The engine spark plug, whether used in automotive applications or commercial and industrial use, serves a straightforward purpose. It has the job of sealing off the combustion chamber while generating a high voltage to spark an explosion of atomised fuel and air. Spark plugs come in many heat ranges, sizes and construction materials, which have reference numbers. Two Champion spark plugs, such as the RN9Y and the RN9YC, have similar designs except for an additional identification number.
Spark Plug Description, Letter "R"
The RN9Y Champion spark plug has four reference numbers that describe its specific application. The first letter, "R," describes the special suppressor shielding construction of the plug, which identifies it as a resistor-type plug, used for suppressing radio and engine-noise static. The RN9YC spark plug is no different in this respect.
The "N" describes the physical construction of the outer shell. In this case, the outer shell has a 14mm thread size, a 3/4-inch reach, or depth into the combustion chamber and a 13/16-inch hex bolt design. The RN9YC spark plug is the same as the RN9Y in this aspect.
Typically, Champion spark plugs that have numeral designations between 1 and 25 have application use in automotive and small engines only. The number "9" falls within this range, excluding it from use in larger commercial and industrial engines. The RN9Y and RN9YC spark plugs are identical in this respect.
In a Champion spark plug, the letter "Y" on the RN9Y spark plug refers to the firing-end design of the spark plug electrode. In this case, the "Y" indicates that this spark plug uses a standard projected core nose, one of the most common configurations. Electrode length determines the heat range, and in some cases, the depth of the plug inside the combustion chamber. The "Y" on the RN9YC spark plug means the same thing.
The extra "C" for the RN9YC spark plug identifies it as a copper-core plug, which makes the core construction material different from the RN9Y spark plug. The electrode centre contains an extruded copper core that promotes better heat-range distribution. This allows for longer plug life. The copper electrode element also resists corrosion and contamination better than the standard design. The RN9YC spark plugs have useful applications when used on HEI (high energy ignition) systems that require better quality and longer plug life.