PLUG STUDIO / NGK

What is the heat rating of a spark plug?

A spark plug must dissipate the heat produced by the combustion gases. The heat rating is a measure of the amount of heat dissipation.

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The heat rating is expressed as a number.

· There is a greater surface area exposed to the hot combustion gases. · Heat transfer to the engine head is slower.		· Less surface area exposed to the hot combustion gases. · Heat transfer to the engine head is quicker.

Its firing end heats up quickly.		Its firing end does not heat up quickly.

It is essential to use a spark plug with a heat rating that matches a specific engine and its condition of use.

When a wrong heat rating is selected,
When the heat rating is too high,

The spark plug temperature remains too low and causes deposits to build up on the firing end; the deposits provide an electrical leakage path that gives rise to a reduction of spark.

When the heat rating is too low,

The spark plug temperature rises too high and induces abnormal combustion (pre-ignition); this leads to melting of the spark plug electrode that could cause problems such as piston seizure.

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