Download 1 - GM Powertrain

2012 Vortec 5.3L V-8 VVT (LMG)
Vehicle Applications
Chevrolet Avalanche
Chevrolet Silverado
Chevrolet Suburban
Chevrolet Tahoe
GMC Sierra
GMC Yukon
GMC Yukon XL
Product Highlights
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Gen IV iron cylinder block
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High-flow aluminum cylinder heads
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Camshaft phasing
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E85 flex-fuel capability
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Active Fuel Management
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Advanced electronic throttle control
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58X ignition system
Overview
The Vortec 5.3L V-8 (LMG) is a technically advanced small-block V-8 engine that delivers a
great balance of power, torque and efficiency for full-size trucks and SUVs. It is the standard
engine on Chevrolet Avalanche and Suburban 1500 and GMC Yukon XL 1500 models with
2WD; and Chevrolet Tahoe with 4WD. It is available on Chevrolet Silverado and GMC Sierra
pickups.
Variable valve timing helps the 5.3L optimize performance and efficiency and reduce emissions,
while GM’s Active Fuel Management cylinder deactivating technology helps improve fuel
economy in certain light-load driving conditions. It is also E85-capable. In all applications, the
engine is matched with GM’s Hydra-Matic 6L80 six-speed automatic transmission.
A similar 5.3L (LC9) is offered on Chevrolet Avalanche and Suburban 1500 and GMC Yukon XL
1500 models with 4WD; as well as Chevrolet Silverado and GMC Sierra pickups, its primary
difference is its aluminum cylinder block.
The 5.3L represents the fourth-generation of one of the most important and successful engines
in automotive history – the original Chevrolet small-block, which debuted in 1955. The Gen IV
Vortecs feature technology that creators of the first small block could not have imagined, yet
they share one fundamental trait with the original: a market-leading balance of performance,
sophistication, economy and durability.
As with other members of the Gen IV engine family, one of the enablers of the 5.3L’s balance of
performance and efficiency is great airflow throughout. Intake flow was improved over previous
engines by straightening out and optimizing the flow path from the intake manifold into the
cylinder heads, while the exhaust ports are also designed for greater flow. The engine’s
efficiency also optimizes emissions performance.
The 5.3L is powerful, but delivers exceptional refinement to go with great strength. Quiet
features built into the engine are complemented by an improved engine cradle and mounting
system. These help reduce vibrations transmitted through the chassis and into the passenger
compartment.
Gen IV Cylinder Block and Rotating Assembly
The LMG 5.3L’s Gen IV iron cylinder block shares two key design elements with GM’s original
small-block V-8: a 90-degree cylinder angle and 4.400-inch bore centers. The Gen IV block was
developed with math-based tools and data acquired in GM’s racing programs, and provides a
light, rigid foundation for an impressively smooth engine. Its deep-skirt design helps maximize
strength and minimize vibration. The bulkheads accommodate six-bolt, cross-bolted mainbearing caps that limit crank flex and stiffen the engine’s structure. A structural oil pan further
stiffens the powertrain.
Along with the rigid block, the engine’s rotating assembly was designed for optimal strength and
duration complemented by features designed to make the LMG quiet and smooth. Examples
include pistons with “floating” wrist pins, which reduce stress on the piston pin. The pin connects
the piston to the connecting rod and the floating design allows tighter tolerances and reduces
noise generated as the piston moves through the cylinder.
To further reduce wear, the pistons are coated with a polymer material that limits bore scuffing,
or abrasion of the cylinder wall over time from the piston's up-down motion. The polymer coating
also dampens noise generated by the piston's movement. The result for the customer is less
engine wear, improved durability and quieter operation.
The 5.3L also features a heavy-duty timing chain developed expressly for quiet operation. The
chain, which connects the camshaft and crankshaft, is validated for 200,000 miles (320,000 km)
of operation and fitted with a leaf-spring-type dampener. Even the most durable chains stretch
with time. In many engines they must be adjusted or replaced at scheduled intervals. The 5.3L’s
chain dampener maintains optimal chain tension for the life of the engine and eliminates any
flapping motion that might develop as the chain stretches with mileage. It ensures that the
timing chain operates as smoothly and quietly as new, even as the engine accumulates high
mileage.
