2008 GM 3.9L V6 (LGD, LZ9, LZ8)
3.9L V6 ( LGD, LZ9, LZG ) CAR AND TRUCK ENGINE
2008 Model Year Summary
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New RPO for 2008 Chevrolet Impala (LZG)
E85 Flexible-Fuel Capability with Active Fuel Management (LZG)
E85 Flexible-Fuel Capability (LGD)
Full Description of New and Update Features
New RPO for the 2008 Chevrolet Impala (LZG)
GM Powertrain’s new-generation 60-degree 3.9L V6 is now available with Active Fuel
Management cylinder-deactivation technology combined with E85 flex-fuel capability and
Variable Valve Timing (LZG). RPO LZG is optional in Impala. RPO (LGD) is optional in
Chevrolet Uplander and Pontiac Montana SV6 and features Variable Valve Timing and E85
flex-fuel capability. RPO (LZ9) also with Variable Valve Timing, is offered for 2008 in the Pontiac
G6, Pontiac Montana SV6, and Chevrolet Uplander. In all applications, the 3.9L V6 is installed
with GM Powertrain’s Hydra-Matic 4T65 four-speed automatic transmission.
Active Fuel Management (LZG)
The 3.9L is the first GM V6 in North America equipped with GM’s industry exclusive Active Fuel
Management (AFM) technology. (GM has a 3.0L V6 with AFM in China in the Buick LaCrosse.
It is similar in concept and execution to AFM introduced on the Gen IV small-block V8s, tuned
specifically for a six-cylinder engine.
Active Fuel Management temporarily de-activates three of the 3.9L’s cylinders under light load
conditions. It should increases fuel economy measurably under the federal government’s
required testing procedure, and potentially more in certain real-world driving conditions. Yet
vehicle owners don’t have to compromise on the 3.9Ls outstanding balance of power and torque
to go farther on a tank of gas.
AFM stems from a simple premise: many drivers have more power than they need much of the
time. Many choose powerful engines for their potential for exhilarating acceleration, or good
performance at full load. Yet during routine commuting that powerful engine operates at a
fraction of its capability. Volumetric efficiency is impaired, and that means less than optimal fuel
mileage. AFM offers a common-sense solution. It saves fuel by using only half of the 3.9Ls
cylinders during some driving conditions, and seamlessly reactivates the other cylinders when a
driver demands full power for acceleration.
Managed by the new E38 engine control module (ECM), AFM 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 by
reducing heat loss, combustion loss and friction, and lowering cyclical combustion variation from
cylinder to cylinder. As a result, AFM delivers better fuel economy and lower operating costs.
Perhaps the most sensible thing about AFM is that it harnesses the engine’s existing
capabilities, starting with the potential designed into the E38 ECM. The only mechanical
components required are special valve lifters for cylinders that are deactivated, and their control
system. The incremental cost for the customer is nominal per engine. 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.
One of the most sophisticated engine controllers, the E38 ECM (below) measures load
conditions based on inputs from vehicle sensors and interprets that information to mange more
than 100 engine operations, from fuel injection to spark control to electronic throttle control.
AFM adds an algorithm to the engine control software to manage cylinder deactivation and
reactivation. When loads are light, the E38 automatically closes both intake and exhaust valves
for half of the cylinders and cuts fuel delivery to those three. The valves re-open to activate all
cylinders when the driver demands brisk acceleration or full torque. The engine’s electronic
throttle control (ETC) is used to balance torque following cylinder deactivation or reactivation.
The transition takes less than 20 milliseconds, and can’t be detected by the driver.
Valve lifters are operated by the engine’s camshaft, and lift a pushrod that operates the valves
in the cylinder head. In the 3.9L, the De-ac lifters are installed in cylinders 1, 3, and 5, while
the remaining cylinders use conventional lifters. The hydraulically operated De-ac lifters have a
spring-loaded locking pin actuated by oil pressure. For deactivation, hydraulic pressure
dislodges the locking pin, collapsing the top portion of the lifter into the bottom and removing
contact with the pushrod. The bottom of each De-Ac lifter rides up and down on the cam lobe
but the top does not move the push rod. The valves do not operate and combustion in that
cylinder stops. During reactivation, the oil pressure is removed, and the lifter locks at full length.
The pushrods, and therefore the valves, operate normally.
