Spark Plug Construction: DENSO Iridium

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Spark Plug Construction

Only the BEST

DENSO Iridium Spark Plugs use the highest quality materials, and are produced in our state of the art manufacturing facilities.

Below is a cross-section of the highlights of the Iridium plug. Click on any of the yellow circles for a detailed explanation.

Insulator	Copper-Cored Center Electrode	Tapered Cut
Five-Rib Design	U-Groove Ground Electrode	360° Laser Welding
Copper-Glass Seal	Patented Iridium Center Electrode	100% Pre-Fired

Ultra Fine Electrode

By harnessing the power of Iridium, DENSO is suddenly able to shrink the surface area of the center electrode - the critical component of a spark plug. Unlike a typical platinum plug that has a 1.1mm diameter center electrode, DENSO Iridium Power plugs have the world's smallest center electrode measuring 0.4mm in diameter. This means that the voltage requirements are decreased while firing performance is greatly improved.

U-Groove Technology

Our patented U-Groove design changed the industry standard in the mid 1970s by providing a better design that virtually eliminates erratic starts caused by poor fuel mixture. The U-Groove results in less flame dissipation making the spread of the flame nucleus easier and therefore yielding greater firing energy. It gives the flame a groove to grow in, thereby creating a larger flame front for a complete combustion.

On a conventional plug, the flat electrode design crushes the spark, and the overall volume of the flash front is smaller.

The conventional method to improve firing was to increase the spark gap. This has a negative effect on the spark. With a U-Groove firing can be greatly improved without increasing the spark gap.

Tapered Cut

To help improve ignitability DENSO minimized the portion of the ground electrode that comes in contact with the flame nucleus. Because the area of the ground electrode where the tapered cut comes into contact with the flame nucleus is small, the heat lost to the electrode is lessened and firing performance improves dramatically. The surface area and weight of the ground electrode tip is reduced along with the load in terms of heat and vibrations. This means the spark plug can cope with heavier driving conditions.

SAE Comparison of electrode sizes and voltage requirements


Iridium Plug (Ø 0.4)	Iridium Plug (Ø 0.7)


Platinum Plug (Ø 1.1)	Nickel Plug (Ø 2.5)

The figure on the above contains photographs of the discharge part of an ordinary spark plug, a platinum spark plug and the two types of iridium spark plugs developed here.

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