Traditional coils (oil filled/wet coils/can type). The oil-filled ignition coil is also called open magnetic circuit type ignition coils. In conventional ignition system, oil filled ignition coil was used widely, and also applied in the electronic ignition system later which structure is the same as the ignition coil used in the conventional ignition system. Ignition coil has two coils of wire, the primary coil and the secondary coil. Primary coil with thicker enameled wire, usually around 0.5-1 mm enameled wire around 200-500 turns.