The 1AZ has aluminum cylinder block with cast iron liners. It
features offset cylinder and crank centers. The
engine got the forged steel crankshaft, fully balanced by eight
counterweights. The crankshaft is attached to
the block by five main bearings. Between first and second bearings
there is a gear driven two balancing
shaft in the lower aluminum crankcase. The applying of balancing
shafts was a big step in reduction of
engine vibration. Helical gears are made from polymeric material
for the reduction of noise.
On top of the block there is aluminum DOHC 16-valve cylinder head.
The intake camshaft is equipped with
VVTi system (Toyota variable valve timing system), altering timing
by 50 deg. Camshafts are driven by a
single-stage roller timing chain. The angle between intake valves
and exhaust valves is 27.5 deg. Intake
valve diameter is 34.0 mm (1.3 in), and for exhaust valve - 29.5 mm
(1.2 in). Valve lift is 8.0 mm (0.3-in) for
both valve types. There are not hydraulic lifters.
The engine equipped with sequentially injected fuel system. Each
fuel injectors has twelve small injection
holes (0.18 mm or 0.01 in). The intake manifold is made from
plastic. The exhaust manifold and catalytic
converter is one unit.
Compare to predecessor, the 1AZ has high efficiency and fuel
economy, low noise and vibration levels, light
weight and compact design, good reliability. The engine has older
brother the 2AZ-FE. The 1AZ is
superseded by the newest 3ZR-FE engine since 2007.