V6 Engine AJ-V6/AJ28
20to each VVT unit is supplied via fixed oilways in
the cylinder head and not through a separate
bush carrier. This arrangement requires a feed
through the camshaft side of the VVT unit from
the main cylinder head supply. The oil feed is
controlled by the VVT oil control valve, a solenoid
operated shuttle valve, which is bolted directly to
the cylinder head. From the oil control valve, the
flow is via the thrust bearing cap, through
drillings in the camshaft and then through the
hollow fixing bolt which secures the VVT unit.
Drain holes are provided at the rear (camside)
face of the VVT unit for any residual oil which has
seeped past the piston.
Operation
Operation is similar to that of the two stage V8
VVT system. With the oil control valve open, oil
pressure on the helical drive piston is increased,
rotating the cams to the advanced position.
When the valve closes, oil pressure reduces and
the return spring pushes the piston back to thefully retarded position.
The oil control valve is controlled by a 300Hz
PWM signal from the PCM which sets it to either
the fully open or fully closed position.
J.303.1306
VVT OPERATION
VVT Unit with
oil pressure
VVT oil
control valve
open
VVT oil
control valve
closed
VVT Unit with oil
pressure reduced
J.303.1306
