A new generation of GM’s legendary small-block V-8 engine is the power behind GM’s all-new full-size SUVs, delivering increased performance and fuel economy through advanced technology such as Displacement On Demand and variable valve timing.
The Gen IV small-block Vortec V-8 engine family – including the 5.3L V-8 – is standard in all models, with displacements ranging from 4.8L to 6.2L, and estimated horsepower ranging from 290 horsepower (216 kw) to 400 horsepower (298 kw).* The engines are backed by proven Hydra-Matic electronically controlled automatic transmissions, including a new 6L80 six-speed.
The new Vortec engines represent the fourth generation of the small-block V-8, which debuted in 1955. Highlights include:
- Revised cylinder block design with externally mounted knock sensors
- High flow cylinder heads on 6.0L and 6.2L engines
- Variable valve timing on 6.0L and 6.2L engines
- Displacement On Demand on 5.3L and aluminum-block 6.0L engines
- Electronic throttle control
- 58X ignition system
- New, more powerful E38 32-bit controller
- Enhanced quietness and smoothness
- Returnless fuel system
- E85 fuel capability on some 5.3L engines
- Stringent validation and durability testing throughout development process
“The Vortec Gen IV V-8 family delivers balanced performance and efficiency through technical innovation,” said Christopher Meagher, assistant chief engineer. “Fuel-saving features, such as Displacement On Demand, affirms the small-block V-8’s leadership role in trucks.”
Supporting the high-performance capability of the 6.2L engine is the new Hydra-Matic 6L80 six-speed automatic transmission. It has a wide, 6.04:1 overall ratio – including two overdrive gears – that helps deliver an excellent balance of performance and fuel economy. It is similar to the six-speed “paddle shift” automatic transmission introduced on the 2006 Corvette, but is been tailored for the heavy-duty requirements of SUVs and trucks.
“There are no compromises with the 6L80 transmission – it delivers great performance and enables improved fuel economy on the highway, all with smooth, almost imperceptible operation,” said Jeff Baran, chief engineer for six-speed rear-wheel drive transmissions.
The 6L80’s six forward gears have smaller “steps” between them, compared to a conventional four-speed automatic, which bolsters both performance and the feeling of smoothness. Shorter steps between the gears help the transmission quickly find the best gear for the vehicle speed and road conditions, with less back-and-forth hunting on grades – a trait that is particularly helpful when towing.
Gen IV small-block details
The Gen IV Vortec V-8 truck engines are built in a variety displacement and power combinations, including versions with aluminum cylinder blocks. All engines share a basic architecture that includes 4.400-inch bore centers – the same design foundation on which the original small-block V-8 was developed in the early 1950s. Initial Gen IV engine offerings include:
- 4.8L iron block (RPO LY2), rated at 290 horsepower (216 kw)*
- 5.3L iron block (RPO LY5) with Displacement On Demand technology, rated at 320 horsepower (238 kw)* – including E85-capable version (RPO LMG)
- 5.3L aluminum block (RPO LC9) with Displacement On Demand technology and E85 capability, rated at 320 horsepower (238 kw)*
- 6.0L iron block (LY6) heavy-duty engine with variable valve timing, rated at 350 horsepower (261 kw)*
- 6.0L aluminum block (L76) with Displacement On Demand technology and variable valve timing, rated at 355 horsepower (264 kw)*
- 6.2L aluminum block (L92) with variable valve timing, capable of 380 to 400 horsepower (283 to 298 kw)*
All Gen IV Vortec engines are designed to provide improved fuel economy and reduced emissions, compared to previous-generation small-block V-8s. The 5.3L engines with Displacement On Demand (DOD) technology, for example, provide up to seven percent fuel economy gains.
The new engines also meet more stringent emissions standards. In fact, compared to truck engines of a decade ago, the Gen IV Vortec engine family is approximately 90 percent cleaner. Cast iron exhaust manifolds matched with dual close-coupled catalytic converters help reduce cold-start emissions, which is the largest source of vehicle emissions.