The final AFM component is the LOMA. This cast-aluminum assembly is installed in the 3.9L’s
V, or valley, in place of a conventional engine block cover. The LOMA holds three solenoids,
control wiring and cast-in oil passages. The solenoids are managed by the ECM, and each one
controls oil flow to a De-Ac Lifter, activating and de-activating the valves at one cylinder as
required for Active Fuel Management.
The 3.9L V6’s fuel injectors are identical for all cylinders; those feeding the de-activated
cylinders are simply shut down electrically by the ECM during de-activation. When the cylinders
are deactivated, the engine effectively operates with three cylinders. AFM operation is load
based, as measured by the ECM using dozens of inputs, overlain with the driver’s demand for
power as measured by throttle application. AFM’s response time varies with oil temperature, but
in all cases is measured in milliseconds. Operation is always transparent to the driver. The
engine returns to V6 mode the instant the controller determines that acceleration or load
requires additional power.
The benefits are substantial. Active Fuel Management does not effect exhaust emissions, and it
will reduce overall emissions significantly to the extent that less fuel is used. Further, the
savings reflected in EPA numbers may not account for AFM’s full impact. Owners who primarily
travel long distances at steady speeds will see substantially greater fuel-economy
improvements.
Active Fuel Management required fine-tuning for the 3.9L V6 to maintain excellent noise and
vibration control in both three and six-cylinder mode. Because AFM activates and de-activates
cylinders according to firing order, it works on cylinders in the 3.9L’s left bank. In fuel-saving
mode, the 3.9L effectively operates as an inline 3. This creates more slack in the accessory
drive belt. The alternator is therefore equipped with a unique de-coupling clutch that seamlessly
tensions the belt as the engine switches between modes. And because the engine generates
different exhaust-pulse frequencies in three- and six-cylinder modes, the exhaust system is
tuned for the same smooth, quiet operation in both. ,
The 3.9L’s exclusive cam-in-block VVT technology works synergistically with Active Fuel
Management and helps maximize AFM’s fuel saving potential. The cam phaser can adjust
valve-timing for maximum torque when the 3.9L is operating as a three-cylinder, keeping the
engine in this fuel-saving mode as long as possible.
E85 Flexible-Fuel Capability (LGD, LZG)
GM has led the industry in introducing flex-fuel capability to its cars and trucks, and the flex-fuel
capable 3.9L V6 (RPO’s LGD and LZG) extends availability to an even broader range of
customers. E85 is a clean-burning alternative fuel made in the United States from corn and
other crops, composed of 85 percent ethanol alcohol and 15 percent gasoline. The 3.9L’s
flex-fuel technology is both sophisticated and durable.
The first flex-fuel engines required special valves and valve seats to withstand the corrosive
effects of ethanol. Not the 3.9L V6. The Silcrome 1 valves used in all variants are up to the
challenge. Compared to conventional iron-alloy valve material, Silcrome 1 includes tungsten,
vanadium, manganese, silicone and higher chromium content. It is harder, and it improves
durability, even under the rigors of ethanol operation.
Hardware changes for flex-fuel operation are limited to the injectors. Because ethanol has fewer
BTUs (less energy) than the same volume of gasoline, more fuel is required to produce the
same horsepower at wide-open throttle. Flex fuel engines use unique injectors with a
diamond-like finish, greater cone angle and higher maximum fuel-flow rate. The fuel rail
matches the injectors, but it’s manufactured of the same stainless steel used for all 3.9L V6 fuel
rails.
The flex-fuel 3.9L doesn’t require a special fuel sensor. The first flex-fuel engines used a
light-reactive sensor to measure fuel composition from 100 percent gasoline to 85 percent
ethanol. The 3.9L has a virtual sensor—software programmed in the E38 ECM with no separate
physical sensor whatsoever. Based on readings from the oxygen (O²) sensors, fuel level sensor
and vehicle speed sensors, the ECM adjusts the length of time the fuel injectors open for the
type of fuel used. Within a few miles after filling up, the E38 controller determines what fuel is
powering the 3.9L V6 and manages the engine accordingly.
E85 fuel provides an environmentally friendly companion or alternative to gasoline. It is
biodegradable and doesn’t contaminate the water supply. Ethanol can be produced from various
feed stocks, including corn and wheat stalks, forestry and agricultural waste, and even
municipal waste.
