Distributor: Description and Operation

Double Ignition










The distributor is actually two distributors built into one.
A hall sender which is required for identification of cylinder number #1 (ignition TDC) is installed in the double ignition distributor. The hall signal is required in the DME control unit for assignment of both knock sensor signals as well of control of sequential fuel injection.
Each distributor rotor is guided by centrifugal weights depending on engine speed. This guarantees alignment between the distributor rotor and corresponding ignition contact in the distributor cover
911 Carrera has two spark plugs for each cylinder to ignite the air/fuel mixture. In this manner, the burning through time of the air/fuel mixture is shorter because of shorter spark travel and there is also less tendency of knocking, through which it is possible to increase the compression ratio and therefore improve the thermodynanic efficiency of the engine. Ignition must be triggered off about 6° later because of the shorter spark travel and burning time