Importance of Heat Range
The heat rating is a measure of the amount of heat dissipation.The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type.
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Effect of Selecting Wrong Heat Range
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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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