Spark plugs are an element that can be found within internal combustion engines. These types of engines need a spark so that the mixture of air and fuel can start the combustion process. They are also in charge of absorbing the heat generated in the engine chamber and dissipating it towards the car’s cooling system so that it can work at its appropriate temperatures.


Spark plug parts
These have different parts, some of which are essential for its operation, such as the resistance, the electrode, terminal, etc. Other parts belong to the housing that serves for the protection of the main components and also for mounting on the motor:

High Voltage Terminal: Used to connect a wire to drive the spark plug
Ceramic insulator: Insulates the electrode from high temperatures.
Thread: Used to insert the spark plug into the engine.
Central electrode: Usually connected to an internal conductor and a series of ceramic resistors to reduce spark noise.
Metal casing: It serves to dissipate the heat of the insulator, it also works as ground and is attached to the side electrode to complete the circuit of the electrodes.
Side or ground electrode: This electrode is attached to the housing that acts as the ground so that the circuit is closed and electricity passes between the central electrode and the ground electrode and thus the spark can be generated.
Corrugated or ribs: They serve to prevent electrical leaks, their corrugated shape generates greater resistance and thus prevents electricity from leaking from the high voltage terminal (central electrode) towards the casing.

Spark plug classification and types
There are two ways to classify them all depends on their thermal degree, either the high-grade ones that are capable of transmitting heat faster, better known as cold plugs, or the low-grade ones that transmit heat more slowly, to these they are known as hot plugs. There is a simple way to identify what class it is, if the insulating material on the electrode is small it is a cold one, otherwise, if it is long it is a hot one.

We can also find different classifications and types of spark plugs, such as their resistance, according to the size of their electric arc, by the type of fuel, by the number of electrodes, with a laser system, with or without a bridge, by their type of material and by the neck of the thread.

Classification by resistance
These spark plugs are present indirect injection diesel engines and are used for pre-heating.

Bare resistance
They are one of the first to be used and, as the name implies, the resistance is exposed.

bare resistance spark plug

Protected resistance
It is used to preheat the motor but in this type the resistance is protected with a cover to transmit heat more quickly and effectively.

Resistance Protected resistance

Antiparasitic resistance
It is a variation of the spark plug with protected resistance, only that inside it has a resistance that helps to eliminate the interferences that may exist in the electrical system.

Anti-interference spark plug

By the size of the arch
They are classified by the distance that the spark must travel between the central and lateral electrodes.

Normal opening
It is the most common in current engines, the bow jumps up to 9mm.

Large opening
This type requires high voltage coils in the ignition system since the spark reaches up to 2.5mm.

Spark plug gap

By fuel type
We can find spark plugs for different types of fuels, be it gas, gasoline or diesel.

Spark plug
They work with a high ignition voltage because the mixture of air and gas is more stable than that of a conventional gasoline engine. Its coating is nickel to improve temperature support and prevent gas corrosion from rapidly wearing down the electrodes.

Spark plug

Spark plug for gasoline
They are the most common because gasoline cars are the most used, they have the characteristics of bare spark plugs.

Gasoline spark plug

Diesel spark plug
These are incandescent or pre-heating, these spark plugs heat the air and are capable of achieving temperatures of up to 1000ºC so that the self-ignition of diesel engines that do not have direct injection can work even in cold weather.

Spark plug for diesel

By number of electrodes
Within this type we can find spark plugs with 2 or up to 4 electrodes. The multi-electrodes serve for a more balanced ignition, since they alternate, thus increasing their useful life in a way directly proportional to the number of electrodes equipped.

Multi-electrode spark plug

With laser system
These are relatively new and conventional spark plugs are replaced by lasers that point directly to the exact center of the fuel-air mixture to optimize combustion.

With or without a bridge
This is a component that can be attached to cold spark plugs, it is a detector capable of diverting the cooler air that enters from the crankcase so that it does not turn off or cool the filaments of the spark plug.

Spark plug bridge

Due to its type of material
These components are made of different types of materials, depending on the type used, it can improve performance.

They are the most common because they conduct electricity better.

copper spark plug

Platinum or iridium
Their cost is higher but their duration is also longer, this is because they have less conductivity. To solve this problem, they have a central electrode that compensates for the jump in the current.

Platinum spark plug

By the neck of the thread
When a spark plug is installed, it must always be flush with the surface itself, since if there is a surplus or missing thread it can make it difficult to change the next spark plug, since it would fill with carbon or carbon.

Tapered seat
These do not require gaskets as they seal tightly when screwing.

Spark plug conical seat
The thread length is shorter and they are used for thin motorheads.