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Toyota Variable Valve Timing. VVT-i (Gen II)

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Eugenio,77
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Jan 2016

Toyota Variable Valve Timing. Evolution

Conditional 2nd gen. type - timing drive by belt for both camshafts, continuous variable valve timing mechanism with helical splines in the intake camshaft pulley. Applied for engines: 1JZ-GE type'96, 2JZ-GE type'95, 1JZ-GTE type'00, 3S-GE type'97. There was a version with variable valve timing mechanisms at both camshafts - the first Toyota Dual VVT (3S-GE type'98).


VVT-i system (Variable Valve Timing - intelligent) allows to smoothly change the valve timing according to engine operating conditions. This is achieved by rotating the intake camshaft relative to the drive pulley in the range of 40-60° (crankshaft rotation angle).


Timing drive (JZ series). 1 - VVT actuator, 2 - VVT control solenoid, 3 - camshaft position sensor, 4 - crankshaft position sensor.

Variable valve timing actuator

VVT actuator housing (inner splines) is connected to the pulley, central gear (outer splines) is connected to the intake camshaft. There is a movable piston with inner and outer splines between them. During the axial movement of the piston the shaft rotates smoothly relative to the pulley.

JZ series. 1 - housing (inner splines), 2 - pulley, 3 - piston, 4 - outer splines, 5 - piston outer splines, 6 - intake camshaft.

Timing drive (JZ series). 1 - intake camshaft, 2 - spool, 3 - plunger, 4 - VVT control solenoid, 5 - oil path (from oil pump), 6 - cylinder head, 7 - piston outer splines, 8 - piston, 9 - VVT actuator, 10 - piston inner splines, 11 - pulley.

ECM controls the oil flow to advance and retard chambers by solenoid, based on the signals of the sensors. When engine stopped the valve spool is moved by spring to ensure maximum retard angle.

a - spring, b - sleeve, c - valve spool, d - to actuator (advance chamber), e - to actuator (reatrd chamber), f - drain, g - oil pressure, h - coil, j - plunger.

Advance. ECM switches solenoid to an advance position and shifts the spool of the control valve. Engine oil under pressure is supplied to piston left side and moves it to right. When moving at helical splines, the piston turns the camshaft in the advance direction.


Retard. ECM switches solenoid to an retard position and shifts the spool of the control valve. Engine oil under pressure is supplied to piston right side and moves it to left. When moving at helical splines, the piston turns the camshaft in the retard direction.


Hold. After the set position is achieved, ECM switches the solenoid to the neutral position, retaining the pressure on both sides of the piston.




Operation modes

Mode # Timing Condition Effect
Idling 1 Most late opening of the intake valves (maximum retard angle). Minimal valves overlap. Minimal exhaust gas amount by-pass to intake. Stable idle. Reduced fuel consumption.
Low load 2 Minimal valves overlap. Minimal exhaust gas amount by-pass to intake. Stable engine running.
Medium load 3 Valves overlap increases. Reduced pumping losses. Some exhaust gases are by-passed to intake (internal EGR). Reduced fuel consumption. Reduced emissions.
High load, low to medium rpm 4 Early closing of the intake valve to improve volumetric efficiency. Increased torque at low and medium rpm.
High load, high rpm 5 Late closing of the intake valve to improve volumetric efficiency. Increased maximal output.
Low temperature 6 Minimal valves overlap. Reduced fuel losses. Stable idle. Reduced fuel consumption.
Starting and stopping - Minimal valves overlap. Prevention of exhaust gases by-pass to intake. Improved starting conditions.


Valve timing (JZ series)


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