Development of Toyota 1ZZ-FE Engine

SAE TECHNICAL
PAPER SERIES
981087
Development of Toyota 1ZZ-FE Engine
Shoji Adachi, Kimihide Horio, Yoshikatsu Nakamura,
Kazuo Nakano and Akihito Tanke
Toyota Motor Corp.
Reprinted From: New Engine Design and Automotive Filtration
(SP-1362)
International Congress and Exposition
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February 23-26, 1998
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981087
Development of Toyota 1ZZ-FE Engine
Shoji Adachi, Kimihide Horio, Yoshikatsu Nakamura,
Kazuo Nakano and Akihito Tanke
Toyota Motor Corp.
Copyright © 1998 Society of Automotive Engineers, Inc.
ABSTRACT
2) Lighter in weight
Build the lightest engine among those employing
The 1ZZ-FE engine is a newly developed in-line 4-cylin-
aluminum engine blocks (Fig. 3)
der, 1.8-liter, DOHC 4-valve engine mounted in the new
3) More compact
Corolla. Abounding in new technologies including the
laser-clad valve seat, high-pressure die-cast aluminum
Shorten the overall length of the power plant for
cylinder block, and the small-pitch chain drive DOHC,
possible installation in front-engine, front-drive
coupled with the fundamentally reviewed basic specifi-
vehicles, while reducing the overall height and
cations, the new engine is compact and lightweight, offer-
width.
ing high performance and good fuel economy. Anticipat-
4) Emission regulation compliance
ing even more stringent emission regulations in the
Configure a low-cost, simple construction engine
future, in addition to the revision of the engine body, the
and ensure emission regulation compliance.
layout of the exhaust system has been improved to
5) Vibration and noise
enhance warm-up performance of the converter.
Improve performance and, at the same time,
DESIGN CONCEPT AND TARGET
meet or exceed the level of the previous engine
model which had a good reputation in the mar-
ket.
From the viewpoint of the global greenhouse, one of the
most important tasks for the automotive engine is to
6) Parts reduction
reduce the emission of carbon dioxide by improving fuel
Drastically reduce the number of parts used,
economy. Toyota has already introduced lean burn
thereby reducing the overall weight and cost and
engines, a direct injection gasoline engine and other fuel
improving ease of assembly and cost.
efficient engines into the market. But while these engines
require special devices, it has become more important to
improve fuel consumption by optimizing basic specifica-
tions and adopting new technologies to each component.
Moreover, in order to meet worldwide market demands
and to meet various countries’ emission regulations,
development of this new engine was necessary.
The 1ZZ-FE engine has been developed around the fol-
lowing concepts with the following targets:
(1) To enhance potential for cleaner exhaust emissions
and better fuel economy by optimizing basic speci-
fications.
(2) To improve engine performance and to make its body
even more compact and lightweight by re-examining
each engine component.
1) High performance
Aiming for ease-of-handling, keep maximum out-
put and torque at the top of its class (Figs. 1 and
2), while attaining flat torque characteristics.
Figure 1. Maximum Power Comparison
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SPECIFICATION
Table 1 lists the basic specifications of the 1ZZ-FE
engine. Fig. 4 shows cross-sections of the engine and
Fig. 5 shows the appearance of the engine and a com-
parison of dimensions with the previous engine.
Table 1.
Engine Specifications
Name
1ZZ-FE
Type
Water-cooled, gasoline, 4-cycle
Displacement(cc)
1794
Arrangement & No. of Cylinders
4-cylinder, In-line
Type of Combustion Chamber
Cross-flow, pentroof
Valve mechanism
4-valve, DOHC, chain drive
Fuel system
Multi-point injection
Bore × Stroke(mm)
79.0 × 915
Compression ratio
10.0:1
Valve head dia.
Intake, 32mm ; Exhaust, 27.5mm
Cylinder bore spacing
87.5mm
Crankshaft pin-journal dia.
44.0mm
Figure 2. Maximum Torque Comparison
Crankshaft main-journal dia.
