What does a CDI box do?

A CDI, or Capacitor Discharged Ignition is a system that is linked to the ignition of some petrol engine driven vehicles. Its purpose is to store an electrical charge that is discharged through the ignition coil and thus increases the power to the spark plug/s for a very powerful, high-energy spark. This prevents fouling of the spark plug/s. A CDI can be disconnected in some vehicles and the engine would still run, but with a less powerful spark to the spark plug/s.