Working principle and types of spark plugs

Working principle and types of spark plugs

What is spark plug? ➤ How spark plug works ➤ Types of spark plugs ✅

The car is able to move forward by a combination of parts working together to achieve this process. The ignition is one very important part the enables a car to start. From the time automobiles were invented, there have been spark plugs always, as a key part of gas engines.

These are parts used to conduct the electrical energy from the ignition system of your vehicle that completes the combustion process. High pressure is needed to ignite with a bolt of lightning from the spark plug. This pressure is produced as a result of compression of gas in the cylinder head. This ignition creates an explosion forcing the cylinder downside.

Except for diesel engines, they don’t need spark plugs because they run at higher ratios. This means they can create enough combustion without the need of any spark. Many of the classic cars and some modern ones feature one spark plug for every cylinder. Other high performance cars on the other hand have two on each cylinder.

Spark plug covering features an electrode in a visible porcelain shell with insulation. A heavily insulated wire is connected to it. The spark plug acts as a central part of the ignition system.

What is spark plug?

From the explanation above, you can denote that the spark is an integral part of the ignition system .it’s important to fully understand what it’s all about. When you hit the ignition, a highly combustible mixture of air and oil is compressed making it highly flammable.

In order for the engine to start, this mixture is supposed to be changed into mechanical energy. As you may already know, a car requires electrical energy to start. The spark plug is responsible for providing this energy.

The plugs produce a lightning spark to start the engine. Then when the highly compressed air mixture from the head cylinders gets in contact with the spark, it produces an explosion that forces the piston down. It’s obvious that the spark the part of the ignition system responsible for starting your car engine.       

There are several types of spark plugs on the market today. Each types of designed for specific types of car.

Now that you understand what a spark plug is, we can discuss some of its options

How spark plug works

It is very easy to understand how spark plug works, based on the explanation above. The centre electrode connected to the ignition coil is responsible for a spark plug working.

The spark plug simply produces as spark, like that from a match stick to ignite spark-ignition engines. It has two major functions in your engine:-

● Air/fuel mixture ignition:-This happens when electrical energy is transmitted through the component. It becomes the conductor for the electricity needed to start the engine. This power jumps the gap in the firing end of the plug. The voltage supplied must be high enough to hit the compressed mixture in above the cylinder head.

● Removing heat from the combustion chamber:- There is usually a lot of heat in the combustion chamber after the fuel has been ignited. Such heat can alter the proper working or the pistons and the whole engine, and therefore must be eliminated. Spark plugs do not create heat, but they are used to eliminate it.

The spark plug in this regard simply becomes a heat exchanger. It pulls the extra heat from the combustion chamber and transfers it to the cooling system in the engine. Ensure that the piston has a proper heat range for heat to work effectively.

The operation principle of a spark plug

The ignition coil (magneto) generates high voltage when the car is turned on. This is where the spark plug is connected. The flow of electrons from the coil creates a voltage difference between the two electrodes (center and side).current flow in this case can only be prevented by insulators that is, the air inside the gap.

However, constant rise of the voltage changes the structure of the gases sitting between the electrodes. In the end, the dielectric strength of the gas is exceeded, ionizing it. Therefore, the ionized gas becomes a conductor and electric current can pass through easily. For this to work there must be a voltage in excess of 20,000 V for the plug to fire effectively.

The temperature of the spark channel within the electrons rises to 60,000K. Such temperature is enough to trigger a rapid expansion of the ionized gas. This expansion is what causes something like a small explosion that pushes the piston down.

If you observe a spark plug in action, you will realize it produces a click similar to that of a lightning and thunder. In the end, you have your engine working.

There is a reaction between the heat and the pressure force as a result of the explosion inside the cylinder head. There is a small ball of fire at the end of the of the spark plug resulting in the gases burning on them down.

The amount of composition mixture between the electrodes and the turbulence level differ in amount. For this reason, there are different sizes of the fireball. Small kernel usually has its effects on the engine. On the other hand, a large kernel will make the engine run like it received advanced timing.

Spark plugs may wear out with constant use. Sometime you will notice so much soot when you pull it out. In that case, it might not function properly unless it is cleaned or replaced.  

Types of spark plugs

There are several types of spark plugs available today. Here is a look into each type

Copper spark plugs

These types of spark plugs are most popular in every market. Hence you will not go extra miles in order to acquire them. They use a nickel coating as the electrode. The inner core alone is made of copper. Copper cannot be used alone since it melts under extreme heat hence the nickel is used to prevent this from happening.