Revised cylinder block
Aluminum-block Gen IV-design engines debuted as the LS2 in the 2005 Chevy Corvette and SSR, as well as the ’05 Pontiac GTO. The new Vortec truck engines share the basic design of these versions, but are engineered for the specialized needs of truck applications. Like the LS2, the new Vortec engines have a revised cylinder block design that features new, externally mounted knock sensors. They were moved from the valley area to enable Displacement On Demand technology and other advanced systems.
Some Gen IV Vortec engines use aluminum cylinder blocks, which offer reduced mass – an attribute that supports improved vehicle weight distribution and slightly improved fuel economy. The aluminum blocks are virtually identical to their iron counterparts, including a deep skirt design that incorporates cross-bolted main bearing caps and a structural oil pan. All engines, except the 6.2L L92, use a proven iron crankshaft design and highly durable reciprocating components. The high-performance 6.2L L92 uses a forged steel crankshaft.
The block for the 6.2L engine features a crankcase “windows” – vents that help improve bay-to-bay breathing. This reduces pumping losses and supports the high horsepower output of the high-performance engine. A new, 58X ignition system and a more powerful, E38 ECM are integrated on all engines.
The 58X ignition system uses a unique crankshaft wheel and sensors to provide the new, 32-bit E38 ECM with more immediate information on the crankshaft’s position during rotation. In turn, this allows the controller to adjust ignition timing with greater precision, which optimizes performance and economy. Engine starting also is more consistent.
Displacement On Demand
Some 5.3L and 6.0L engines are equipped with GM’s fuel-saving Displacement On Demand technology, which can temporarily shut down the combustion process of half the engine’s cylinders under certain driving conditions to save fuel. GM was the first manufacturer to offer this fuel-saving technology on trucks. On the new full-size SUVs, it works with other attributes, such as improved vehicle aerodynamics, to maintain GM’s fuel economy leadership in the segment.
A sophisticated engine controller determines when to deactivate cylinders, allowing the engine to maintain vehicle speed in lighter-load conditions such as highway cruising. The process is seamless and virtually imperceptible. When the cylinders are deactivated the engine effectively operates as a V-4, with alternate cylinders on each cylinder bank disabled. The engine returns to V-8 mode the instant the controller determines the vehicle speed or load requires additional power. The key to DOD’s efficiency and virtually imperceptible operation is a set of special two-stage hydraulic valve lifters, which allows the lifters of deactivated cylinders to operate without actuating the valves.
The valve lifters have inner and outer bodies, which normally operate as a single unit. When the engine controller determines cylinder deactivation conditions are optimal, the outer body moves independently of the inner body on the disabled cylinders’ lifters. The outer body moves in conjunction with camshaft actuation, but the inner body does not move, holding the pushrod in place. This prevents the pushrod from actuating the valve, thereby halting the combustion process. Solenoids in the engine lifter valley operate to deliver high-pressure oil to the switching lifters, activating a release pin to separate the inner and outer bodies. Oil circulation and pressure do not vary, regardless of the engine’s operational mode. Lifter design and pushrod length are the same for every cylinder, but camshaft lobe profiles differ for cylinders designated to be deactivated.
The engine’s electronic throttle control (ETC) also is used to increase manifold pressure in V-4 mode so that the engine can maintain a V-8 torque load.
Variable valve timing
Variable valve timing (VVT) is a standard feature on 6.0L and 6.2L engines; it helps optimize camshaft timing to improve low-rpm torque and high-rpm horsepower. The introduction of variable valve timing through the unique dual-equal cam phaser is the industry’s first application of VVT on a mass-produced V-8 cam-in-block engine. The unique dual-equal phaser adjusts the camshaft timing at the same rate for both the intake and exhaust valves.
