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ENGINE 1ZZ-FE ENGINE
6. VVT-i (Variable Valve Timing-intelligent) System
General This system controls the intake camshaft valve timing so as to obtain balance between the engine output, fuel consumption and emission control performance. The actual intake side valve timing is feed back by means of the camshaft position sensor for constant control to the target valve timing.
Camshaft Position Sensor
Engine Coolant Temp. Sensor
Throttle Position Sensor
ECM
Camshaft Timing Oil Control Valve
Mass Air Flow Meter
Crankshaft Position Sensor
169EG35
ECM Crankshaft Position Sensor Mass Air Flow Meter Feed Back Throttle Position Sensor Duty Control
Engine Coolant Temp. Sensor
Camshaft Timing Oil Control Valve
Target Valve Timing
Correction Actual Valve Timing
Camshaft Position Sensor Vehicle Speed Signal
172CR07
ENGINE 1ZZ-FE ENGINE Construction 1) VVT-i Controller
39
This controller consists of the housing driven from the timing chain and the vane coupled with the intake camshaft. The oil pressure sent from the advance or retard side path at the intake camshaft causes rotation in the VVT-i controller vane circumferential direction to vary the intake valve timing continuously. When the engine is stopped, the intake camshaft will be in the most retarded state to ensure startability. When hydraulic pressure is not applied to the VVT-i controller immediately after the engine has been started, the lock pin locks the movement of the VVT-i controller to prevent a knocking noise.
Lock Pin
Vane (Fixed on Intake Camshaft) Intake Camshaft
Housing Oil Pressure At a Stop In Operation
169EG36
Lock Pin
2) Camshaft Timing Oil Control Valve To VVT-i To VVT-i The camshaft timing oil control valve controls the Controller Controller spool valve position in accordance with the duty (Advance Side) (Retard Side) control from the ECM thus allocating the hydraulic pressure that is applied to the VVT-i controller to the advance and the retard side. When the en- Sleeve Spool Valve gine is stopped, the camshaft timing oil control valve is in the most retarded state.
Connector
Drain Drain Oil Pressure Spring Coil Plunger
165EG34
40 Operation
ENGINE 1ZZ-FE ENGINE
D The camshaft timing oil control valve selects the path to the VVT-i controller according to the advance, retard or hold signal from the ECM. The VVT-i controller rotates the intake camshaft in the timing advance or retard position or holds it according to the position where the oil pressure is applied. Operation Vane Camshaft Timing Oil Control Valve Drive Signal Advance Signal When the camshaft timing oil control valve is positioned as illustration by the advance signal from the ECM, the resultant oil pressure is applied to the timing advance side vane chamber to rotate the camshaft in the timing advance direction.
157EG35
Description
Advance
Rotating Direction
VVT-i Controller Housing
ECM
Duty Ratio Oil Pressure
178EG15
Retard Signal When the camshaft timing oil control valve is positioned as illustration by the retard signal from the ECM, the resultant oil pressure is applied to the timing retard side vane chamber to rotate the camshaft in the timing retard direction.
Retard
Rotating Direction
ECM Duty Ratio Oil Pressure
178EG16 157EG36
Hold Signal
ECM
Duty Ratio Oil Pressure
178EG17 157EG37
The ECM calculates the target timing angle according to the traveling state to perform control as described above. After setting at the target timing, the valve timing is held by keeping the camshaft timing oil control valve in the neutral position unless the traveling state changes. This adjusts the valve timing at the desired target position and prevents the engine oil from running out when it is unnecessary.
Hold
ENGINE 1ZZ-FE ENGINE
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D In proportion to the engine speed, intake air volume, throttle position and water temperature, the ECM calculates an optimal valve timing under each driving condition and control the camshaft timing oil control valve. In addition, ECM uses signal from the camshaft position sensor and the crankshaft position sensor to detect the actual valve timing, thus performing feed back control to achieve the target valve timing. " Operation During Various Driving Condition (Conceptual Diagram) A Full Load Performance
Range 4 Engine Load
Range 5
Range 3 Range 1, 2
Engine Speed Operation State Range Valve Timing TDC Objective
162EG46
Effect
Latest timing
During Idling
EX
IN
Minimizing overlap to reduce blow back to the intake side
Stabilized idling rpm Better fuel economy
BDC
178EG18
To retard side
At Light Load
EX
IN
Decreasing overlap to eliminate blow back to the intake side
Ensured engine stability
178EG19
To advance side
At Medium load
EX
IN
Increasing overlap to increase internal EGR for pumping loss elimination
Better fuel economy Improved emission control
178EG20
42 Operation State Range
ENGINE 1ZZ-FE ENGINE Valve Timing
TDC
Objective
Effect
In Low to Medium Speed Range with Heavy Load
EX
IN
To advance
Advancing the intake valve close timing for volumetric efficiency improvement
Improved torque in low to medium speed range
BDC side178EG21
In High Speed Range with Heavy Load
EX
To retard side
IN
Retarding the intake valve close timing for volumetric efficiency improvement
Improved output
178EG22
Latest timing
At Low Temperatures
EX
IN
Minimizing overlap to prevent blow back to the intake side for reduction of fuel increase at low temperatures, and stabilizing the idling rpm for decreasing fast idle rotation
Stabilized fast idle rpm Better fuel economy
178EG23
Latest timing
Upon Starting/ Stopping the Engine
EX IN
Minimizing overlap to minimize blow back to the intake side
Improved startability
178EG24
