Spark Plugs: Heat Rating and heat Flow Path
Heat rating and heat flow path of spark plugs
The distance from the point where the metal shell and the insulator meets to the firing tip of the insulator is termed as Insulator Nose Length. The tip temperature is a primary and significant factor in pre-ignition and fouling, since the insulator tip is considered to be the hottest part of the spark plug. The temperature of the spark plug tip should range between 500°C and 850°C independent of the vehicle it is used, let the spark plug be used in a street car, a race car, a speed boat or even a lawnmower. The temperature of the insulator area around the center electrode will not be hot enough to burn off the combustion chamber deposits and the carbon deposits, if the temperature of the tip of the spark plug is lower than 500°C. The deposits of carbon and the combustion chamber deposits can make the car misfire due to spark plug fouling. Conversely, if the tip temperature of the spark plug is greater than 850°C, it will overheat the spark plug and the ceramic around the center electrode might blister thus by melting the electrodes. This may cause detonation / pre-ignition and may lead to severe engine damage which is expensive. In identical types of spark plugs, the difference from one heat range to the next is the ability to remove around 70°C to 100°C from the combustion chamber. While in a projected style spark plug, the temperature of the firing tip is increased by 10°C to 20°C.