Advanced Engine Control Modules
Every 3.9L V6 is managed by one of the three controllers in GM Powertrain’s new family of
engine control modules (ECM), which will direct nearly all engines in Powertrain’s line-up. These
ECMs more precisely orchestrate the myriad operations that occur within the 3.9L every split
second. In combination with advanced sensor technology, they include the ability to control and
synchronize systems such as Active Fuel Management and cam-in-block variable valve timing.
Most 3.9Ls use the mid-line controller, know as the E38. The 3.9Ls built for the Buick Terazza,
Chevrolet Uplander, Pontiac Montana SV6 and Saturn Relay are equipped with the high-line
E67 ECM.
These ECMs feature 32-bit processing, compared to the conventional 16-bit processing in
previous 60-degree V6 engines. They operate at 59 MHz, with 32 megabytes of flash memory,
128 kilobytes of RAM and a high-speed CAN bus, and the synchronizes more than 100
functions, from spark timing to cruise control operation to traction control calculations. The E38
works roughly 50 times faster than the first computers used on internal combustion engines in
the late 1970s, which managed five or six functions.
The family strategy behind GM’s new ECMs allows engineers to apply standard manufacturing
and service procedures to all powertrains, and quickly upgrade certain engine technologies
while leaving others alone. It creates both assembly and procurement efficiencies, as well as
volume sourcing. In short, it creates a solid, flexible, efficient engine-control foundation, allowing
engineers to focus on innovations and get them to market more quickly. The family of controllers
means the ECM and corresponding connectors can be packaged and mounted identically in
virtually every GM vehicle. Powertrain creates all the software for the three ECMs, which share
a common language and hardware interface that’s tailored to each vehicle.
The new ECMs also apply a new, rate-based monitoring protocol sometimes known as
run-at-rate diagnostics. Rate-based diagnostics improve the robustness of the Onboard
Diagnostics System (OBD II) and ensure optimal performance of emissions control systems.
The new software increases the frequency at which the ECM checks various 3.9L systems, and
particularly emissions-control systems such as the catalytic converter and oxygen sensors.
Rate-based diagnostics more reliably monitor real-word operation of these systems, and allow
regulatory agencies to more easily measure and certify emissions compliance.
Overview
GM Powertrain’s new overhead-valve V6 engines demonstrate conclusively that the inherent
strengths of cam-in-block design can be applied in the environmentally sensitive 21st century--in
trucks and cars. With advanced technologies such as Active Fuel Management and variable
vale timing, the 3.9L delivers the power and flexibility of a large-displacement V6 with new levels
of fuel efficiency. It brings innovation to the mainstream, with wide application in a high-value
package the typical consumer can afford.
This new generation V6 allows a high level of flexibility, with common castings over a range of
displacements. The 3.9L V6 shares its block, pistons and cylinder heads with Powertrain’s new
3.5L (RPOs LZ4 and LZE). A common bore measures 99 mm; displacement is increased in the
3.9L with a longer stroke (84 mm, compared to 76 mm for the 3.5L). The two engines share 80
percent of their parts.
Thanks to its relatively narrow 60-degree block angle, the 3.9L V6 is compact, giving vehicles
teams more latitude with platform design and styling. More importantly, the 60-degree
configuration is inherently balanced, ensuring powertrain smoothness without the additional cost
of balance shafts. The new 3.9L V6 differs from previous GM 60-degree designs in its offset
cylinder bores. The centerlines through the bores on each bank do not intersect at the crank
axis; rather, they intersect 3 mm below the crank axis. The offset bores present a number of
advantages, including room for larger cam journals and flexibility to stroke the engine for more
displacement. The 3.9L block also features a unique “U-flow” coolant path. The coolant
passages flow coolant in a specific, predetermined path, starting at the front of block, then
rearward toward transmission, up through the cylinder heads and back to the front. The
thermostat is placed near the inlet from the radiator, decreasing warm-up time. The fill point is at
the highest point of the cooling system to prevent air pockets in the hoses or passages.
The cylinder heads apply design features developed for the high-output LS1 and LS6 Corvette
small-block V8s. The 3.9L V6’s valves are similar to those in the LS1, as is its combustion
chamber design. Low-friction hydraulic roller lifters work the valves, improving the engine’s
efficiency and reducing vibration.
