MODULAR 3- AND 4-CYLINDER ECOTEC
ENGINES; 11 VARIANTS FROM 1.0L TO 1.5L
~Design and engineering
details
The new Ecotec engines represent a
clean-sheet design and engineering process, leveraging the diverse experience
of GM’s global resources.
All variants feature an aluminum cylinder
block and head, which help reduce the vehicle’s overall mass to enhance
performance and efficiency, while technologies such as central direct fuel
injection; continuously variable valve timing; and variable intake manifold
airflow complement the efficiency goals with broad power bands for an optimal
balance of strong performance and low fuel consumption.
Modularity in parts—such as four-cylinder and
three-cylinder blocks—that share bore spacing, bore diameter, liners, block
height and other dimensions, reduces complexity and increases the flexibility
to quickly adapt the architecture for new applications. Shared rotating parts
among several of the variants, as well as common fuel- and valvetrain-system
components and other engine-driven accessories, also reduce complexity.
~Lightweight and durable
foundation
A lightweight, high-pressure die-cast
aluminum block is the engines’ foundation, matched with an aluminum bedplate
that enhances strength and helps reduce vibration. The high-pressure casting
method produces a more dimensionally accurate block that requires fewer
machining operations than conventional sand-cast blocks.
For structural stiffness, the block has
cast-in-place iron cylinder liners. The bedplate bulkheads also contain
cast-in, nodular iron inserts for localized structural stiffness. A die-cast
aluminum oil pan contributes additional structural strength.
Each engine features 2.9-inch (74 mm)
cylinder bores on 3.19 (81 mm) bore centers and comparatively long piston
stroke lengths that contribute to their strong torque. The 1.0L three-cylinder
has a 3.0-inch stroke (77.4 mm) and the 1.4L four-cylinder engine has a
3.2-inch stroke (81.3 mm), while the 1.5L four-cylinder has a 3.4-inch (86.6
mm) stroke.
Bay-to-bay breathing, which enhances
performance through reduced windage in the crankcase, is enabled through holes
cast in the top of the bulkheads and through passages cast where the block and
bedplate meet. Cast passages for oil and blow-by management and a 4 mm wall
thickness combine to reduce the overall weight of the block assembly, enhancing
vehicle performance and efficiency.
~Strong rotating assembly
Because of higher combustion pressures and an
emphasis on refinement, a premium forged steel crankshaft is used in all
turbocharged and naturally aspirated direct-injection engines for strength and
low vibration. Port-fuel-injected naturally aspirated variants, which have
lower combustion pressures, use a durable cast iron crankshaft with hollow-cast
cores for lower weight.
The complementing rotating assembly
components include durable powder-metal steel connecting rods and
hypereutectic-alloy aluminum pistons that are tough and contribute to
quietness. They are used with low-tension rings that reduce friction, which
contributes to greater efficiency.
Additionally, the 1.0L variant features a
balance shaft mounted inside the oil pan to quell the unique vibration
characteristics of a three-cylinder arrangement.
~Efficiency-enhancing oiling
system
A variable-flow oiling system helps maximize
fuel efficiency. Rather than the linear operation of a conventional fixed-flow
pump, it is accomplished with a crankshaft-driven oil pump that matches the oil
supply to the engine load. The pump changes its capacity based on the engine’s
demand for oil. This prevents using energy to pump oil that is not required for
proper engine operation.
The flow volume of the oil pump is designed
to support the oiling requirements for piston cooling and camshaft phasing. The
cam phasers are supplied with oil through separate bores in the cylinder block
and head. The recirculation of the increased amount of oil in the cylinder head
is permitted through additional pre-cast oil return channels.
Piston-cooling oil jets are used to minimize
piston temperatures, helping to optimize performance, efficiency and emissions.
The jets are part of the engine’s oiling circuit, mounted at the bottom of each
cylinder, and spray engine oil at the bottom of the pistons.The balance shaft for three-cylinder variants
is integrated with the oil pump.
~Integrated DOHC cylinder
head and exhaust manifold
The new Ecotec engines feature an integrated
aluminum cylinder head/exhaust manifold, which further reduces weight—an
attribute that contributes to increased vehicle efficiency and a more favorable
front-to-rear weight balance, for a more responsive driving experience.
The cylinder head features a water-cooled
exhaust manifold integrated within the aluminum casting. Its single-piece
design provides a number of benefits, including quicker engine warm-up, which
contributes to better emissions performance. It also enhances durability by
eliminating the need for gasket sealing around the exhaust ports, as well as
offering under-hood packaging advantages.
