Yamaha F225F, Service Manual

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2-11
TECH
FEA
Technical features and description
Knock control
In knock control, the engine ECM receives the knock signal from the knock sensor which is installed
on the cylinder block between the cylinder banks. The engine ECM retards the ignition timing and
decreases the engine speed according to the amount of knocking to protect the engine from dam-
age.
If the knocking occurs frequently, the ignition timing is retarded until the knocking is no longer
detected, and the retarded ignition timing is maintained, using the learning function.
The knock control activates according to the following conditions:
The knock control also activates when the engine temperature sensor is malfunctioning regardless
of the preceding conditions.
Engine
temperature
Less than 20 °C
(68 °F)
20–25 °C (68–77 °F)
More than 25 °C
(77 °F)
Engine speed
Less than 4500 r/min Knock control does
not activate Knock control
activates if conditions
continue for 0.5
seconds Knock control
activates
4500 r/min or more Knock control
activates