The name ‘copper spark plug’ refers to the mode in which it has been structured they have inner coating made with copper.

These plugs are very advantageous. Copper is seen as the best metal when it comes to delivering the best spark. Under adverse conditions from turbo-chargers, the copper spark plug becomes the best tool for the job.  Most high end vehicle manufactures use copper/nickel spark plugs in the engines because of their efficiency.

The only downside is that they have a very short lifespan. But that is gapped by the low cost. You won’t even feel the pinch buying them from time to time.

Platinum spark plug

From the name, platinum spark plugs are constructed with a platinum center electrode. They are also referred to as single platinum spark plugs. They are the most expensive because platinum is not very easy to come by.

Platinum is harder that nickel. This is why they are very durable. Unlike other spark plugs,the gap at the end of the spark plug does not widen when the metal wears. That means, you will not start experiencing a drop in power any time soon.

Another advantage is that platinum plugs are more resistant to carbon build up. They are ideal to operate even in extreme conditions inside the ignition. Most modern engines require high power ignition system. The platinum is the most ideal compared to copper and nickel spark plugs.  

Double Platinum Spark Plugs

The single platinum spark plugs discussed have a platinum electrode at the center. The ‘double platinum’ spark plugs are a bit different. They feature platinum plating on both center and ground electrode.

They are more expensive compared to others but they yield slightly higher results in performance. They are more durable. They are slightly better than the single platinum once in terms of performance and durability.

Iridium Spark plugs

If you are looking for better power generally, then you should go for the iridium spark plugs. They offer a more complete combustion that makes the engine to run more smoothly. In essence, they also have a longer lifespan than the copper/nickel ones.

Iridium spark plugs can last nearly as long as those made from platinum. They are used in higher performing engines because of their ability to produce excellent power. The fine wire in them is able to conduct electrical energy more efficiently.

One down side of this particular type is that they come with the highest cost. They have greater benefits but their prices scare most people.

Silver spark plugs

These are spark plugs made from silver material. They offer the best thermal conductivity generally and are preferred excellent performance as well. But they are not as durable as the iridium or platinum ones. They are mostly found in the older European performance cars and some motorcycles.

Even though they are quite powerful in performance, they are not very popular perhaps because of how easy they are to wear out. They are quite fair in price as well.

How to gap spark plugs

The distance between the curved conducting electrode and the plug tip where the electricity comes from may require some adjustment. The process of adjusting this space is known as gapping.

It is done simply by bending the electrode itself. There is a special tool designed to help in this process. It is important to get the right gap distance. It will determine how much power output you get, the level of fuel consumption, the smoothness of your ride, and how long the spark plug will serve you.

The spark plug should not be too narrow. It will produce a small and weak spark that will fail to fully ignite the gas mixture. A gap that is too wide on the other hand may cause frequent misfires. Its important to choose  suitable applicable position that will not have any negative effects on both sides.

More expensive spark plugs come with a ‘fine wire’. This tool has been modified in such a way that it can  fit more premium metals around it to achieve better electrical conductivity. A special kind of tool is required for this design. Consider using a feeler gage tool. Otherwise, it is very easy to damage the tip or the electrode at the center, a case that will require you to incur extra costs of buying a new spark plug.

Gapping a spark plug is not as easy as it may sound. It is a very delicate operation since it needs the right amount of pressure at the tip where it is needed. If you made a mistake and pry against the center electrode, you may end up damaging the whole thing.

The heat range in spark plugs

Spark plugs work differently in different temperature ranges. In terms of thermal functionally, it is important for the device to achieve proper heat range. Too much temperature can heat up the spark plug and cause premature ignition. On the other hand, too cold spark plug may lead to carbon build-up with produces incomplete combustion.

The surface area of these plugs is large to sustain the heat from the combustion chamber. Hot plugs also have longer insulator nose. The firing tip gets hotter faster.

Cold plugs are designed with a short insulator tip. They are great at removing heat from the combustion chamber a lot faster. They don’t fire up with the cylinder temperature increases.

Choosing between cold and hot spark plugs is not easy. But you can use the factory specified spark plugs to drive in different conditions.


There is a great difference between a spark plug modified for great performance and others. If you are upgrading your car, consider plugs that are designed to withstand extreme lengths of mechanical shocks with little or no damage. You may think of a turbocharger but they are a variety of type and you have to choose the best.When you realize you have used the current spark plug for too long, it might be the best time to change it. We hope you now understand how to deal with such issues.

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