Ignition Systems - How they Work | SCIENCE GARAGE

(engine revving) - You love the rumble of an engine, and that's 'cause there's combustion goin' on in there! But none of that'd be possible, without the one little guy that makes it happen. Today I'm talkin' about spark plugs!

(upbeat music) Hey, gang. I hope that intro sparked your interest. (laughing) We're talking about my fourth favorite thing in the world, right behind James, (screaming) Nolan, and pork rinds. These things are a modern car's link to the past.

As engines, and your vehicle's electrical system gets more and more complex, and the robot uprising draws close, you can still go old school, get under the hood and change your own spark plugs. Feels good to still be able to have something you can do

in your car without needing a computer science degree. The first spark plug was used in 1860, by Belgian engineer John Joseph Etienne Linnoir. He used the electric spark plug in a gas engine he invented,

the first internal combustion piston engine, or some people say it was invented in 1839 by Edmund Berger. It's a controversy, and we all know, controversy's full of sparks. (ding)

Right now, you're probably asking yourself, "I wonder how spark plugs work, "and how Bart gets his teeth so white." Well, the second one's easy. I brush 'em. (laughs) The spark plugs are a little bit more complicated. We know that a spark plug sparks,

to ignite the air/fuel mix in the chamber, and drive the piston down. A four cylinder car's got four spark plugs, the six cylinder car's got six spark plugs. Flintstone's cars don't have spark plugs, just your feet.

Maybe if you're rich, a dinosaur that occasionally turns to the camera and says, "Eh, it's a living!" (laughter) Oh, and some engines, like the infamous Dodge Hemi, uses two spark plugs per cylinder. And if you're not sure if you've got a Hemi,

a good way to tell is to think back, if anyone ever came up to you and said, "Hey, you got a Hemi in there?" And you said, "Sure do!" Then you probably have a Hemi. Alright, let's head to the store,

grab one, see what's in it. (whooshing) (tapping keys) - Welcome to Pep Boys.

How can I help you? - Nolan? What are you doing here? - I'm Anthony, actually. I must have one of those faces. - Yeah, you look like a guy. Can I get a spark plug, please?

- Sure, what kinda car? - Doesn't really matter, the car, I just want a spark plug. - [Anthony] Hot or cold? - I should talk about that. Look, I got like, a show where I tell people how stuff works,

so I really just want one spark plug. - Okay, great. I'll get a spark plug. - Thanks. I'll be right back. - [Bart] Thanks, man.

- Alright, well, here's a spark plug. - [Bart] Thanks, buddy. - You're welcome. Have a great day. (whooshing)

- Great guy. Alright, so the connector, or terminal, is at the top of the spark plug. This is where the wire attaches. It connects, inside the plug, to the copper core

at the center of the electrode, which is surrounded by insulation. Next is the hex head. This is where you put your socket, which fits for tightening and loosening the plug, when you're changing these jabronies out.

Now below that's a gasket that compresses tightly against the cylinder head. That keeps it from moving. Some plugs have a tapered seat, without an additional seal here. So the bottom half of the plug is threaded, and that part gets screwed, must be nice.

A tiny bit of the center electrode juts out of the plug's lower end. Hey, been there, man. And the whole thing is capped off with a ground electrode, or ground strap. The spark that makes the engine run

jumps the gap from the very end of the center electrode, to the ground electrode. This is what ignites the air/fuel mixture that's been compressed by the piston. So effectively, we've got insulated metal,

running from this tip to this tip, separated from what'll attach the engine, and the ground. To complete a circuit, it's gotta arc. The ground electrode is made of metal,

and comes in several shapes, from notched, or Y shaped electrodes, to triple electrodes, with three little arms that reach for the tip of the center electrode. The spark is caused by a momentary surge of high voltage,

which could reach 20,000 volts to 25,000 volts. We know that these bad boys ignite the fuel, but they can also play a role in dissipating engine heat. A spark plug's ability to transfer heat

away from the ignition chamber, based on the length of the insulator nose, and the materials used for the center electrode, and the materials for the insulator. Most often, you've got a copper center electrode core,

surrounded by a nickel alloy, which you can see at the tip of the plug. Inside the plug, the center electrode's encased in porcelain. The porcelain makes sure the spark happens at the tip,

but it also plays a role in heat transfer. The terms for these different spark plugs are either hot or cold. Cold plugs have less insulation close to the tip, and with less insulation, more heat can be

transferred away from the combustion chamber, to the outside of the engine. Fancy spark plugs use platinum or iridium, which have higher melting points, and are a little pricier. Must be nice. So why would you want a hot plug?