Before introduction of the 3.9LV6, variable intake manifolds were not a familiar feature on
overhead-valve V6 engines, The 3.9L V6’s two-piece cast aluminum manifold has a valve in its
plenum to optimize air intake for the desired performance parameters, eliminating the
compromise required with a fixed-flow intake manifold. At low engine speeds, the engine control
module (ECM) closes the valve to create a longer intake path, improving combustion efficiency
and increasing torque. At higher engine speeds, it opens the valve, shortening the path for free
breathing and maximum horsepower. The 3.9L also applies the latest electronic throttle control
(ETC) technology, streamlining the system by eliminating a separate throttle actuator control
(TAC) module. The ECM controls the throttle motor directly. The direct link improves throttle
response time (albeit in millisecond increments that are not apparent to the driver) and improves
system security by removing a device (the TAC) the must be monitored for malfunction.
The 3.9L V6’s “returnless” fuel injection system is the new standard at GM. It eliminates fuel
return lines between the engine and the gasoline tank, essentially eliminating heat transfer from
the engine to the tank and reducing the amount of vapor emissions substantially. New
generation fuel injectors with shrouded nozzles are designed to minimize clogging and maintain
optimal performance when in high heat.
For all the advanced systems in the 3.9L V6, perhaps the most significant—certainly the one
that has garnered the most attention—is variable valve timing (VVT). GM’s new generation V6s
were the first cam-in-block engines with VVT—an accomplishment engineers considered
extremely difficult, if not impossible, just a few years ago. The 3.9L’s dual-equal VVT uses a
hydraulically operated vane-type cam phaser that turns the camshaft relative to its drive
sprocket.
The advantages of cam-in-block VVT are pronounced. The cam phaser changes valve timing
on the fly, maximizing engine performance for given demands and conditions. At idle, for
example, the cam is at the full advanced position. That allows exceptionally smooth idling.
Under other operating demands, the phaser adjusts to deliver optimal valve timing for
performance, drivability and fuel economy. At high rpm it might retard timing to maximize airflow
through the engine and increase horsepower. At low rpm it advances timing to increase torque.
Under a light load (say, casual everyday driving), it can retard timing at all engine speeds to
improve fuel economy. Without cam phasing, a cam design must be biased toward one
strength or another—high-end horsepower or low-end torque, for example—or profiled at some
median level that maximizes neither.
Variable valve timing 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 drivability. 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.
Virtually every component and system in GM’s new generation cam-in-block V6s was reviewed
in an effort to enhance durability and reduce noise, vibration and harshness. Piston-cooling jets
remain the exception rather than the rule in overhead cam engines, yet each piston in the 3.9L
V6 has its own pressure-actuated jet that sprays oil toward its skirt, coating its underside and
the cylinder wall with an additional layer of lubricant. The extra lubrication cools the pistons,
reducing both friction and operational noise and helping ensure durability. The cam-drive chain
has a leaf spring-type dampener that 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.
Multi-layer steel gaskets are sandwiched between the block and cylinder heads to maintain
optimal sealing for the life of the engine. The cast-iron exhaust manifolds are fitted with heat
shields fabricated from stainless steel and insulating material. These limit heat transfer from the
engine to the engine bay, allowing the 3.9L 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. A cast aluminum
oil pan increases engine rigidity and radiates less noise than a conventional steel pan. An
acoustic engine cover further reduces the amount of noise transmitted to the passenger
compartment from the engine.
Low maintenance was a development priority. The spark plugs have an iridium tip and core to
maintain spark density over their 100,000-mile life, helping ensure the same fuel efficiency and
emissions performance over the last 10,000 miles as the first. The coolant and accessory belt
are both expected to last 100,000 miles. Maintenance in typical use is limited to oil changes,
and even those are made as simple as possible. The GM Oil Life System measures how hard
the engine is used and calculates the optimal life expectancy of the engine oil, indicating an oil
change when it’s actually needed, rather than according to some predetermined mileage
interval.
GM’s new overhead-valve V6 engines define the concept of high value in powertrain
development. The deliver advanced, industry exclusive technologies with real benefit for
customers, yet they keep both the cost of production and the cost of ownership low. In short,
the new 3.9L V6 delivers a top-shelf balance of good specific output, low-end response, even
torque delivery, low maintenance and value, with vehicle packaging flexibility in a wide range of
front and all-wheel drive applications.