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What may seem like a big piece of rubber sitting on top of your spark plugs is actually called an “ignition coil”

And it’s an essential item for making an internal combustion engine work. 

Tune in to discover:

  • What makes an ignition coil work
  • A very basic introduction to electromagnetism – and, more importantly, what it has to do with ignition coils
  • 2 different types of ignition coils


Hello, and welcome to another episode of 30-minute Motorcycling – a podcast for those riders who are at the beginning of their own Dual Wheel Journey, where you’ll discover something new about how your motorcycle, moped, or scooter works – in less than 30 minutes.


And this episode is all about the ignition coil. At first glance, it might seem like just a piece of metal and rubber sitting on top of a spark plug, but without one, your engine wouldn’t run at all. 


In this episode, you’ll find out more about:

  • What the ignition coil actually does
  • What “electromagnetism” is – and what it has to do with ignition coils
  • And, of course, the big question of – “how does an ignition coil work?”


Let’s start at the top – what does the ignition coil do?


Well, think about this – your average motorcycle battery for an internal combustion engine can store 12 Volts of power, right? 


Unfortunately, there’s a little bit of a shortcoming – in order to ignite the fuel and air mixture, there needs to be a spark across the spark plug gap. And in order to do that, you’ll need as much as 60,000 volts.


That means that we’re about 59,988 Volts short. We could solve this problem by installing a bigger battery, but that would fry the rest of your electronic circuits as soon as the ignition is turned on.


Or, we could install an electromagnetic device directly on top of the sparkplug that amplifies the 12 V input from the battery into the 60,000 volts the sparkplug needs.


And the device that makes that possible is the ignition coil – and it’s all possible thanks to a process known in the electrical engineering field as “electromagnetism.”


Now, there are entire books dedicated to this field alone, but as a summary, electromagnetism works like this:


If you wrap a wire into a coil around an iron core or wrap two wire coils around each other, a strong magnetic field will be created, and the electrical charge will increase – which will, in turn, increase electrical current and voltage – all in accordance with Ohm’s Law.


By the way, if you’d like to know more about the concept of Ohm’s Law, I’ve left a link in the episode description to a blog post that goes into more detail.


Either way, that’s how electromagnetism works – now, let’s look at how this makes our ignition coil work. 


An ignition coil has two iron coils – known as the “primary windings” and “secondary windings,” respectively. 

As electricity enters the primary windings from the battery, the voltage begins to increase to around 250 Volts. Then, once it reaches the secondary windings, the voltage is amplified up to either 20,000 volts or 60,000 volts – depending on the ignition coil. 

The reason why the coils for the second windings can create such a high voltage is because of the fact that they turn more often than the primary windings. 

Does it sound confusing? Don’t worry – I’ve included a great video in the podcast episode description from the National MagLab YouTube channel that explains how it all works.

Anyway, there are two types of ignition coils – the canister and the molded type.

The canister type gets its name from the fact that it looks like a metal canister and is more common on older, single-cylinder motorcycles with carburetors. 

There are a few reasons why this type isn’t very common these days. First of all, this type relied on wires to connect to the spark plug – meaning that if one or even both of these wires snapped or got disconnected some other way, the ignition coil would stop working entirely.

But the canister ignition coil is also only capable of producing 20,000 Volts. It might sound like a lot at first, but you’ll have to remember that the average modern motorcycle with fuel injection needs 60,000 Volts to work properly. 

That’s why the molded ignition coil has become more common on modern motorcycles. This type is capable of producing 60,000 Volts – and it’s also more robust and sits directly on top of your sparkplug, eliminating the need for spark plug wires.

As long as the ignition coil stays on, there’s a connection between it and the spark plug.

And that’s what an ignition coil does, a basic introduction to the fascinating concept of electromagnetism and how it all comes together to make that ever-so-vital spark to ignite the fuel and air mixture.

I hope you enjoyed listening and, above all, that you learned something new. 


Until next time, keep your helmet on and your eyes on the road. Bye!