Dual overhead camshafts, operating four
valves per cylinder with low-friction, hydraulic roller finger followers, are
hollow in sections to save weight, and are driven by a timing chain with
automatic hydraulic tensioning. Aluminum cam phasers enable variable timing for
the opening and closing of the inlet and exhaust valves, optimizing fuel
consumption and performance under a wide variety of engine load conditions.
A hard-mounted aluminum cam cover features an
integrated oil separation system, which serves as the main body for the engine
positive crankcase ventilation system—an essential contributor for optimal
combustion control. Passages integrated in the cylinder block and cylinder head
enable flow of blow-by gases from the crankcase into the oil separation
chamber, as well as drainage of the separated oil back to the crankcase. The
cam cover assembly also incorporates the oil control valves for the cam phasers
and camshaft position sensors. The unique combination improves packaging in the
engine and reduces complexity of the cylinder head.
~More-precise central direct injection.
Central direct fuel injection is used on some of the
new Ecotec engines and is a primary enabler of their balance of performance and
efficiency. The central location of the six-hole fuel injector, directly above
the piston head (held at a narrow, 6-degree angle), further enhances the
advantages of direct injection by delivering a more precise and even spray
pattern—particularly with the four-valve-per-cylinder arrangement of the cylinder
head. This enables the flow rate of the injectors to be reduced slightly,
reducing consumption and boosting efficiency.
Direct injection moves the point where fuel
feeds into an engine closer to the point where it ignites, enabling greater
combustion efficiency. It also reduces cold-start hydrocarbon emissions,
compared to similar port-fuel-injected engines.
A higher compression ratio is possible
because of a cooling effect as the injected fuel vaporizes in the combustion
chamber. This reduces the likelihood of spark knock. The fuel injectors have
been developed to withstand the greater heat and pressure inside the combustion
chamber, and feature multiple outlets for enhanced injection control.
A cylinder head-mounted pump supplies fuel to
the injectors at up to 2,900 psi (20 MPa). The pump is driven by a three-lobe
cam on three-cylinder engines and a four-lobe cam on four-cylinder engines.
The engine-mounted fuel pump also uses
dedicated control algorithms developed for the on/off control valve, enabling
greater control of the valve needle at low speeds and low rpm, for lower noise
and more consistent performance at lower speeds.
~Math-modeled combustion
system
An advanced combustion system on
direct-injected variants combines a sculpted piston design with a comparatively
small combustion chamber in the head to support the high-compression, mixture
motion parameters enabled by central direct injection. Compression ratios vary
among the Ecotec variants, but are as high as 12.5:1 on some engines, which enables
greater specific output.
The pistons feature unique sculpted
topography optimized via extensive analysis to direct the fuel spray precisely
for a more complete combustion. The contours of the piston heads are machined
to ensure dimensional accuracy—essential for precise control of mixture motion
and the compression ratio.
General Motors employed one-dimensional and
three-dimensional math-based models to refine the parameters of the combustion
system design. The modeling helped determine the optimal 6-degree injector
angle, as well as the shape of the chamber itself and the complementing piston
dish, which is shaped to help direct the fuel spray for a more complete burn of
the mixture.
Three-dimensional analysis also helped
determine the optimal shape and length of the intake ports in the cylinder
head, which feature a high-tumble design that promotes a more homogeneous
mixture in the chamber.
~Turbocharger system
Leveraging the design advantages of the
integrated cylinder head/exhaust manifold, the turbocharger is more closely
coupled to the engine, for quicker response that greatly reduces the lag that
accompanies some turbo systems.
The system uses a comparatively small,
low-inertia turbocharger (water-cooled) engineered to provide strong power at
low rpm and immediate-feeling throttle response. It’s a single-stage,
single-scroll unit used with an intercooler and pressure-activated wastegate.
The diameter of the turbine wheel is only 35 mm, while the low-hiss compressor
measures only 40 mm in diameter—an optimal combination that helps the engine
deliver 90% of maximum torque at only 1,500 rpm for the 1.4L variant.
The turbo feeds the engine through
high-tumble intake ports, which facilitate early combustion phasing, a short
burn duration and good combustion stability. That means there is less need for
spark retard at maximum boost pressure to avoid detonation, which can reduce
performance.
~Variable intake system
A two-stage variable intake manifold is used
on some naturally aspirated variants to further enhance fuel economy and
performance. At engine speeds below 5,000 rpm (at full load) inlet air passes
through intake tracts that increase torque. At speeds greater than 5,000 rpm, a
butterfly valve within the lightweight composite intake manifold opens to
create a shorter intake path, enabling the engine to produce maximum
horsepower.
This two-stage manifold helps the engine
produce approximately 90% of peak torque from 2,200 rpm to 6,000 rpm.
