About the spark plugs

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In this article I talk a little about what spark plugs are, how they work inside the engine, types and some problems associated with them.

Hello, everyone, this time I am going to talk about the spark plugs which are one of the most important elements of the engine. The truth is that I was searching the internet and there is a lot of talk about them, but the information is very scattered and that is why I decided to write about it.

What are the Spark Plugs?

motor 4 tiempos funcionando As it is well known inside the engine cylinder air and fuel are mixed and then compressed, then this mixture needs heat to finish igniting. This additional heat is given by the spark that is given in the spark plug. I mention the end of igniting "the mixture", it is because in the process of violent compression it produces a lot of heat, but in an Otto cycle engine not enough to turn it on.

In the image you can see the moment when the spark starts the explosion inside the cylinder that lowers the python.

Types of spark plugs for engines

According to its thermal degree

Spark plugs: those that have the tip of the insulator very long, and the heat path is not direct, so it evacuates little heat from the combustion chamber to the cylinder head. Hot spark plugs conduct heat slowly and stay hot longer. The car that only makes short trips in the city, needs hotter spark plugs to burn the coal deposits.

Cold spark plugs: those that have the tip of the insulator cuts, and the heat path is very direct, so it evacuates a lot of heat from the combustion chamber to the cylinder head. Cold spark plugs conduct heat quickly and stay cool.

grado termico de las bujias

Already spoken of this it is important not to be confused with the terms of cold or hot. That is, the spark plug is not cold or hot because of the temperature reached by the combustion or because the spark is of a higher temperature, but rather because of the heat it transmits to the cylinder head.

The factors that determine the thermal degree are the compression ratio, the type of admission (atmospheric or supercharged) or the operating conditions of the engine.

According to the number of electrodes

Depending on the service conditions and the application, various forms and different materials are used for the electrodes.

Numero de electrodos de las bujias

In the spark plugs of 2, 3 and 4 electrodes, the spark jumps in the electrode that is cleaner at that moment, and therefore the wear of the same varies from one to another (and in different place of them), this produces a longer spark plug life (2/3 or 4 electrodes have to be spent to fail). It does not have another difference with the common spark plugs of a single mass electrode.

  There is no need to calibrate them because as the electrodes wear out, the spark jumps to the nearest electrode.

Another important thing to say is that the spark does not jump for all the ELECTRODES at the same time, only for the one that has the best conditions for the moment, a very deep-rooted myth among people.

desgaste de bujias animado

The increase in the number of electrodes in the spark plug was not made in order to improve the performance of the spark as such but rather to extend the service life of the spark plug. So in my particular opinion a new spark plug of a single electrode will not make any difference to another spark plug of two or more.

According to the construction material and quantity of the electrodes

The electrode is another feature that differentiates the models of spark plugs that can be used in a vehicle.

The wear of the electrodes is due to erosion (abrasion by ignition sparks) and corrosion (chemical-thermal attacks). The charred remains of air and gasoline from the explosions are deposited in the electrodes, this causes the spark to lose intensity and temperature progressively resulting in poor combustion, lower gasoline performance and greater contamination.

bujia de platino o de iridio

Something very important in the spark plugs are the metals with which the electrodes are built, which has to do with the duration of the same. The nickel plugs were the first, then copper plugs appeared, after platinum, double platinum, iridium and double iridium. Generally speaking, the nickel plugs last about 30,000 km while the double iridium spark plugs can last up to 150,000 km. The difference between these metals is the conduction capacity of electricity and its resistance to wear. Platinum and iridium are precious metals and therefore spark plugs are more expensive.

According to the separation between electrodes

The separation between electrodes (SEP) is the shortest distance between the central electrode and the ground electrode. The smaller the spacing between electrodes, the less the ignition voltage will need.

separacion electrodos en bujias

In the case of too small an electrode spacing, the ignition voltage will certainly be small, but misfiring can occur, because insufficient heat energy is transmitted to the mixture due to the short spark.

Too large an electrode gap requires a high ignition voltage for the coil that can overheat it and shorten its life. Thus, the energy is transmitted very favorably to the mixture. However, you have to be sure that the installed coil can support this operation.

The separation between electrodes is prescribed by the manufacturer depending on the make and model of the vehicle.

It's all for the moment, I also have another interesting article of some recommendations to follow when we change the spark plugs, you can see the article in this link.

Well it's all for now, I hope you like it! Greetings.

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Written by:

Dennis García

Mechanical Girl




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    About the spark plugs

    About the spark plugs

    In this article I talk a little about what spark plugs are, how they work inside the engine, types and some problems associated with them.

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