Copper core ignition leads with interference suppression are comprised of a copper core. A silicone layer surrounds the core, which serves as an electrical insulator. Copper is an excellent conductor, but is also very sensitive to corrosion. Therefore, the copper core of such ignition cables is tin-plated. The outer insulation, made of silicone rubber, can withstand temperatures up to 220°C and is resistant to gas and oil.
Carbon resistor ignition leads are comprised of a fiberglass core with a silicone interior insulation. There is a coal-impregnated braided fiberglass inside a carbon resistor ignition cable. For carbon resistor ignition cables, the interference suppression resistance depends on the wire length. You can calculate this on NGK SPARK PLUG's TekniWiki website.
Two silicone layers and fiberglass fabric surround ignition leads with inductive resistors. Like carbon resistor ignition leads, these ignition cables have a fiberglass core. The inner insulation made of silicone provides for stability and protects against high ignition voltages. You can calculate the interference suppression resistance on NGK SPARK PLUG's TekniWiki website.