These units detect crank speed and throttle position in order to determine the exact requirements for ignition timing in any given situation. Crank speed is typically measured either from teeth on a specially produced crank pulley (see right), or from teeth cut into the back of the flywheel.

The ignition system includes a twin coil for distributorless wasted spark ignition. This delivers much greater spark energy and replaces potential points of mechanical failure in the original system.

As well as it's primary function to control ignition timing the ECU also has outputs for a tacho drive, fuel pump relay, and auxiliary relay (typically used to control an engine bay fan). The package comes complete with an engine bay wiring loom which also includes a gearshift warning light.

These packages are supplied pre-programmed but also include software and a manual allowing complete access to all ECU settings.