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Iridium Spark Plug



Ignition performance of ultra-fine electrodes

The reason for improved acceleration and fuel economy. Ignition performance of the ultra-fine electrode.
Concentrated spark Accelerating flame
Watch the ignition characteristics of an Iridium Plug
point"Ease of spark formation" + "ease of growth of the flame nucleus" = ignition performance
Quenching action has a major effect on ignition performancem
At this stage, due to the quenching action of the center electrode and ground electrode there is a danger that the flame core will be extinguished and ignition will fail. Minimizing this quenching action and making the flame core grow as fast and as big as possible are key to improving ignition performance.
photo Quenting action of the electrodes
The action of the electrodes, which are at a low temperature, in absorbing the energy for growth of the flame core immediately after the spark is formed is called the quenching action.
·Why are the ignition characteristics of the Iridium IX plug so good?
The center electrode has a small diameter and the tip of the ground electrode is cut to give a tapered form, and this is what produces the excellent ignition characteristics.
The quenching (cooling) action of the electrodes is small.
Iridium IX plug photophoto Because the tip of the electrode has been given a small surface area, the Iridium IX plug has a small quenching (cooling) action and the flame can grow extensively.
The electrodes have a small surface area and the amount of heat absorbed is small.
Nickel type plug photophoto When the plug electrode temperature is low (when starting the engine, when idling, at low speeds, etc.), if the area (volume) of the electrodes is large, as it is in a Nickel type plug, energy is absorbed due to the low electrode temperature and growth of the flame is impeded.
Heat is absorbed by both the center electrode and the ground electrode
Iridium IX plug photophoto On an Iridium IX plug the tip of the electrode forms a sharp angle so there is little dispersion in the position where discharge occurs and discharges are concentrated at the tip. This means that the flame grows quickly without being impeded and the ignition performance is improved.
Discharge occurs at the tip of the electrode so there is little dispersion.
Nickel type plug photophoto In the case of a Nickel type plug, the discharge position is liable to dispersion. For example, if discharge takes place at position (1) as indicated in the photograph to the left, the ground electrode impedes the growth of the flame and combustion becomes unstable.
Discharge occurs at a position where it is difficult for the flame to grow.

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