Double-Ignition System
Two spark plugs per cylinder ignite air/fuel mixture. With this system, burn time of air/fuel mixture is shorter because of shorter spark travel. Detonation is also less likely, making it possible to increase compression ratio and improve thermodynamic efficiency in engine. Ignition must be triggered about 6 degrees later because of shorter spark travel and burn time. Ignition triggering signal goes from DME control unit to 2 ignition control units installed on left side in engine compartment.
In each ignition final stage, a transistor is activated, which interrupts secondary circuit of both ignition coils (also installed on left side of engine compartment). In this manner, an ignition spark is created by both ignition coils for each cylinder in sequence. A Hall Effect sensor, installed in double-ignition distributor, identifies cylinder No. 1 (ignition TDC). See Fig 1 . Hall signal is required by DME control unit for assignment of both knock sensor signals, as well as for sequential fuel injection control.
Each distributor rotor is controlled by centrifugal weights. This ensures alignment between distributor rotor and corresponding ignition contact in distributor cover.