Note: Pre-90 normally aspirated and pre-91 turbocharged cars do not have the DI cassette.

Direct Ignition is an ignition system with no distributor and no ignition wires.  The DI cassette contains the entire ignition system and has no moving parts.  Four ignition coils built into the unit seat directly onto the spark plugs.  Signals from the crankshaft sensor tell the unit to fire the two cylinders that are approaching top dead center on each rotation.  The ECU senses which of the two cylinders is actually firing (by monitoring the "ionization current" across the spark plug electrodes) and controls the ignition timing as appropriate.