The most important parts of a spark plug: 1 and 2 - threaded contact nut, 3 - ceramic insulator with ribs to prevent leakage currents, 4 - contact rod, 5 - compression and heat shrinkage zone, 6 - sealing ring, 7 - spark plug body, 8 - insulator thermal cone, 9 - middle electrode, 10 - side electrode.
Slight wear after 90 thousand km: New nickel-yttrium alloy (up) lasts noticeably better than regular nickel (at the bottom)
Heat number
For accurate operation of the spark plug, immediately after starting the engine, it must heat up to a self-cleaning temperature, which is approximately 400 degrees, otherwise combustion products will settle on the thermal cone of the insulator. At full load, the temperature should not exceed about 800 degrees. Of course, the conditions under which spark plugs operate in different engines are not the same. It is possible to determine whether spark plugs and a particular engine are suitable for each other only on the basis of the glow number. If, for example, you use spark plugs with too high a glow number, then the thermal cone of the insulator can become very hot. This can lead to uncontrolled glow plugs that can even destroy the engine. If, on the other hand, you choose plugs with a too low glow value, the plugs will not reach their self-cleaning temperature and the thermal cone of the insulator will become dirty. The glow number is set by the car manufacturer.
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