Yamaha F225F, Service Manual

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2-9
TECH
FEA
Technical features and description
Basic ignition timing
The basic ignition timing is divided into 3 types: engine starting ignition timing, idling basic ignition
timing, and normal basic ignition timing.
Ignition timing restriction
The advancing or retarding of the ignition timing is restricted according to the engine speed, engine
temperature, and dashpot function.
Ignition timing compensation
The ignition timing control makes advance or retard compensations to the ignition timing according
to the engine operating conditions. The compensations are determined according to the signals
from the following sensors.
Basic ignition timing Criteria Ignition cylinder
Engine starting ignition timing
(BTDC 10°) Engine is starting (less than
500 r/min) All cylinders simultaneously
Idling basic ignition timing Engine speed is at engine idle
speed Each cylinder sequentially
Normal basic ignition timing Engine speed is more than
engine idle speed Each cylinder sequentially
Restriction Corresponding sensor Details
Engine speed restriction Pulser coil The ignition timing is restricted
between BTDC 50° (advance
angle) and ATDC 20° (retard
angle) according to the engine
speed.
Engine temperature restriction Engine temperature sensor The ignition timing is restricted
between BTDC 50° (advance
angle) and ATDC 30° (retard
angle) according to the engine
temperature.
Dashpot function restriction
(when the throttle valve is
closed quickly) Pulser coil and LPS The ignition timing is restricted
to ATDC 20° when the
dashpot function operates.
Compensation Corresponding sensor
After start-up Engine temperature sensor
For stable idle speed LPS and pulser coil
During dashpot function operation LPS, SPS, and pulser coil
For shift-cutout control Pulser coil and SPS
During acceleration Air pressure sensor and TPS