1UZ-FE VVT-i 4L V8
1UZ-FE VVT-i 4L V8
The 1UZ-FE adopted the VVT-i (Variable Valve Timing – intelligent) and ACIS (Acoustic Control Induction System) system to improve the performance and reduce fuel consumption and reduce emissions. They also adopted the ETCS-i (Electronic Throttle Control System – intelligent) to improve comfort and ensure excellent controllability.
Engine Specifications and Performance Curve
- No. of Cyls. & Arrangement
- 8 Cylinder, V-Type
- Valve Mechanism
- 32 Valve DOHC, Belt and Gear Drive
- Combustion Chamber
- Pentroof Type
- Cross – Flow Type
- Fuel System
- 3969 cc
- Bore x Stroke
- 87.5 x 82.5
- Compression Ratio
- 10.5 : 1
- Max Output
- 216 kW/290 HP @ 6000 rpm
- Max Torque
- 407 Nm @ 4000 rpm
- Fuel Octane
- 96 RON
- An upright Intake port was adopted to improve the intake efficiency.
- A taper squish configuration was adopted to improve the combustion efficiency.
- A steel laminate head gasket is used to improve reliability.
- The cylinder block and the crankshaft have been stiffened to reduce operating noise.
- The skirt portion of the piston was changed in shape and a resin coating applied to reduce friction.
- The VVT-i system is used to improve the fuel economy, the engine performance and it helps reduce emissions.
- The shims were changed from outer type to inner type.
- The diameter of the intake and exhaust valves was increased to improve flow of intake air and exhaust gases.
- Reinforcement ribs were added to the No 1 oil pan to improve rigidity of the coupling of the engine with the transmission, and to reduce noise.
- The diameter of the opening valve in the thermostat has been increased to aid with cooling performance.
Intake and Exhaust System
- A longer port intake manifold is used to improve torque in the low to mid speed range.
- ACIS (Acoustic Control Induction System) is used to increase power output in all engine speed ranges.
- An air assist fuel injection system was adopted to improve atomizing of the fuel for better economy.
- They also used 4 hole injectors to assist again with the atomizing of the fuel for economy.
- The DIS (Direct Ignition System) is used to enhance the reliability of the ignition system
- Iridum tipped spark plugs are now used to improve ignition.
Engine Control System
- ETCS-i is used to improve the controllabilty and comfort of the vehicle.
- The cruise control and the immobiliser have been integrated into the ECU.
Cylinder Head Cover Gasket
- To improve the reliability of the cylinder head cover gasket the cross sectional shape has been changed.
- They changed the intake port to the upright position to improve intake efficiency.
- They adopted a taper squish combustion chamber to improve anti-knocking performance and intake efficiency. On top of this it improved the engine performance and fuel economy.
Cylinder Head Gasket
The Cylinder head gasket was changed from the previous carbon graphite to a steel laminate type to improve the reliability and to reduce the deformation of the cylinder bore. This in tern reduced the consumption of engine oil, it improved the fuel economy and reduced emissions.
Along with the improved engine performance, the piston skirt was changed in shape and a resin coating was applied to reduce friction loss.The piston Head portion adopted a taper squish shape to improve fuel combustion efficiency.
In conjuction with the adoption of the VVT-i system. The camshaft scissor gear has been relocated from the center to the front of the camshaft, an oil passage is provided in the intake camshaft to supply engine oil to the VVT-i system. THe intake camshaft now has a timing rotor to trigger the VVT sensor.
Intake and Exhaust Valve and Valve Lifter
The face diameter of the intake and exhaust valves was increased to improve intake and exhaust efficiency. The Valve stems have been reduced in diameter to reduce the intake and exhaust resistance and to reduce weight. Due to the increase in the amount of valve lift, the valve lifter was changed to in inner shim type, this also meant that the lifter was changed from aluminium to steel. The valve lifter has been made thinner and lighter, it now provides crowning on its side sliding portion to reduce noise and friction. The cross sectional shape of the valve spring was changed from egg shape to a round shape with a smaller diameter for weight reduction.
Timing Belt Cover
The timing belt cover No. 3 is now made of aluminium to reduce noise. The timing belt cover No. 1 and No. 2 are now composite formed with a gasket to improve serviceability.
The adoption of the ETCS-i has realized excellent throttle control. The ISC system, VSC system, and cruise control system are controlled comprehensively by the ETCS-i. Thus, the IAC valve and the sub-throttle valve have been discontinued. A thermostat is installed in the throttle body. The thermostat uses the thermal expansion of the wax to open and close the valve to shut off the flow of warm coolant when the coolant temperature is high in the throttle body’s warm coolant passage. This prevents the throttle body temperature from rising more than the needed level, thus restraining the rise in the intake air temperature.
The low-to mid-speed range torque has been improved by increasing the length of the intake manifold port. The intake air chamber consists of upper and lower sections and contains an intake air control valve. This valve is activated by ACIS (Acoustic Control Induction System) and is used to alter the intake pipe length to improve the engine performance in all speed ranges.
