Local color. local color-The true color of an object or a surface as seen in typical daylight, rather than its color as seen through atmosphere or interpreted by the taste or imagination of the artist. Thus the characteristic local color of a lemon is yellow.
A spark plugs reach is calculated by the length of the threads. It is measured from the seat of the plug to the end of the threads. It should be noted that the reach does not include the electrodes, or an extended metal shell. When custom-selecting a spark plug, the electrode length and projection should be included in the calculation when taking into consideration the clearance in the combustion chamber.
Spark plug heat dispersal. The heat that the electrode section of the spark plug receives due to combustion is dispersed through the path in the figure. The degree to which a spark plug disperses the heat it receives is called its heat range. Spark plugs with a high degree of heat dispersal are called high heat range (cold type) and those with a low degree of heat dispersal are called low heat range (hot type). This is largely determined by the temperature of the gas inside the combustion chamber and the spark plug design.