[Henry Schmidt]

A little clarity in simple terms. Imformation from PRI tech reports.

Heat range: This is often dictated by the build of the engine, meaning that your build may require a colder or hotter plug than the factory specified. The heat range will dictate how fast the plug tip will dissipate heat from combustion. According to Brisk Racing and Performance Spark Plugs, a change of just one heat range impacts the tip temperature by between 75 and 100 degrees Celsius. With heat ranges, your goal is to keep the spark plug in the “self-cleaning zone.” This is the middle range of temperature—below the “self-ignition zone” (too hot, causing harmful self-ignition of fuels) and hot enough to stay above the “deposit zone,” which happens when a plug is too cold and then subsequently fouls because it is not hot enough to remain clean.





The top chart at left shows electrical conductivity, or how easily an electric current passes through metal. Silver is the best performing metal, meaning your ignition system would deliver more of its charge with silver than a lesser metal. The bottom chart at left shows thermal conductivity, or the rate at which heat passes through a material. Ideally, you want a metal that both conducts heat away fast and conducts current well. This means the spark plug would provide the best ignition and then conduct the residual tip heat out through the cylinder head quickly as well, for maximum performance and detonation resistance