~Refinement. The all-new Ecotec engines have a quiet component set
that contributes to smoothness and quietness, including:-
·
Engine block and bedplate:-
The new Ecotec architecture’s refinement is
rooted in its all-aluminum cylinder block, which is acoustically designed to
reduce airborne and structure-borne operating noise. The structure is so good
at quelling noise and vibration, the need to mask the transfer of engine noise
with in-car sound insulation and other attenuation components is significantly
reduced, which helps reduce the vehicle’s weight.
A bedplate
provides stiffness to the bottom of the cylinder block and incorporates the
main bearing caps—components used to secure the crankshaft within the block.
Iron inserts cast into the bedplate enhance the structure at the main bearings,
for greater smoothness and quietness. The insert material ensures close main
bearing tolerances over a wide range of engine operating temperatures, for
quieter engine lower-end noise.
·
Forged crankshaft:-
In turbocharged
applications, a forged steel crankshaft is used to support the greater
combustion pressures of forced induction with excellent durability, as well as
enhance refinement with vibration-resistant performance—particularly at mid-
and high-rpm levels, when the engine is producing maximum boost. The crankshaft
is used with main bearings featuring tight tolerances that also contribute to
good sound quality.
·
Oil jets:-
Piston-cooling oil
jets not only enhance performance and durability, they provide an extra layer
of oil on the cylinder walls and piston wristpins at start-up, which dampens
noise emanating from the pistons.
· Aluminum oil pan with a steel sump:-
A two-piece oil pan is composed of a
structural, die-cast aluminum upper section, where it attaches to the cylinder
block. The lower section features a coated, stamped steel sump—a design that
helps reduce engine noise, because the steel section dampens noise better than
an all-aluminum pan.
·
In-pan oil pump assembly and balance shaft:-
·
Mounting the oil pump assembly inside the oil pan reduces noise from
the front cover area – an aluminum-intensive area that transmits noise – and
minimizes the potential for pump cavitation noise.
On three-cylinder
variants, a balance shaft is used to achieve four-cylinder-like sound and
vibration qualities. It is mounted inside the oil pan and operates with the oil
pump.
Inverted-tooth camshaft drive chain:-
The camshaft drive
chain is optimized for low sound levels through an inverted-tooth design, which
is significantly quieter than a roller-type chain. As its name implies, an
inverted-tooth chain has teeth on its links—two-pin rolling pivot joints—that
essentially wrap around the gear sprocket to take up virtually all the tension.
This allows for smoother meshing of the chain links to the sprocket teeth, the
cause of most noise in chain drive systems. The chain-to-sprocket tooth impact
is greatly reduced with the inverted-tooth design (also known as a silent chain
drive), substantially reducing noise and enhancing durability.
·
Camshaft drive system:-
In addition to the inverted-tooth camshaft
drive chain, the entire chain-drive architecture, including its tensioning,
wrap and guides, is designed for reduced overall noise radiation and the
elimination of many perceived abnormal sounds. The tensioner is designed to
never require adjustment, ensuring optimal chain tension and low noise
performance for the life of the engine.
·
Structural camshaft and engine front covers:-
·
As a cast-aluminum part mounted on the very top of the engine assembly,
the camshaft cover can be a significant source of noise. That’s not the case
with the new Ecotec family, thanks to a structural cover design that mounts
directly to the engine to enhance its overall stiffness—an attribute that helps
push the engine’s sound frequency above 2,000 hertz. This frequency is
attenuated easily with the acoustic treatment of the top engine cover,
providing a lower overall radiated engine noise level as well as sound quality
that is pleasing to the ear.
Similar to the
structural camshaft cover, the front cover, which covers both the camshaft
drive system and balancer drive systems, was designed with ribbing and other
features to provide a stiffer, more rigid and quieter cover that contributes to
lower engine noise.
·
Front-end accessory drive:-
The front-end
accessory drive features an overriding alternator coupler to remove the effect
of crankshaft oscillations. Along with refinement benefits, it also allows a
reduction in tensioning force to reduce friction levels and improve efficiency.
·
Isolated fuel rail and fuel injectors:-
To reduce the
noise associated with the high-pressure fuel system of direct injections, the
injectors are suspended and the fuel rail is attached to the cylinder head with
rubber-isolated, compression-limiting mounting provisions. This ensures there
is no metal-to-metal contact and prevents the transmission from pulsing energy
through the engine structure. The fuel pump and fuel line are also acoustically
optimized.
·
Quieter turbo system:-
On turbocharged
variants, the design of the turbocharger compressor reduces the characteristic
whistle or hiss sound associated with turbo systems. Passengers feel the
application of power as the turbocharger produces boost, but without the
typical sound associated with it.
VIDEO:-
https://www.youtube.com/watch?v=40fKJ-5DIMs
