Yamaha F150B Service Manual page 51

Fuel injection control
Synchronous Simultaneous
injection injection for a
group of
cylinders at
engine start-
up
Group
injection in
normal
operation
Asynchro- Asynchronous
nous injec- injection at
tion acceleration
Simultaneous injection of group cylinders upon starting
Cylinder 1
Compression
Cylinder 3
Cylinder 4
Cylinder 2 Combustion
Pulser coil signal 1
Pulser coil signal 2
Injection #1 and #4
Injection #2 and #3
A
Compression TDC
The fuel injection timing control applicable to the start-up mode
after the cylinder identification is completed by the pulser coil.
Fuel injectors are turned on simultaneously for each cylinder
group (#1 and 4, #2 and 3), synchronized at the crankshaft
angle signal reference point (BTDC 370° CA) or at BTDC 70°
CA in reference to the exhaust TDC.
Fuel injectors are turned on in reference to the exhaust (com-
pression) TDC when only the cylinder group identification is
completed and the engine is not in the start-up mode. The fuel
injectors for a group of cylinders are turned on simultaneously.
Fuel is injected two times in every two rotations of crankshaft.
When the increment of throttle opening gets larger than the set
value in the course of acceleration, for instance, the fuel is
injected immediately and simultaneously at all cylinders, rather
than synchronizing with the engine rotation signal transmitted
by the pulser coil. This prevents the lean air/fuel ratio, and
assures the sharp throttle response in acceleration.
Combustion
Intake Compression
Exhaust Intake
Exhaust
BTDC70° BTDC10°
#1 and #4
BTDC70° BTDC10°
#2 and #3
Electronic control system
Exhaust Intake
Combustion Exhaust
Compression Combustion
Intake Compression
BTDC70° BTDC10°
#1 and #4
BTDC70° BTDC10°
#2 and #3
0
1
2
3
4
Compression 5
Intake
6
Exhaust
Combustion
BTDC70° BTDC10°
7
#1 and #4
8
9
A
10
A
2-8