Types and classification of spark plugs

For an internal combustion engine to work, it needs an element that provides the spark necessary for the fuel to ignite in the combustion chamber and start the process. This item is the plugs, but let this name not mislead us, because of the evolution and the different types of engines that exist today there are plenty of spark plugs.

In addition, spark plugs not only provide this spark, but they are also in charge of divert the heat that is generated in the combustion chamber internal to the engine cooling system. For this reason, we have put together a brief guide on the types of spark plugs that exist and how they are classified.

Spark plug classification

The main element by which we can classify them is their thermal degree. That is why we have spark plugs of high thermal grade (transmit heat faster) known as cold plugs, or on the contrary low heat spark plugs (they transmit heat more slowly), these are known as hot plugs.

La thermal degree measurement is set by the manufacturers, using a specific scale obtained by laboratory tests, measuring the maximum time a spark plug works when exposed to excessive heat, until it self-ignites. The scales result in a number between 45, for the hottest plug, and 500 for the coldest.

inside of an engine
Related article:
Self-ignition, detonation and connecting rod knock

types of spark plugs

However, in addition to this classification system there are also others, among which are these.

according to its resistance

This type of spark plugs are present in indirect injection diesel engines.

  • Bare resistor spark plug. They are the ones of a lifetime and in them the electrical resistance is exposed (it can be seen with the naked eye).
  • Shielded resistor spark plug. The electrical resistance is covered with a magnesium oxide sheath to transmit heat more quickly and effectively.
  • Antiparasitic resistance spark plug. This type is a variation of the previous one, because inside its magnesium oxide chamber it has a resistance that helps to eliminate any interference that may exist with the car's electrical system.

Depending on the size of the arc current

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For the arc current size. Distance that the spark has to travel from the central electrode to the lateral one. This spark can be reduced if the side electrode is damaged.

  • Normal gap plugs. The arc current jumps up to 0,9 millimeters. It is the simplest of all and the most common in current engines.
  • Large aperture spark plugs. In them the current arc can be up to 2,05 millimeters and to work properly they need high voltage coils in the ignition system.

By type of material

Depending on the material from which the spark plugs are made, they can be of one type or another.

  • Platinum or iridium spark plugs. They are the most resistant because they have less conductivity, which they compensate for with a pointed central electrode that facilitates the jump of current. Its price is higher than the traditional copper ones.
  • copper spark plugs. The best known and most conductive.

By number of electrodes

The number of electrodes can go from one to four or five. The difference between a multielectrode and one with only one lies in its durability. The reason for this is that in those that have several electrodes, the work is divided when the electricity has to be transferred and therefore it suffers less.

In those that there is only one electrode, the work is carried out through a single path and therefore it is the one that suffers all the work, significantly reducing its useful life.

By type of fuel

Finally, even though there are more classifications, we have the spark plugs by fuel type.

  • spark plugs for gasoline. They are the best known and most common, as they have the characteristics of bare spark plugs.
  • spark plugs for engines Diesel. The shape of this element varies considerably, since it is an incandescent tube that is located in the butt and sends the heat directly to the internal combustion chamber. To produce the ignition of the mixture in the engine, it can reach more than 1000º centigrade. They tend to be delicate at low temperatures, as they need more time to reach the necessary temperature to work.
  • Spark plugs for engines gas. Like for example those of Liquefied petroleum gas (LPG) and Natural Compressed Gas (CNG). The main problem with this type of spark plug is the wear of its electrodes due to oxidation, which is why they are usually nickel-coated to eliminate the inconvenience. In them the ignition voltage is higher to enable the combustion of the gas and air mixture.

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      pakito said

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      i am tro y same bruno said

    Very interesting, now I know which one is best for my car.

      louis vasquez said

    What type and number of spark plugs does the Fiat Uno Fire 2007 use? I appreciate who can help me

      Jorge Cardona said

    friend I have a keeway 250 motorcycle but it burns the spark plugs they last very little it is air cooled what spark plugs should I use I will appreciate your help

      gilberto porras said

    what is the diameter of the spark plug used by the skoda car model 1995

      Felipe said

    Hello friend, I read the article on spark plugs, I wanted to ask if you can explain the difference between iridium spark plugs and double iridium spark plugs.
    thanks greetings