911 Turbo F6-3299cc 3.3L SOHC Turbo (1992)
Ignition Control Module: Description and Operation
EZ-69 IGNITION CONTROL UNIT
The EZ control unit is based on a hybrid integrated circuit. Microprocessor, signal conditioning unit, pressure sensor and power stage are integrated
into the control unit.
There are three electrical connectors and a manifold pressure sensing connection on the outside of the control unit and is mounted in the engine
compartment.
NOTE: Control unit base plate must be coated with heat dispersion paste whenever removed and refitted, to improve heat dissipation.
STARTING MODE
This mode is recognized by the microprocessor based on engine speed. The firing point is triggered at the positive edge of the pulse generator signal,
approximately 15° BTDC. The control unit shifts from starting mode into operating mode (idle firing angle of 0° ±3° with 0° throttle switch closed)
as soon as 630 rpm is exceeded. If engine speed drops below 330 rpm, the control unit will revert to starting mode.
OPERATING MODE
An idle/thrust curve (0° throttle switch) and an operating ignition map are stored in the ignition control unit. The optimum firing point for each
operating condition is determined taking engine load, engine speed, engine temperature, intake air temperature, 0° throttle switch and fuel selector
switch positions into account.
To adjust the firing point, the negative pulse generator edge of the control signal transmitted to the output stage is delayed by ascertain time interval
calculated for the current speed. The delay tie calculated by the control unit is thus equivalent to the required spark advance. This is how the
maximum firing point advance is determined.