48.0mm
Connecting rod length
146.65mm
Emission control system
TWC, λ-control
Max. power(Kw/rpm)
89/5600
Max. torque(Nm/rpm)
165/4400
Dimensions(L × W × H mm)
639 × 565 × 62
HIGH PERFORMANCE AND GOOD FUEL
ECONOMY
Fig. 6 shows the performance curve of the 1ZZ-FE
engine. Compared with the previous engine, the specific
fuel consumption has been greatly improved over the
entire range. In addition, the engine’s maximum output
and torque have been improved and, at the same time, a
moderate torque curve is achieved by eliminating torque
drops in the low-to-mid-speed range for easy-to-handle
Figure 3. Mass Comparison
output characteristics.
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Figure 4. 1ZZ-FE Engine Cross-Sections
Figure 5. 1ZZ-FE Appearance and Comparison of Dimension
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Figure 6. Engine Performance Curves
Regarding actual vehicle fuel economy, a Corolla with a
4-speed automatic transmission achieved 36.8 mpg on
the U.S. LA#4 combined fuel economy test mode (FTP
Figure 7. Relation of Stroke to Improvement Ratio of
and HFET). This represents an increase of approximately
Fuel Economy
5% over the previous model which had already adopted
various technologies to improve fuel economy.
This estimation is based on the actual specific fuel con-
sumption that was measured by changing the L/R ratio
The following paragraphs elaborate on the new technolo-
(λ=3.0, 3.3 and 3.6 ) of the previous engine. When this
gies incorporated in the engine to achieve said perfor-
ratio is made bigger than necessary, specific fuel con-
mance, along with a discussion of each of the
sumption cannot be further improved. This is because
technologies.
the increase in the connecting rod mass causes 1 friction
to increase. When the stroke is made longer, the piston
BORE AND STROKE – The bore and stroke for the 1ZZ-
speed increases, adversely affecting oil consumption. It
FE engine has been optimized for greater fuel economy
therefore becomes necessary to increase piston ring ten-
and examined in Fig. 7. Line (1) in Fig. 7 shows the ratio
sion. Line (3) of Fig. 7 is the estimate made on the influ-
of improvement in fuel economy over the previous engine
ence of this increased piston ring tension on specific fuel
when the bore and stroke values are varied in the new
consumption. The thick solid line in Fig. 7 is the combina-
engine. It is an estimate based on the relationship
tion of effects (1) through (3). Following a close discus-
between the bore and stroke ratio and the specific fuel
sion, a long stroke ( 79 × 91.5) has been selected with
consumption of ten different Toyota engine models. In the
an L/R ratio of 3.205 for the 1ZZ-FE engine.
estimate, the compression ratio, the L/R ratio ( the ratio of
connecting rod length to crank radius) and the effects of
Although the fuel specification of the 1ZZ-FE engine is
piston ring tension are fixed. It is considered that the
regular gasoline, the adopted high compression ratio
longer the stroke, the more compact the combustion
(10.0:1) has been achieved with a compact combustion
chamber, which results in better thermal efficiency and,
chamber and improved anti-knock quality which is dis-
hence, increased fuel economy. Line (2) in Fig. 7 shows
cussed later. Therefore, fuel economy is consistent with
the estimation of specific fuel consumption over the previ-
high performance.
ous engine when L/R ratio is varied in the new engine. An
appropriate connecting rod length is selected here by fix-
ing the cylinder block maximum height to restrict the
engine’s overall height.
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FRICTION REDUCTION – For the cylinder block, in
order to improve cylinder bore circularity and straightness
during actual operation, a new cooling system, (which is
explained later), has been developed. This, in turn, has
enabled a reduction in piston ring tension. Also passage
holes are provided in the cylinder block wall located
above the crankshaft bearing hole. As a result, the air at
the bottom of the cylinder flows smoother, and pumping
loss (back pressure at the bottom of the piston generated
by the piston’s reciprocal movement) is reduced to
improve the engine’s output. For the crankshaft, in addi-
tion to reduced pin diameter, pin length and journal
length, the precision and surface roughness of the pins
and journals have been improved. Additionally, the crank-
shaft bearings have adopted single-cut turning to further
reduce friction. For the piston, the piston skirt has been
shortened to reduce the sliding surface area. For the
camshaft, the surface roughness of the journals and cam
lobes have been improved and the width of the cam lobes
has been reduced to minimize friction.
