Why have four wires to ignition coil?

Four wires to an ignition coil typically serve different functions: one wire is for the positive power supply, another for the negative ground, a third for triggering or controlling the coil (often from the engine control unit), and the fourth may be for feedback or signal return. This configuration allows for better control of the ignition timing and improves the performance of the ignition system. Additionally, it can help ensure reliable operation by providing a dedicated ground and signal pathways.