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Show CTTcrence Between Hot and Cold Spark Plugs F'Kirk plugs may be .lust plain plugs n-'d :'ll alike to the motorist at present, pres-ent, hut when airplanes become coin picnnliK-p all this may 'ie changed. I'nr Instance, there Is a change In 1'iaik plug design. Indirectly traceable in aviation at least, which brings the r-ool plug into motor car use whereas previously only hot plugs were phi-ph". phi-ph". ed. At that, the cool plug In motor car engines Is not so cool as i but In aircraft power plants. What Is the difference? A hot plug Is one so designed that it becomes sufS:'ontly heated to burn off the ac-euiM;lailon ac-euiM;lailon of oil and gasoline that might produce carbon, thus short-circuiting short-circuiting the Insulation. A cool plug is Just the opposite. Higher compression compres-sion Is bringing the latter type into the foreground. |