High-Flow Cylinder Heads and Valvetrain
The 5.3L’s cylinder heads feature “cathedral”-shaped intake ports that promote exceptional
airflow. They’re derived from the high-performance LS6 cylinder heads used on the “C5”
Chevrolet Corvette Z06. They support great airflow at higher rpm for a broader horsepower
band, along with strong, low-rpm torque.
Large, 2.000-inch intake and 1.550-inch exhaust valves are used in the 356-T6 aluminum alloy
heads, but are made of specific material that supports the load and durability requirements of a
truck engine. The intake ports that feed the combustion chambers, as well as the D-shaped
exhaust ports, are designed for excellent high-rpm airflow.
Camshaft Phasing
The 5.3L features variable valve timing, maximizing engine performance for given demands and
conditions. At idle, for example, the cam is at the full advanced position, allowing exceptionally
smooth idling. Under other conditions, the phaser adjusts to deliver optimal valve timing for
performance, driveability and fuel economy. At high rpm it may retard timing to maximize airflow
through the engine and increase horsepower. At low rpm it can advance timing to increase
torque. Under light loads, it can retard timing at all engine speeds to improve fuel economy.
A vane-type phaser is installed on the cam sprocket to turn the camshaft relative to the
sprocket, thereby adjusting the timing of valve operation on the fly. It is a dual-equal cam
phasing system that adjusts camshaft timing at the same rate for both intake and exhaust
valves. The system allows linear delivery of torque, with near-peak levels over a broad rpm
range, and high specific output (horsepower per liter of displacement) without sacrificing overall
engine response, or driveability. It also provides another effective tool for controlling exhaust
emissions. Because it manages valve overlap at optimum levels, it eliminates the need for an
Exhaust Gas Recirculation (EGR) system.
The vane phaser is actuated by hydraulic pressure from engine oil, and managed by a solenoid
that controls oil pressure on the phaser. The phaser uses a wheel or rotor with four vanes (like a
propeller) to turn the camshaft relative to the cam sprocket, which turns at a fixed rate via chain
from the crankshaft. The solenoid directs oil to pressure points on either side of the four phaser
vanes; the vanes, and camshaft, turn in the direction of the oil flow. The more pressure, the
more the phaser and camshaft turn. The dual-equal phaser system has the authority to retard
the cam timing by up to 52 crankshaft degrees.
E85 Flex-Fuel Capability
E85 is a clean-burning, domestically produced fuel composed of 85 percent ethanol alcohol and
15 percent gasoline. Ethanol is renewable and produces fewer greenhouse gases in the
combustion process. It can be produced from various feed stocks, including corn and wheat
stalks, forestry and agricultural waste and even municipal waste.
The LMG’s flex-fuel technology is both sophisticated and durable. Hardware changes are limited
to the injectors with a higher maximum flow rating. Because ethanol has less energy than the
same volume of gasoline, more fuel is required to produce the same horsepower at wide-open
throttle.
A special fuel sensor is not required for the LMG engine; it uses a “virtual sensor” within the
Engine Control Module that takes readings from the oxygen sensors, fuel level sensor and
vehicle speed sensors to adjust the length of time the fuel injectors open for the type of fuel
used.
Active Fuel Management
GM's Active Fuel Management technology increases fuel economy approximately 6 percent
under the federal government's required testing procedure and potentially more in certain realworld driving conditions. AFM temporarily deactivates four of the LMG’s cylinders under light
load conditions and seamlessly reactivates them when the driver demands full power. The
transition takes less than 20 milliseconds, and is virtually indiscernible to most drivers.
AFM is managed by the engine control module (ECM). When conditions are optimal, it
automatically shuts down every second cylinder, according to firing order, during light-load
operation. In engineering terms, this allows the working cylinders to achieve better thermal,
volumetric and mechanical efficiency and lowering cyclical combustion variation from cylinder to
cylinder. As a result, AFM delivers better fuel economy and lower operating costs. The only
mechanical components required are special valve lifters for cylinders that are deactivated, and
their control system. Active Fuel Management relies on three primary components: De-ac (for
deactivation) or collapsible valve lifters, a Lifter Oil Manifold Assembly (LOMA), and the ECM.