Intake Manifold Gasket
A heat-barrier gasket has been adopted for use between the cylinder head and the intake manifold. This gasket, which restrains the heat transfer from the cylinder head to the intake manifold, helps restrain the intake air temperature and improve the charging efficiency. The construction of the gasket consists of resin that is sandwiched between metal gaskets.
Engine Control System
The engine control system has been changed from that of the ’97 LS400 in the areas described below. The VVT-i, ETCS-i, and ACIS systems have been adopted. The cruise control system and the engine immobiliser system have been integrated with the ECM. A function to communicate with the multiplex communication system has been added.
The engine control system of the 1UZ-FE engine in the ’98 LS400 and ’97 LS400 are compared below.
System Outline ’98 LS400 ’97 LS400
Mass Air Flow Meter
The hot wire type mass air flow meter has been changed to the plug-in type. Its basic operation is the same as that of the previous type.
Crankshaft Position Sensor
The timing rotor of the crankshaft position sensor has been changed from the previous 12 teeth to 34 teeth, with 2 teeth missing. It detects the crankshaft angle at 10 intervals.
Camshaft Position Sensor
The camshaft position sensor is mounted on the left bank cylinder head. To detect the camshaft position, a protrusion that is provided on the timing pulley is used to generate 1 pulse for every 2 revolutions of the crankshaft.
A VVT sensor is mounted on the intake side of each cylinder head. To detect the camshaft position, a timing rotor that is provided on the intake camshaft is used to generate 3 pulses for every 2 revolutions of the crankshaft.
VVT-i (Valiable Valve Timing-intelligent) System
The VVT-i system is designed to control the intake camshaft within a wide range of 50° (of crankshaft angle) to provide a valve timing that is optimally suited to the engine condition, thus realizing improved torque in all the speed ranges and fuel economy, and exhust emissions.
Construction and Operation
- VVT-i Controller
The VVT-i Controller comprises the outer gear that is driven by the timing belt, the inner gear that is affixed to the camshaft and a movable piston that is placed between the outer gear and inner gear. Having helical splines (twisted, vertical grooves) on its inner and outer periphery, the piston moves in the axial direction to shift the phase of the outer gear and inner gear, thus causing the valve timing to change continuously. The VVT tube drives the exhaust camshaft via the scissors gear that is installed on the back.
- Camshaft Timing Oil Control Valve
The camshaft timing oil control valve controls the spool valve position in accordance with
the command of the ECM thus allocating the hydraulic pressure that is applied to the intake camshaft timing pulley to the advance and the retard side. When the engine is stopped, the camshaft timing oil control valve is in the most retarded state.
By the command of the ECM, when the camshaft timing oil control valve is in the position
given in Fig. 1, hydraulic pressure is applied from the left side of the piston, which causes
the piston to move to the right. Because of the twist in the helical splines that are cut out
in the piston, the intake camshaft rotates in the advance direction in relation to the camshaft timing pulley. When the camshaft timing oil control valve is in the position given
in Fig. 2, the piston moves to the left and rotates in the retard direction. Furthermore, the
camshaft timing oil control valve shuts off the oil passages to maintain the hydraulic pressure at both sides of the piston, thus maintaining the phase at that position. This enables the phase to be set to a desired position.
In proportion to the engine speed, intake air volume, throttle position and coolant temperature, the ECM searches an optimal valve timing under each driving condition and control the camshaft timing oil control valve. In addition, the ECM uses signal from the VVT sensors and the crankshaft position sensor to detect the actual valve timing, thus performing feedback control to achieve the target valve timing.
ETCS-i (Electronic Throttle Control System-intelligent)
The ETCS-i system, which realizes excellent throttle control in all the operating ranges, has been
In the conventional throttle body, the throttle valve opening is determined invariably by the amount
of the accelerator pedal effort. In contrast, the ETCS-i uses the ECM to calculate the optimal throttle
valve opening that is appropriate for the respective driving condition and uses a throttle control motor
to control the opening.
The ETCS-i controls the ISC (Idle Speed Control) system, the cruise control system, and the VSC
(Vehicle Skid Control).
A duplicate system is provided to ensure a high level of reliability, and the system shuts off in case
of an abnormal condition. Even when the system is shut off, the accelerator pedal can be used to
operate the vehicle in the limp mode.
Accelerator Pedal Position Sensor
The accelerator pedal position sensor, which is mounted on the throttle body, is integrated with the
throttle lever, which is connected to the cable that extends from the accelerator pedal.
The accelerator pedal position sensor converts the amount of accelerator pedal effort into two types
of electrical signals with distinct output characteristics. The signals are then input into the ECM.
b. Throttle Position Sensor
The throttle position sensor converts the throttle valve opening into an electrical signal and inputs into
the ECM. The output characteristics are the same as those of the accelerator position pedal sensor.
c. Throttle Control Motor
A DC motor with excellent response and minimal power consumption is used for the throttle control
motor. The ECM performs the duty ratio control of the direction and the amperage of the current that
flows to the throttle control motor in order to regulate the opening of the throttle valve.
d. Magnetic Clutch
Ordinarily, the magnetic clutch engages the clutch to enable the throttle control motor to open and
close the throttle valve. In case that a malfunction occurs in the system, this clutch is disengaged to
prevent the throttle control motor to open and close the throttle valve.
