Yamaha F150B, Руководство по обслуживанию

Страница: 59 / 458

2-16
Electronic control system
0
1
2
3
4
5
6
7
8
9
10
A
Idle speed control
Engine ECM controls the amount of intake air into the engine at idle by driving the ISC stepper
motor based on the signals from each sensor to regulate the area of the passage bypassing the
main pipe where the throttle valve is installed.
Determination of the ISC valve opening
Based on the signals from each sensor, engine ECM determines the extent to which the ISC valve
must be opened, and controls the ISC stepper motor operation to obtain the target ISC valve open-
ing.
ISC valve
Engine ECM controls the amount of intake air at idle by driving the stepper motor, and changing the
area of the passage bypassing the main pipe where the throttle valve is installed. The stepper motor
moves the ISC valve in 120 steps from fully open position to fully closed position. The ISC valve
opens when the stepper motor is driven in reverse direction, and closes when the stepper motor is
driven in forward direction.
A
Intake air flow
B
Movement of ISC valve
a
ISC valve
b
Intake manifold
ISC valve opening Engine condition
ISC valve opening at engine start At engine start, ISC valve is opened relatively wider depending on the
engine temperature. This increases the amount intake air and
improves the engine startability.
ISC valve opening immediately
after engine start After engine start, the initial ISC valve opening determined by the
engine temperature is reduced in steps and at constant interval until
the idle speed is obtained.
Dashpot ISC valve opening When the throttle lever is pulled back, ISC valve opening is controlled
to prevent the engine speed from dropping off sharply.
ISC valve opening with engine
speed compensation The difference between the actual engine idle speed and the target
engine speed is calculated, and ISC valve opening is altered so that
the target engine speed is obtained.
#1 #2 #3 #4
A
B
a
b