Yamaha F50D Servise Manual - page 43
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Ignition timing control
Control circuit diagram
Basic control
The ignition timing is determined by using the map based on the engine speed (r/min). Then, igni-
tion signals are output from the microcomputer in accordance with the ignition timing map so that
ignition can take place at the optimal timing in relation to the engine speed. Then, the microcom-
puter corrects the ignition timing in accordance with the operating conditions of the engine as
detected by the signals that are input from the engine temperature sensor and oil pressure sensor.
The pulser signals that are output when the protrusions for cylinders #1 and #4, and for cylinders #2
and #3 pass by the pulser coil, are used to calculate the engine speed. In addition, the pulser sig-
nals are used to determine the forecast starting position of the ignition timing.
1
Cylinder identification protrusion
2
Pulser coil
3
Protrusion for cylinders #1 and #4
4
Protrusion for cylinders #2 and #3
5
Pulser coil signal
6
Cylinder identification signal
7
Identification signal for cylinders #1 and
#4
8
Identification signal for cylinders #2 and
#3
9
Rotating direction
Operation
Positive start
Quick acceleration
Damage prevention
Detection
Microcomputer
Engine start
Engine temperature
Ignition timing control
(optimized ignition
timing)
Engine speed control
Alert buzzer
(in remote control
unit)
Alert lamp
(low oil pressure)
Alert lamp
(to overheat)
Engine speed
Oil pressure
Acceleration
Over revolution
Low oil pressure
Overheat
2
3
4
8
7
6
9
1
5
Electronic control system