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The control over the ignition advance angle is generally open loop control. But this open loop control is
different from the general open loop control, ECU test the knock signal with the knock sensor while control-
ling and outputting ignition advance angle orders in way of open loop. Once the knock occurs, it is converted
into closed loop control, and its feedback signal is knock sensor signal. Therefore, basically, it is also a closed
loop control.
Section 2 System Component and Working Principle
ECU receives information from the sensors and sends control signals to actuators after processing and
analyzing these information. It plays a role of nerve center in the electronic control system.
ECU hardware consists of input level, micro-computer and output level (see figure 153).
Figure 153
Ignition advance angle control
Starting condition ¡ª fixed ignition advance angle
Running condition
Special control
advance angle basic value - determined by MAP
advance angle correction
instantaneous correction
stable idle correction
air fuel ratio feedback correction
engine overheat correction
knock control
maximum advance/delayed angle control
other correction
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