Lexus RX300 (MCU15). Manual — part 39
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ENGINE — 1MZ-FE ENGINE
Engine
Front
Cast Iron
Torsional
Damper
Rubber
Steel
Aluminum
187EG14
29
7. Crankshaft
D The crankshaft is made of forged steel and has 4 journals and 9 balance weights.
D All pins and journals fillets are roll-finished to maintain adequate strength.
D The crankshaft bearings for the No. 1 and No. 4 journals are made wider to decrease noise and vibration,
and those for the No. 2 and No. 3 journals are made narrower to reduce friction.
Roll-Finished
Engine
Front
Balance Weight
Oil Hole
No. 1 Journal
No. 4 Journal
187EG13
8. Crankshaft Pulley
D The crankshaft pulley hub is made of aluminum
to reduce weight and vibration.
D The rigidity of the torsional damper rubber has
been optimized to reduce noise.
ENGINE — 1MZ-FE ENGINE
Intake Camshaft
VVT-i Controllers
Exhaust Camshaft
157EG22
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JVALVE MECHANISM
1. General
D Each cylinder has 2 intake valves and 2 exhaust valves.
D The valves are directly opened and closed by 4 camshafts.
D The exhaust camshafts are driven by a timing belt, while the intake camshafts are driven through gears
on the exhaust camshafts.
D The VVT-i system is used to improve fuel economy, engine performance and reduce exhaust emission.
For details, see page 48 (VVT-i System Section).
2. Camshafts
D In conjunction with the adoption of the VVT-i system, an oil passage is provided in the intake camshaft
in order to supply engine oil to the VVT-i system.
D A VVT-i controller has been installed on the back of the intake camshaft to vary the timing of the intake
valves.
D To detect the camshaft position, a timing rotor that is provided on the VVT-i controller is used to generate
3 pulses for every 2 revolutions of the crankshaft.
D The intake camshafts are driven by gears on the exhaust camshafts. The scissors gear mechanism is
used on the exhaust camshaft to control backlash and suppress gear noise.
No. 2 Camshaft (Exhaust)
No. 1 Camshaft (Intake)
No. 3 Camshaft (Intake)
No. 4 Camshaft (Exhaust)
Scissors Gear Mechanism
VVT-i Controllers
Timing Rotor
Scissors Gear Mechanism
187EG15
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ENGINE — 1MZ-FE ENGINE
187EG16
187EG17
Camshaft
Adjusting Shim
Valve Lifter
Valve
Adjusting Shim
Valve Lifter
Cutout
Camshaft Timing Pulleys
No. 2 Idler
No. 1 Idler
(Tension
Adjuster)
Timing Belt Tensioner
Crankshaft Timing Pulley
Water Pump
Pulley
187EG18
31
3. Intake and Exhaust Valve and Valve Lifter
D Narrower valve stems have been adopted to reduce the intake and exhaust resistance and for weight
reduction.
D The adjusting shim has been located directly above the valve lifter. This construction allows the adjusting
shim to be replaced without removing the camshaft, which improves the serviceability during valve clear-
ance adjustment.
D A cutout is provided in the valve lifter to improve the serviceability of replacing the adjusting shims.
" Specifications A
mm (in.)
Item
Intake Valve
Exhaust Valve
Face
Diameter
34.0 (1.34)
27.3 (1.07)
Stem Diameter
5.5 (0.22)
5.5 (0.22)
4. Timing Belt
The timing belt tooth configuration has been de-
signed to help to reduce noise and to enable the belt
to transmit power under high load factors.
ENGINE — 1MZ-FE ENGINE
Tension
Spring
Compression
Spring
187EG19
Belt
Tensioner
Rod
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5. Timing Belt Tensioner
The timing belt tensioner uses a spring and siricon
oil damper, and maintains proper timing belt tension
at all times.
The timing belt tensioner suppresses noise generated
by the timing belt.
6. Timing Belt Cover
The timing belt cover is divided into 3 pieces, designated No. 1 to No. 3. The NO. 1 and 2 timing belt
covers are made of resin, and tightened with evenly spaced bolts. The No. 3 timing belt cover is made
of steel sheet, and is attached to the engine via rubber bushings to reduce noise.
No. 2 Timing Belt Cover
No. 3 Timing Belt Cover
No. 1 Timing Belt Cover
Spaced Bolt
187EG20
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