Because you're drivin' a normal car. Hot plugs have more insulation, which keeps the plug's temperature high enough to burn off carbon deposit, and that allows for more time between spark plug changes.

Hey, let's get back to the metals in the spark plugs. Copper spark plugs have a solid copper core, but the business end of the center electrode's actually a 2.5 mm diameter nickel alloy.

That's the largest diameter electrode of all the spark plug types. The smaller the diameter, the less voltage is required to initiate the spark. Nickel alloy is also softer

than either platinum or iridium, so the sharp firing edge you get, right out of the box, tends to wear out more quickly. Despite those shortcomings, copper spark plugs are still a good choice for certain applications.

They're best for older, like early 80's and earlier, vehicles, with low voltage distributor based ignition systems. You don't use copper spark plugs in high energy distributorless ignition systems,

or coil on plug ignition systems, 'cause they wear out too quickly. There's one exception to that advice. Some late model, high performance engines were designed specifically for copper spark plugs.

In those cases, copper spark plugs are considered to be high performance spark plugs. If your owner's manual calls for copper spark plugs, don't upgrade to platinum or iridium. You're gonna screw it up!

A single platinum spark plug is basically styled after a copper spark plug, with a platinum disc welded to the tip of the center electrode. Since platinum's harder than nickel alloy,

it holds that sharp edge for as long as 100,000 miles. Platinum spark plugs also run a bit hotter, preventing spark plug deposit build-up and fouling. Platinum spark plugs are usually

the best spark plugs for newer vehicles with electronic, distributor based ignition systems. If your owner's manual recommends platinum spark plugs, don't downgrade to copper spark plugs to save a few bucks.

Upgrade to either double platinum, or iridium spark plugs. Spend a few bucks. Alright. Buckle up, 'cause we're getting to iridium. (laughs) Iridium is harder than platinum, and in most cases,

iridium spark plugs last about 25% longer than comparable platinum spark plugs. Because iridium's costly, iridium spark plug manufacturers reduce the diameter of the center electrode, to as little as .4 mm.

In addition to saving money, the fine wire center electrode on iridium spark plugs increases firing efficiency. Many car makers require iridium spark plugs, or iridium platinum combination spark plugs,

for coil on plug ignition systems, or multi coil ignition systems. If your owner's manual specifies iridium spark plugs, don't downgrade. They're not gonna perform as well.

We talked about the different shaped electrode heads, and what do they do? You know what? Let me go back and get some other plugs. (whooshing) (phone ringing)

- Thank you for calling Pep Boys. This is Nola, uh, Anthony. - Hey. - Let me put you on hold. Alright, bye. Welcome back.

- I'm gonna need like, three more spark plugs, if I could. - Three more spark plugs, comin' up. (whooshing) Alright. Some manufacturers claim premium spark plugs

are gonna increase your gas mileage. That's true-ish, to a point. The National Institute for Automotive Service Excellence indicates bad spark plugs can decrease fuel economy by up to 30%, cost drivers about 94 cents a gallon,

at today's prices. If a car's gas mileage suddenly drops, there's a good chance it's 'cause misfiring spark plugs. So what does most for your mileage is making sure you got the appropriate heat rating

and gap between the center electrode, and the ground electrode. Gap? Yeah. This distance is the gap, and it's different for different OEM specs, but generally, in cars with lower compression ratios,

and a leaner air/fuel mix, the gap can be larger, in an effort to allow the spark to come into contact with more of the mix. In higher compression engines, it's more often smaller,

because everything's so tightly squeezed together, and the timing of smaller spark can be more exact. We talked about the crazy voltage needed to create a spark. So, if you take a look over here, you'll see my hand.

