Computers and Control Systems: Description and Operation

Digifant System:

PURPOSE
The Digifant I system, provides precise control of fuel injection and ignition systems to ensure optimum performance and strict emissions compliance.

OPERATION
Various engine sensors and other systems (i.e.. air conditioning, auto transmission etc.) supply the Digifant I Control Module with operating information. The Digifant I Control Module processes the sensor input and sends output signals to adjust injector pulse width and ignition timing.

Inputs signals include:
^ Engine Speed (Hall Sensor)
^ Power Supply Relay
^ Ignition Switch Voltage
^ Intake Air Temperature
^ Engine Coolant Temperature
^ CO Potentiometer (early models only)
^ Throttle Position Potentiometer
^ Heated Oxygen Sensor
^ Battery Voltage
^ Vehicle Speed
^ On-Board Computer (OBC)
^ A/C Compressor Signal

Output Signals include:
^ Fuel Injection Control
^ Ignition Control
^ Idle Speed Control
^ Fuel Pump Control
^ Evaporative Control
^ Air Injection
^ Cold Start Injector Control

ON-BOARD DIAGNOSTICS
In the event of a Digifant I system malfunction, circuit information will be stored in the internal memory of the Digifant I Control Module. Intermittent failures are stored with a record of the failure frequency.

The Digifant I Control Module is able to store up to five malfunctions, and will give priority to those items which can cause the vehicle to exceed exhaust emission standards. In addition to being stored in memory, an emissions-related failure will cause the "Check Engine" light to illuminate on the instrument cluster.

ADAPTIVE CONTROL
The Digifant I Control Module has adaptive idle speed and air/fuel mixture capabilities. The Control Module continuously compares the programmed data, for idle control and air fuel mixture, with the input values.

If a deviation occurs, the new input values are superimposed and stored in the programmed data map. As a result, new output signals are sent to the idle control valve, and or to the injectors. This allows the Digifant I Control Module to correct the idle speed, or injector pulse width for break-in wear or slight air leaks which might occur in the systems.

If power is interrupted to the Control Module, new adaptation takes place within several minutes of engine operation.