Vvt (Variable Valve Timing) System - Suzuki DF150 Service Manual

3-32 ENGINE CONTROL SYSTEM

VVT (Variable Valve Timing) SYSTEM

• The VVT system is designed to continuously vary intake valve timing to best fit the engines current oper-
ating condition.
• The intake cam timing sprocket assembly (VVT actuator) is located at the front end of the intake cam-
shaft. The timing sprocket' internal rotor is operated by engine oil pressure. Since the rotor and intake
camshaft is bolted together, the rotor and camshaft move together. Varying the intake valve timing is
accomplished by changing the intake camshaft phase angle relative to the intake cam timing sprocket
using pressurized engine oil applied to the rotor through an ECM controlled oil control valve.
• The oil control valve (OCV) directs engine oil pressure to the advance chamber or retard chamber inside
the intake cam timing sprocket assembly (VVT actuator). The oil control valve operates on a duty cycle
controlled by the ECM.
• The ECM determines the optimum valve timing (advance angle) under various operating conditions
based on engine speed, throttle opening and cylinder wall temperature. These input values are then
used to control the position of the oil control valve (OCV). The ECM also detects the actual advance angle
from the CMP sensor inputs to perform feedback control and accurately maintain the target advance
angle.
Ex. camshaft
Throttle opening angle
Throttle sensor
Cylinder temp. sensor
MAP sensor
ECM
31
46
CMP sensor
In. camshaft
Crankshaft
CKP sensor
ECM
Crank
position
Target
Cylinder temp.
advance
Cam position
Manifold pressure
Feed
back
Actual valve
timing
+12 V
OCV
Rotation direction
Duty
control
Oil control valve (OCV)
Advance
Valve lift
Ex. valve
VVT actuator
Retard
Advance
Oil
pump
filter
Drain
Oil pan
Engine oil pressure
Signal
40˚ movable angle
In. valve
Crank angle
Valve overlap
In.
camshaft
Oil
Retard