Ignition Timing Control System - Yamaha F150B Service Manual

Ignition timing control system

F150B uses ignition timing control system to control the ignition timing and the duration of ignition
coil energization. High output power, improved fuel economy, and low exhaust emissions are
attained by properly controlling the ignition timing and the duration of ignition coil energization in
response to every engine operating conditions, based on the signals from each sensor and the map
data.
Basic ignition timing
computation
Computation for com-
pensation
Ignition timing
restriction
Computing the
duration of
energization
Optimal ignition timing is selected from the map data in accordance with
the signals from each sensor.
Ignition timing is advanced or retarded in response to the engine operat-
ing conditions determined by the signals from each sensor.
Stable idle As the idle speed drops, ignition timing is advanced to
make it stable. Ignition timing is retarded as the idle speed
speed
gets higher.
Start-up Engine startability is improved by applying the advanced
ignition timing at the engine start-up. Subsequently, the
operation
ignition timing is controlled to go back to the standard angle
gradually.
compensati Ignition timing is temporarily retarded at acceleration to
improve the throttle response.
on for
acceleration
Shift-cutout When the conditions are met for implementing the shift cut-
out control, the specified angle is added to the ignition tim-
ing at every updating cycle until it reaches the shift-cutout
compensation angle. Otherwise, the specified angle is sub-
tracted from the ignition timing at every updating cycle until
it reaches 0°CA.
Engine Optimal ignition timing is selected from the map data
depending on the cooling water temperature detected by
temperature
the engine temperature sensor.
restriction
Ignition Limit values for advancing and retarding the ignition timing
are computed by the map data in accordance with the
timing upper
engine speed detected by the pulser coil.
and lower
limits
restriction
The duration of ignition coil energization is controlled based on the engine
speed and the supply voltage to the ignition coil.
Electronic control system
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