected to the spark plug via a short HT lead or mounted directly on top of the spark plug.
03:49 The internally amplified system does away with an external ignition module however by moving it inside the coil itself.
03:56 This offers great flexibility as each coil is now a completely contained unit and can be used on any configuration of engine.
04:03 An internally amplified ignition coil will typically have three or more pins.
04:07 Two of these will be its 12 volt supply and high current engine ground.
04:12 The third will be a signal input wired to the ECU ignition output channel.
04:17 Internally ignited coils frequently have more pins that this however, including signal ground reference connections, and ignition system feedback pins, plus others.
04:26 If you're using aftermarket performance ignition coils, you should have been supplied documentation with them.