These ignitions did just fine for decades, but those moving parts wear out over time. Springs, weights, cam lobes, and other simple machines worked together to deliver spark at the right time, even as revs rose. Andy Greaser photo.ĬDI's complexity is in its circuitry, but its ancestors relied on clever mechanical systems to fire the coils.

On an electrical engineering level, it's different from CDI, but the troubleshooting process is the same. For the purposes of this article, I'll refer to all the black box ignitions as CDI, since they all use the same basic components: box, coils, sensor. In addition to dischargin’ those capacitors, the box may also influence your rev limit, timing advance, and other variables related to spark, but that’s it.Ī popular variation of this system is TCI, which doesn't use capacitors in the same way. The trigger tells the box to fire, the box determines when to fire which coil with the capacitors, and zap goes the spark plug, ad infinitum.

The basic CDI system is a trigger mechanism, coils, and a box, often black, with capacitors and other circuitry inside. You'll often find them lurking under your seat. What sets them apart is their ability to release all that energy near instantaneously, which is ideal for an ignition circuit.

Let's take a look inside.ĬDI stands for capacitor discharge ignition (alternatively, “capacitive.”) If you’re new to capacitors, they’re similar to batteries in that they can store energy for later. If you're not, you're wondering what a CDI does. If you're lucky, you're reading this for your own education. Black box, brain box, pulse pack, igniter box, CDI module, power pack, whatever you want to call it: if your motorcycle is newer than 1980, it probably has a black rectangle spouting wires under the seat that makes the magic happen.

Cycle sounds magic box