LASER-CLAD VALVE SEAT – Fig. 8 shows the cross -
Figure 9. Effect of Laser-Clad Valve Seat
sections of the laser-clad valve seat and the conventional
shrink-fit seat ring type for comparison. The laser-clad
TAPER SQUISH COMBUSTION CHAMBER – The
valve seat is a layer of highly wear-resistant alloy directly
squish area formed by the piston top and cylinder head
formed in the cylinder head body by using a laser. The
bottom surface has been tapered by being inclined along
laser-clad valve seat eliminates the need for a space in
the cylinder head combustion chamber wall (Fig. 10) .
the cylinder head into which separate seat rings are
This taper squish shape reduces the masking portion
shrink-fit. This has enlarged the valve seat diameter both
around the intake valve when it is open, increasing intake
for the intake and exhaust by 1 mm, thus improving the
air volume (Fig. 11). Moreover, in the early stage of com-
induction efficiency over the conventional shrink-fit seat
bustion, this taper squish helps combustion pressure to
ring type. Fig. 9 compares the performance of the laser-
increase gradually and, at the latter part of combustion,
clad valve seat in the pre-prototype stage with that of the
increases the burning velocity (Fig. 12), thereby en-hanc-
shrink-fit seat ring. The elimination of the shrink-fit space
ing anti-knock quality. It is inferred that the increase of
enabled the water jacket to be placed closer to the valve
flow velocity to the squish area promotes the flame prop-
seat, which has helped decrease the temperature of the
agation to the end of the squish area upon piston descent
combustion chamber wall, thereby enhancing anti-knock
(Fig. 13). Fig. 14 shows the benefits of the improved per-
quality. All in all, it has been possible to obtain a valve
formance in the prototype stage.
diameter greater than that of the previous engine’s
despite a more compact combustion chamber and a
smaller bore, thanks to the adoption of the laser-clad
valve seat and the enlarged valve angle.
Figure 10. Taper Squish Combustion Chamber
Figure 8. Adoption of Laser-Clad Valve Seat
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Figure 11. Comparison of Flow Rate Characteristics
Figure 14. Effect of Taper Squish Combustion Chamber
COOLING SYSTEM – The flow of the engine coolant
makes a U-turn in the cylinder block to prevent stagna-
tion, thereby ensuring uniformity of the cylinder bore wall
temperature between the cylinders. The entire coolant
mass flows up from the cylinder block to the front of the
cylinder head and then front to the rear (Fig. 15). This
increases the flow velocity in the cylinder head, which
helps decrease the combustion chamber wall temper-
ature. During the basic planning stage of 1ZZ-FE, CFD
Figure 12. Comparison of Combustion Pattern
was used practically to develop this cooling system con-
struction and these passage areas.
Figure 15. Cooling System
IGNITION SYSTEM – A DIS (Direct Ignition System),
which eliminates the distributor, was adopted in the 1ZZ-
FE engine to improve the ignition timing accuracy with a
high compression ratio and to enhance the overall reli-
ability of the ignition system. This system consists of a
Figure 13. Comparison of Flow Velocity at Squish Area
crankshaft position sensor which directly detects the
(CFD Simulation)
crank position from a sensing plate attached to the front
end of the crankshaft, a phase sensor which detects cyl-
inder number by a boss on the rear end of the intake
camshaft and two sets of ignition coils integrated with the
igniter.
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INTAKE MANIFOLD – An aluminum pipe is used as the
CYLINDER BLOCK – The cylinder block is a high-pres-
intake manifold. It has been bent and shaped into a
sure aluminum die casting of an open-deck con-struction
three-dimensional form, allowing a lightweight and com-
with thin cast-in iron liners. It is 32% lighter than the pre-
pact intake manifold with a large diameter and a long port
vious cast iron block and offers greater production effi-
( 41 × 413) to be employed for improved low-to-mid-
ciency. The water pump swirl chamber, the inlet housing
speed torque. The sections from the throttle body
and by-pass passage lead are integrated into the high-
through each port have been connected in a straight line
pressure aluminum die-cast cylinder block, contrib-uting
to prevent a drop in induction efficiency at high-speed
to a compact body. To counteract casting cavities which
due to turbulence (Fig.16).
can occur in the thick wall portions produced from body
integration and at the crankshaft main journals, the pro-
duction procedure uses a pin to squeeze these thicker
portions (Fig.18).