But, if you look downward, you'll see it's pointing at an ignition coil. An ignition coil is an induction coil in a car's ignition system. It transforms the battery's low energy

into the thousands of volts needed to create an electric spark in the spark plugs, to ignite the fuel. It's essentially high voltage transformer, made up of two coils of wire.

Let's get in there! One coil of wire is called the primary coil. Wrapped around it, is the secondary coil. The secondary coil, normally, has hundreds of times more turns of wire

than the primary coil. Current flows from the battery through the primary winding of the coil. The primary coil's current can be suddenly disrupted by the breaker points,

or by a solid state device in electronic ignition. - Hey. - Dude. - That looks like an electromagnet. - You're right. It is an electromagnet, but you can't keep just barging onto set.

- Why not? - I'm shooting a science show. - Alright, fine, I got stuff to do anyway. I don't need you, Bart. - Alright. Good, remember it next time. Well, he's right. It is an electromagnet, but it's also an inductor.

When the circuit is suddenly broken by the points, the magnetic field of the primary coil collapses rapidly. The secondary coil is engulfed by a powerful and changing magnetic field.

This field induces a current in the coils, high voltage current, because the number of coils in the secondary winding. The secondary coil feeds this voltage to the distributor,

by way of a very well insulated, high voltage wire. This high voltage wire is connected to a distributor, which is either electric or mechanical, and if it's mechanical, it's connected to a rotor

that sits inside the distributor, to give the energy to the appropriate plug. It's a distributor cap. I shoulda just got one, when I was at the store. What am I doin'? You know how when you're fixin' your car,

and you gotta make all these trips? I'll be right back. (whooshing) - Uh, I'm also gonna need a ignition coil, a distributor, and ignition cables, if I could.

- Alright. Can do. (whooshing) I dunno. He's a lot more enthusiastic than Nolan. So, we talked about what's in the ignition coil.

It is going to send a charge to the distributor cap. This distributor cap is going to distribute that current to one of these four spark plugs. The energy's gonna want to complete that circuit,

so the spark is gonna jump that gap, and ignite the air/fuel mixture. Let's take a look at what's inside. So when the head of the rotor is close to the conducting piece on the head of the distributor,

this is touching. That makes sure there's a current that can get to the spark plug. When it's in between, there's no current flowing, just to make sure it doesn't go jumping to the wrong plug.

So all cars have a variation of an ignition system like the one I just showed you. Right here, is a resistor. This is gonna take the amperage down, so you're not getting the full power from the battery.

If we follow this cable, we can see we're hooked up to the top of our distributor cap. That distributor cap has the rotor inside, like you saw, which gets spun by the engine.

When that rotor moves, it hits one of these spark plugs, and gets distributed to these four plugs, firing the engine. It's pretty cool. Let's go take a look at Tony Angelo's car,

to see how it's different. So, if this were a factory, late 70's Malibu, we'd see a big ol' distributor cap, sittin' back here, and it would be sending

eight different ignition cables to the spark plugs. What we have on this is electronic timing, and each spark plug has its own ignition coil.

So it used to be, that the distribution, and ignition timing, was determined by mechanical timing, and every once in a while, you could just advance, or retard it, by twisting the cap, and that'd move the contact points

in relation to this whole mechanism. Today, the distribution's determined by your car's ECU, and it can be advanced or delayed, depending on demand! Alright, well, we did a cool demo, sparks flew,

and I made a new friend. Spark plugs! Please subscribe to Donut. All you gotta do is click in this little yellow globe. It's how we get to make new shows. Wanna know more about ECUs and ignition timing, check out this Science Garage on tuning.

Oh, you know what's got a bunch of spark plugs and uses a Hemi? This Demon. Check out the Up to Speed. And we got some merch. Head to shop.donut.media, follow us on Twitter and Instagram, @donutmedia, follow me @bidsbarto.

Don't tell my wife how many trips I made to Pep Boys.