Lexus ES300 (2002 year). Manual — part 129
ENGINE – 1MZ-FE ENGINE
EG-21
211EG32
TWC
Main Muffler
6. Exhaust Pipe
General
An ultra thin-wall, high-cell ceramic type TWC has been adopted. This TWC enables to improve exhaust
emissions by optimizing the cells density.
2-way exhaust control system is provided to reduce noise and back pressure in the main muffler.
ENGINE – 1MZ-FE ENGINE
EG-22
208EG16
Control Valve Close
Exhaust
Gas
Control Valve Open
Low Engine Speed
Middle to High Engine Speed
2-Way Exhaust Control System
A 2-way exhaust control system is used. This system reduces the back pressure by opening a variable
valve that is enclosed in the main muffler.
The valve opens steplessly in accordance with the operating condition of the engine, thus enabling a
quieter operation at lower engine speeds, and reducing back pressure at higher engine speeds.
1) Construction
The control valve is enclosed in the main-muffler. When the exhaust gas pressure overcomes the spring
pressure, the control valve opens steplessly in accordance with the exhaust gas pressure.
2) Operation
a. When Control Valve is Closed (low engine speed)
Since the pressure in the main muffler is low, the control valve is closed. Hence exhaust gas does not
pass the bypass passage, and exhaust noise decreased by the main muffler.
b. When Control Valve is Open (middle to high engine speed)
The valve opens more as the engine speed and the back pressure in the muffler increase. This allows
a large volume of exhaust gas to pass the bypass passage, thereby substantially decreasing the back pres-
sure.
ENGINE – 1MZ-FE ENGINE
EG-41
211EG17
157EG23
Throttle Position Sensor
Camshaft Timing Oil Control Valve
VVT Sensor
Camshaft Timing Oil Control Valve
VVT Sensor
Engine Coolant Temp.
Sensor
ECM
Mass Air
Flow Meter
Crankshaft Position Sensor
Crankshaft Position Sensor
Mass Air Flow Meter
Throttle Position Sensor
Engine Coolant Temp. Sensor
VVT Sensor
ECM
Target Valve Timing
Feedback
Correction
Actual Valve Timing
Camshaft Timing
Oil Control Valve
Duty Control
9. VVT-i (Variable Valve Timing-intelligent) System
General
The VVT-i system is designed to control the intake camshaft within a wide range of 60
(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 reduction of exhaust emissions. The actual intake valve
timing is feedback by means of the camshaft position sensor for constant control to the target valve timing.
ENGINE – 1MZ-FE ENGINE
EG-42
211EG18
Engine Speed
Throttle Opening Angle
ECM
VSV
Actuator
Intake Air Control Valves
Actuator
VSV
To Surge Tank
Vacuum Tank
10. ACIS (Acoustic Control Induction System)
General
The ACIS is realized by using a bulkhead to divide the intake manifold into 3 stages, with an intake air con-
trol valves in the bulkhead being opened and closed to vary the effective length and intake area 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.
System Diagram
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