5000S Wagon L5-2309cc 2.3L SOHC (NF) (1988)
Distributor Advance Unit: Description and Operation
Fig. 15 "Regular Fuel" Ignition Map
Fig. 16 "Premium Fuel" Ignition Map
The ignition timing is determined by the ignition control unit based on inputs from various sensors. The basic timing is calculated according to;
Engine speed
Engine load
Ignition timing is advanced as engine speed increases, and the amount of advance is reduced as engine load increases.
Two different timing maps are stored in the control unit memory, one for regular (low octane) fuel, Fig. 15, and one for premium (high octane) fuel, Fig.
16.
The engine will develop the same horsepower when operated with either fuel, but will develop slightly greater torque when high octane fuel is used.
The ignition control unit will initially run with the premium timing map whenever the engine coolant is greater than 65°C (149°F). If the knock sensor
senses detonation ("pinging") repeatedly, the ignition control unit will automatically switch to the timing map for regular fuel. The ignition control unit
will switch back to the premium fuel timing map after a certain amount of time, or when the engine is restarted.
Fig. 17 Ignition Advance Graph
If the knock sensor detects detonation in a cylinder, the ignition control unit will go through a set of pre-programmed steps to keep the timing as