What Spark Plugs Do and How They Work

Spark plugs are small electrical devices used in some internal combustion engines and are prevalent in the function of your vehicle's engine. They feature an insulated electrode in the center, insulated wire, and an ignition coil or magneto circuit with a grounded terminal. All of these components work together to form a spark gap. However, while that might explain what a spark plug is, it does not answer the question, "What do spark plugs do?" Or, even why these small, fragile elements are essential to the operation and functionality of your car?

While you can get familiar with the consequences of a faulty spark plug pretty quick, the number of average motorists who can explain the purpose and operation of these devices are likely few, which is unfortunate. The fact is, spark plugs hold the power to ignite your engine. Without them, your vehicle would be an enormous and awkward paperweight. Therefore, to ensure that you understand the importance of these hold-in-the-palm-of-your-hand devices, we have put together this little guide, which will explain the function and operation of spark plugs as well as common materials and other pertinent information about their use.

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What Do Spark Plugs Do?

The fundamental function of a spark plug is to aid in the combustion process of your engine. Basically, the plug fits into your car engine’s cylinder head and is connected to the ignition coil. The ignition coil then generates the high voltage needed to create the spark from the plug. When the spark occurs, the fuel ignites, allowing your engine to run. However, if the plug is damaged, then there is no spark to ignite the fuel and your vehicle’s engine will not run. Therefore, while it is small and fragile, the spark plug is one of the most critical elements in a car.

How Does a Spark Plug Work

The ignition process of your vehicle does not begin with a spark plug. Actually, the process starts at the gas tank. Essentially, the fuel pump moves the gasoline from the tank to the fuel injectors. Then, as the fuel reaches the throttle body, the engine’s air intake system sucks oxygen into the cylinders. The fuel and air are mixed, forming a highly combustible relationship, and injected into the cylinders, where the ignition coil releases the appropriate voltage to create a spark from the plug, which ignites a small explosion in the spark channel to power the engine. This process occurs at a rapid rate, typically thousands of times per minute, and the spark plug is the backbone.

What Type of Spark Plugs Do I Need?

There is a lot of debate about the power differences between different spark plug electrode materials. All of the discussion is mostly nonsense. The best judge of which spark plug is best is your vehicle manufacturer. Therefore, when in need of a spark plug replacement, trust your owner’s manual above all else. However, that being said, there are several differences between the top three spark plug materials: copper, iridium alloy and platinum.

1. Copper

Copper electrodes are among the most popular and find the most use in combustion engines. They are stronger conductors than iridium and platinum, and they are often used in high-performance or modified engines. However, these plugs do not last as long as the other two metals, typically wearing down or needing replacement about every 20,000 miles. Despite their shorter lifespan, these plugs are among the cheapest to replace.

2. Iridium alloy

If you are willing to spend a few extra bucks, then you might consider iridium allow spark plugs. While these options do not have the highest conductivity level, they do last nearly twice as long, 40,000 miles, as copper plugs. It is necessary to note that these plugs are not recommended for modified engines.

3. Platinum

Platinum spark plugs are not recommended for every engine. However, they are known for having superior resistance to time-borne corrosion, and they have a similar life expectancy to iridium alloy. Although, these plugs are typically recommended for only newer vehicles with electronic ignition systems that are distributor-based or even DIS systems.

Again, while there are a few varieties of spark plugs available, they will not all be right for your particular vehicle’s engine. Therefore, before going out and buying a replacement plug, review the recommendations from your vehicle manufacturer found in your owner’s manual.

What Heat Range Spark Plug Should I Use

The discussion of spark plug heat ranges is typically only necessary for vehicle manufacturers and those savvy car owners who have modified their vehicles for performance increases. For those drivers, it is necessary to understand the different ranges and which range is right for your car.

There is a common misconception that spark plugs generate heat, but this is not true. In fact, the entire point of the design of the plug is to channel heat away from the tip, which is where the length of the insulator mass comes into play. Essentially, the way that heat range works is determined by the length of the insulator. For example, shorter insulator masses have a cooler heat range than longer ones. For proper function, the tip of the plug must remain cool enough to prevent preignition but hot enough to maintain self-cleaning.

When deciding on a proper heat range and plug, you need to understand how hot your car’s fuel burns. This is a measurement that is impossible to change, regardless of modifications. Therefore, it is typically recommended to stick to the factory recommendations when it comes to choosing spark plugs.

What is the Spark Plug Gap?

For optimum engine performance, it is not enough to select the appropriate plug and heat range. You must also set the gap to the precise distance. Again, you can review your vehicle’s manual to determine the proper gap, and you can use tools specifically designed to set the plug gap.

While most vehicle owners don’t think twice about their vehicle’s spark plugs until something goes wrong, you now know the answer to the question, “how does a spark plug work?” Therefore, with your newfound knowledge, the next time you hear your engine knocking or struggling to ignite, you will know why, and you can then go out and buy the correct plug for your car.

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