Figure 16. Intake Manifold
LIGHTWEIGHT AND COMPACTNESS
The following innovative technologies have been incorpo-
rated to make the new engine 23% lighter (Fig.17) and
Figure 18. Cylinder Block
more compact by 15mm in overall length, 27mm in over-
all width, and 19mm in overall height, when compared to
CAMSHAFT DRIVE SYSTEM – The four different chain
the previous engine. The length from the front end of the
drive systems shown in Fig. 19 were considered for
crank pulley to flywheel has also been shortened by
determining the basic specifications. The timing belt in
33mm to make the overall length of the power plant
No.1 is the lightest, though system No.4, which uses a
shorter. This improves the ease of installation in front-
single chain to directly drive both the intake and exhaust
engine front-drive vehicles.
camshaft from the crankshaft, has been found to be
advantageous. It uses a small-pitch (8mm) chain to make
the system affordable in terms of the overall length, the
number of parts used and cost. In drive system No.4, it is
necessary to provide a wider pitch between camshafts
than in drive system No.1 even though the cam sprockets
were made smaller by adopting the small-pitch chain.
Nonetheless, it meets the dimensional requirements orig-
inally planned for 1ZZ-FE and was thus adopted. The
chain cover generally takes up a large percentage of the
chain drive system in terms of mass and cost. In 1ZZ-FE,
the chain cover has been integrated with the water pump
swirl chamber cover and accessories bracket, thereby
realizing an even lighter, more compact cost effective
system than that examined in Fig. 19.
Figure 17. Engine Mass Comparison
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Figure 19. Comparison of Camshaft Drive System
ACCESSORIES LAYOUT – For the accessories drive, a
manifold converter which has traditionally been located
serpentine belt drive system has been employed which
on the front side (Fig. 20). Instead of the conventional
uses a single V-ribbed belt. Since it requires only one
two-hole injectors, the new engine is equipped with four-
crank pulley stage, the overall length has been short-
hole injectors which are capable of atomizing fuel into
ened. Further, the use of a bracket for the exclusive pur-
even finer particles. The injector is mounted in the cylin-
pose of mounting each accessory to the engine body has
der head, thereby reducing the distance between itself
been eliminated for weight reduction. At the same time,
and the combustion chamber. This helps prevent fuel
by not using the bracket, each accessory can be
from adhering to the wall surface at the intake port, thus
mounted closer to the engine, which contributes to an
reducing HC emissions and improving fuel consumption.
overall smaller cross-wise dimension.
This arrangement has made it possible to comply with
the U.S. TLEV emission regulation without using a mani-
OTHER TECHNOLOGIES – The thickness of the fly-
fold converter or a start catalyst and elimination of the
wheel mounting flange on the crankshaft has been
EGR system was also made possible. At the same time,
reduced to shorten the overall length of the power plant.
it has enabled us to cope with future regulations which
The overall height of the engine has been reduced by
will become even more stringent.
changing the shape and layout of the intake manifold.
And the cylinder head cover shape has been changed to
minimize the increase of the overall height by adopting
the longer stroke. In addition to the intake manifold, stain-
less pipe is also used for the exhaust manifold to drasti-
cally reduce the weight of the intake and exhaust
systems. At the same time, these pipes can deform dur-
ing a frontal impact, lengthening the shock absorbence
zone at the front of the vehicle.
CLEAN EMISSIONS
The intake and exhaust systems are laid out in reverse
compared to a traditional layout so that the exhaust man-
ifold is located at the rear of the engine when it is in a
front-engine front-drive vehicle. This made the distance
between the engine and the under-floor converter shorter
and improved the warm-up performance of a converter.
Thanks to this exhaust system layout, the under-floor
Figure 20. Catalyst Warm-up Performance
converter has the same warm-up performance as the
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