The ECM drives the throttle control motor by determining the target throttle valve opening in accordance
with the respective operating condition.
a. Non-linear Control
b. Idle Speed Control
c. Shift Shock Reduction Control
d. TRAC Throttle Control
e. VSC Coordination Control
f. Cruise Control
a. Non-linear Control
Controls the throttle to an optimal throttle valve opening that is appropriate for the driving condition
such as the amount of the accelerator pedal effort and the engine rpm in order to realize excellent
throttle control and comfort in all operating ranges.
In situations in which low-m surface conditions can be anticipated, such as when driving in the snow,
the throttle valve can be controlled to help vehicle stability while driving over the slippery surface.
This is accomplished by turning ON the SNOW switch, which, in response to the amount of the
accelerator pedal effort that is applied, reduces the engine output from that of the normal driving
b. Shift Shock Reduction Control
The throttle control is synchronized to the ECT (Electronically Controlled Transmission) control during
the shifting of the transmission in order to reduce the shift shock.
c. Idle Speed Control
Previously, a step motor type IAC valve was used to perform idle speed control such as fast idle during
cold operating conditions and idle-up. In conjunction with the adoption of the ETCS-i, idle speed control
is now performed by the throttle control motor, which controls the throttle valve opening.
d. TRAC Throttle Control
As part of the TRAC system, the throttle valve is closed by a demand signal from the ABS & TRAC
& VSC ECU if an excessive amount of slippage is created at a driving wheel, thus facilitating the
vehicle in ensuring stability and driving force.
e. VSC Coordination Control
In order to bring the effectiveness of the VSC system control into full play, the throttle valve opening
angle is controlled by effecting a coordination control with the ABS & TRAC & VSC ECU.
f. Cruise Control
Previously, the vehicle speed was controlled by the cruise control actuator, which opened and closed
the throttle valve. Along with the adoption of the ETCS-i, the vehicle speed is now controlled by the
throttle control motor, which controls the throttle valve.
If an abnormal condition occurs with the ETCS-i, the MIL illuminates to alert the driver. At the same
time, the current to the throttle control motor and magnetic clutch are cut off in order not to operate
the ETCS-i. This enables the return spring to close the throttle valve.
Even in this situation, the accelerator pedal can be used to operate the limp mode lever, which operates
the throttle valve to enable the vehicle to be driven in the limp mode.
ACIS (Acoustic Control Induction System)
The ACIS (Acoustic Control Induction System) is realized by using a bulkhead to divide the intake
manifold into 2 stages, with an intake air control valve in the bulkhead being opened and closed to vary
the effective length of the intake manifold in accordance with the engine speed and throttle valve opening
angle. This increases the power output in all ranges from low to high speed.
a. Intake Air Control Valve
The intake air control valve, which is provided
in the middle of the intake manifold in the intake
air chamber, opens and closes to change the effective
length of the intake manifold in two
b. VSV (Vacuum Switching Valve)
Controls the vacuum that is applied to the actuator by way of the signal (ACIS) that is output by the
c. Vacuum Tank
Equipped with an internal check valve, the vacuum tank stores the vacuum that is applied to the actuator
in order to maintain the intake air control valve fully closed even during low-vacuum conditions.
a. When the Intake Control Valve Closes (VSV ON)
The ECM activates the VSV to match the longer pulsation cycle so that the negative pressure acts
on the diaphragm chamber of the actuator. This closes the control valve. As a result, the effective
length of the intake manifold is lengthened and the intake efficiency in the low-to-medium speed range
is improved due to the dynamic effect of the intake air, thereby increasing the power output.
b. When the Intake Control Valve Open (VSV OFF)
The ECM deactivates the VSV to match the shorter pulsation cycle so that the atmospheric air is led
into the diaphragm chamber of the actuator and opens the control valve. When the control valve is
open, the effective length of the intake air chamber is shortened and the peak intake efficiency is shifted
to the high engine speed range, thus providing greater output at high engine speeds.
Function to Communicate with Multiplex Communication System
The ECM communicates with the meter ECU, air conditioning ECU, body ECU, etc., of the multiplex
The main output signals from the ECM are as follows:
Signals from the Indicator Lights in the Speedometer (Oil Pressure Signal, Oil Level Signal and Generator
L Terninal Signal)
Engine Coolant Temp. Signal
Engine Speed Signal
Signals related to the Air Conditioning System (Refrigerant Pressure Signal and Compressor Speed Signal)
The main input signals to the ECM are as follows:
Air Conditioning Signal
Electrical Load Signal (Taillight and Rear Window Defogger System)