The Electronic Spark Advance provides electronically controlled spark advance and eliminates the need for mechanical and vacuum advance controls in the distributor. The Spark Control Computer uses as many as six sensors to monitor the engines conditions so that it can fire the spark plugs at the proper time.
SPARK CONTROL COMPUTER (SCC)
The Spark Control Computer is the heart of the entire system. It gives the capability of igniting the fuel mixture according to different modes of engine operation by delivering an infinite amount of variable advance curves. During cranking, an electrical signal from the distributor is fed into the computer. This signal will cause the computer to fire the spark plugs at a fixed amount of advance. Once the engine starts, the timing will now be controlled by the computer based on the information received from the various sensors.
The amount of spark advance is determined by three factors, coolant temperature, engine speed, and manifold vacuum. The computer determines spark advance in the following manner:
1. Coolant temperature modifies vacuum advance schedule. There is a different schedule for hot and for cold engines.
2. Advance from vacuum is programmed into computer. In a cold or warm engine spark advance depends only on amount of manifold vacuum. In a hot engine spark advance depends on both manifold vacuum and engine speed.
3. Advance from speed is programmed into computer and depends only engine speed.
The Electronic Spark Control System incorporates the following sensors:
1. The Hall Effect Pickup assembly, located in distributor, supplies basic timing signal and engine speed to computer.
2. The coolant sensor, located on thermostat housing, gives computer information on engine temperature.
3. A carburetor switch located on end of idle stop tells computer when engine is at an idle.
4. The vacuum transducer is located on the Spark Control Computer and tells computer how much vacuum engine is producing.
5. The oxygen sensor (used with Feed Back carburetor only) is located in exhaust manifold and informs computer about oxygen in exhaust so it can alter air/fuel mixture.
6. A charge temperature switch (on 6 cyl. Engines only) is located on intake manifold and monitors intake air temperature.
Tuesday, August 30th, 2011 AT 9:36 PM