If you’re like me, you probably spent your whole life thinking about spark plug choices only in terms of the materials they’re made of. You know, like how most cars use copper spark plugs, but you can pay for better ones made out of platinum or iridium. For most people, choosing the correct spark plugs is only a matter of choosing from one of those three options.
For some car owners, however, there’s also the concern of heat range. You see, spark plugs can also be categorised on a spectrum of whether they’re hot or cold spark plugs.
Confused? Don’t worry, because you’ve come to the right place to learn everything there is to know about spark plugs. Firstly, if you’re interested in learning about spark plug basics, check out this article.
In this article, however, we’re going to discuss the topic of spark plug heat ranges and whether a hot spark plug or cold one would be better suited for your vehicle.
What Is a Spark Plug Heat Range All About?
Let’s start with the basics of spark plug heat ranges. Simply put, some spark plugs operate at a much higher temperature than others. All of it depends on how much surface area of its porcelain is exposed.
A ‘hotter’ spark plug has a longer insulator nose. In other words, more porcelain surface area is exposed, enabling it to absorb more heat. This type of spark plug heats up much faster, but more importantly, it doesn’t let much of that heat dissipate or transfer to the cylinder head.
A ‘colder’ spark plug with a shorter insulator nose, on the other hand, is the complete opposite. It has less of an exposed porcelain surface area which means that it runs cooler. Any heat that it absorbs dissipates very quickly as it transfers over to the cylinder much more efficiently.
But remember: we’re talking about a heat range (emphasis on the word ‘range’). That means spark plugs don’t just fall into the category of hot or cold. Instead, there are spark plugs that are ‘hotter’ or ‘colder’ than others along the heat range or spectrum.
When Should You Use a Hot Spark Plug?
You may not realise it, but the odds are high that you probably have hot spark plugs inside your car right now. That’s because hot spark plugs are best suited for light-duty vehicles whose engines aren’t particularly high-performance.
The engines in regular light-duty vehicles aren’t exceptionally high in compression. As a result, the spark plugs don’t experience much turbulence going on inside the combustion chambers.
When Should You Use a Cold Spark Plug?
Spark plugs further towards the colder end of the heat range are best suited for high-performance and heavy-duty vehicles, thanks to their shorter insulator nose. That’s because those cars have high-compression engines with lots of turbulence going on inside the combustion chambers.
Therefore, colder spark plugs with shorter insulator noses are somewhat protected from that compression and turbulence. Better yet, these kinds of spark plugs don’t retain much heat, transferring most of it to the engine head much more effectively.
What Happens If You Use the Wrong Heat Range for Your Engine?
Like most components inside your car, spark plugs can only work correctly when they’re at the optimal temperature, not too cold and not too hot. So, what happens if you use the wrong type of spark plug for your vehicle?
What Happens If the Heat Rating Is Too Low?
Spark plugs can function perfectly well inside the hot environment of a combustion chamber. However, if your spark plug’s heat rating is too low for your engine, that plug will become far too hot.
As you might have guessed, a spark plug that gets too hot will overheat. To be more specific, the electrode on a spark plug will overheat to the point that it glows brightly.
With prolonged overheating, the spark plug itself may end up melting. That could lead to uncontrolled or abnormal combustion as a result of what is called pre-ignition.
Taken a step further, you may end up with nightmare scenarios involving piston seizure and severe engine damage.
What Happens If the Heat Rating Is Too High?
On the other hand, if the heat rating is too high for your car, it means that the spark plug will be too cold and never get a chance to reach its optimal temperature.
A spark plug that fails to heat up is bad news, albeit a different kind of bad news.
You see, when a spark plug heats up correctly, it can reach what’s called the ‘self-cleaning temperature’. At that temperature, there’s enough heat to burn off any carbon and prevent it from building up around the spark plug.
Conversely, a spark plug that’s too cold will not be able to do that, leading to carbon particles building up on the spark plug and forming deposits, or ‘carbon fouling’. That’s terrible news for a spark plug because the buildup will prevent it from creating the spark needed for an efficient combustion process in the combustion chamber.
Instead, the ignition voltage will flow to the ground rather than create a spark at the plug’s gap, leading to an engine misfire.
How Do I Choose the Perfect Spark Plug Heat Range?
Suppose you’re driving a regular car straight from the dealer, and you’ve never made any modifications to your engine. If that’s the case, then perhaps the spark plug heat range is not something you need to worry about.
Your trusted mechanic will recommend a standard spark plug that works well for the kind of engine you’re using. And, of course, your car’s user manual will specify the ideal type of spark plug for your engine type.
However, you might want to start shopping for a spark plug on the colder end of the heat range if you:
- Have supercharged or turbocharged your engine.
- Use nitrous oxide or methanol.
- Have modified the air/fuel mixture or ignition timing for your engine.
- Drive at high speeds for extended periods, such as when racing.
To shop around for colder heat range spark plugs, please check out Carpart.com.au. You may submit a part request to find suppliers who have what you need, or browse the marketplace to find great deals on new and used car parts! Try CarpartAU now!
By Ray Hasbollah