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.
The ignition system sends an extremely high voltage to the spark plug in each cylinder when the piston is at the top of its compression stroke. The tip of each spark plug contains a gap that the voltage must jump across in order to reach ground. That is where the spark occurs. The voltage that is available to the spark plug is somewhere between 20,000 volts and 50,000 volts or better. The job of the ignition system is to produce that high voltage from a 12 volt source and get it to each cylinder in a specific order, at exactly the right time.