The LMG’s fuel injectors are identical for all cylinders; those feeding the deactivated cylinders
are simply shut down electrically by the ECM during deactivation. When the cylinders are
deactivated, the engine effectively operates as a V-4. Also, the exhaust system for the LMG is
carefully tuned to maintain optimal noise and vibration control. In four-cylinder operation, the
engine creates second-order exhaust pulses; in eight-cylinder operation, it creates fourth-order
exhaust pulses. The system requires special pipe tuning to account for both.
Advanced Electronic Throttle Control
GM has led the industry in applying electronic throttle control (ETC). With ETC, there is no
mechanical link between the accelerator pedal and the throttle body. A sensor at the pedal
measures pedal angle and sends a signal to the engine control module (ECM), which in turn
directs an electric motor to open the throttle at the appropriate rate and angle. ETC delivers a
number of benefits to the customer.
Returnless Fuel Injection
The LMG is equipped with a “returnless” fuel injection system, also known as a demand system,
that helps optimize performance and emissions. It delivers only the amount of fuel needed by
the injectors, and returns no fuel to the gas tank, which essentially eliminates heat transfer from
the engine to tank. This reduces the amount of vapor generated in the tank and captured by the
vehicle's Onboard Refueling Vapor Recovery (ORVR) system.
Quiet Exhaust Manifolds
The exhaust manifolds were developed to improve durability and sealing and reduce operational
noise. Cast nodular iron was the material of choice for its basic durability and excellent heat
management properties. The manifolds feature saw cuts along their cylinder head mounting
flange. Originally developed for the big-block Vortec 8.1L, these cuts split the flange into three
separate sections, allowing each section to move under extreme hot-cold temperature
fluctuations without interacting with, or creating stress on, another section. The cuts virtually
eliminate friction on and movement of the exhaust manifold gaskets, helping ensure proper
sealing for the life of the engine and reducing the chance of gasket failure.
The exhaust manifolds are fitted with new triple-layer heat shields fabricated from stainless steel
and insulating material. The shields limit heat transfer from the engine to the engine bay,
allowing the 5.3L to reach optimal operating temperature more quickly, yet reducing heat in the
engine compartment once that temperature is achieved. They also dampen the sound of
exhaust gas rushing through the manifolds and further reduce the amount of engine operational
noise that finds its way into the vehicle interior.
58X Ignition System
The LMG has an advanced 58X crankshaft position encoder to ensure that ignition timing is
accurate throughout its operating range. The 58X crankshaft ring and sensor provide more
immediate, accurate information on the crankshaft’s position during rotation. This allows the
engine control module to adjust ignition timing with greater precision, which optimizes
performance and economy. Engine starting is also more consistent in all operating conditions.
In conjunction with 58X crankshaft timing, the LMG applies the latest digital cam-timing
technology. The cam sensor is located in the front engine cover, and it reads a 4X sensor target
on the cam sprocket. The target ring has four equally spaced segments that communicate the
camshaft’s position more quickly and accurately than previous systems with a single segment.
The dual 58X/4X measurement ensures extremely accurate timing for the life of the engine.
Moreover, it provides an effective backup system in the event one sensor fails.
Additional Details
Ignition modules: The Vortec 5.3L’s individual coil-near-plug ignition features advanced coils
that are compact and mounted on the rocker covers. An individual coil for each spark plug
delivers maximum voltage and consistent spark density, with no variation between cylinders.
Iridium-tip spark plugs: The spark plugs have an iridium electrode tip and an iridium core in
the conductor, offering higher internal resistance while maintaining optimal spark density over its
useful life. Its “self-cleaning” properties are improved, decreasing potential for plug fouling and
further reducing the likelihood of maintenance over the 100,000-mile plug life. The electrode
design improves combustion efficiency for maximum fuel economy and minimum emissions.
Accessory drive: A low-modulus air conditioning compressor belt is used to eliminate the need
for a separate belt tensioner, further simplifying the engine’s design and reducing mass.
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