The system incorporates a vane-type camshaft phaser that changes the angular orientation of the camshaft, thereby adjusting the timing of the intake and exhaust valves to optimize performance and economy, and help lower emissions. It offers infinitely variable valve timing in relation to the crankshaft. The cam phaser vane is attached to the camshaft on the front journal. As driving conditions warrant, the cam phaser system can reduce ignition timing at higher rpm levels to increase power. At lower rpm levels, torque is enhanced with increased timing.
This cam phaser feature was pioneered by GM and introduced on the new 3.5L and 3.9L V-6 engines in 2005 – a first for the use of variable valve timing on a cam-in-block engine design. As driving conditions warrant, the cam phasing system can reduce ignition timing at higher rpm levels to increase power. At lower rpm levels, torque is enhanced with increased timing.
Precise camshaft timing is the key to the variable valve timing system’s capability to optimize performance. Like the 58X ignition system, cam phasing is directed by the E38 ECM. It relies on data from a camshaft position sensor – a target ring with four equally spaced segments – that communicates the camshaft’s position quicker and more accurately than previous systems that used just a single segment. Also, a leaf spring-type tensioner is used on the timing chain to ensure precise tension.
The aluminum-block 6.0L version uses variable valve timing in conjunction with Displacement On Demand technology to bolster fuel economy. With cam phasing, Displacement On Demand technology allows the engine to run longer in fuel-saving four-cylinder mode, while producing instant V-8 power and response as soon as the driver calls for it.
High-flow cylinder heads
The Vortec 6.0L and 6.2L engines offer a significant power level increase compared with previous premium engines, with much of the newfound power coming from high-flow aluminum cylinder heads. The heads are based on the racing-derived cylinder heads of the Corvette Z06’s LS7 7.0L engine, including a unique inlet port shape and offset rocker arm design. Airflow of the heads is supported by large 55-mm-diameter intake valves and 40.4-mm-diamter exhaust valves.
“The heads use the high-performance technology of the Corvette’s LS7 to build efficient power in truck engines,” said Meagher.
Vortec 4.8L and 5.3L engines also have high-flow, Corvette-derived heads. They are based on the previous-generation Corvette Z06’s LS6 engine’s cylinder heads and have flow characteristics commensurate with the engines’ airflow-to-displacement needs. All the Gen IV Vortec engine variants use the same efficient ignition coil packs of the LS2 to light off the air/fuel mixtures that are drawn through the heads.
Quiet, durable operation
All Gen IV small-block Vortec V-8 engines are designed for quieter operation, including:
- Special friction-reducing coating on piston skirts
- Full floating piston pins
- Damping patch on the oil pan (externally mounted)
- Timing chain tensioner
- Quieter alternator
The quiet features of the engines are complemented in the vehicles with stronger engine cradles and mounting systems. These systems help reduce vibrations transmitted through the chassis and would otherwise be felt by vehicle passengers.
Backing the new engines’ quietness is the assurance of long-lasting performance. The new Gen IV engines were validated under extreme conditions, with dynamometer testing equivalent to 150,000 miles. The Vortec 6.0L iron block heavy-duty engine was tested the equivalent of 200,000 miles.
Some of the stringent durability testing included cycling engines between the peak torque and peak horsepower rpm points – the equivalent of towing a heavy trailer up a steep grade – for 600 straight hours.
The engines also feature many long-life engine components that can reduce maintenance intervals and costs. The iridium-tip spark plugs, engine coolant, accessory drive belt and sealing gaskets are some of these items. Also, a revised water pump design (introduced on late Gen III V-8s) has improved sealing for increased durability.
E85 capability
Two versions of the Vortec 5.3L Gen IV V-8 are compatible with E85 ethanol-based fuel, which offers a good environmental alternative to gasoline. The engines can run on any combination of gasoline and/or E85 fuel.
A new virtual fuel sensor reduces the cost and complexity of adding E85 capability to the fuel system. The ECM samples the exhaust at the oxygen sensor, and an algorithm determines whether E85 is used, as well as its mixture percentage with gasoline. It’s a much simpler, less costly system than previous systems that relied on fuel composition sensors. In fact, the entire system on the engine is simple: only the fuel rail and fuel injectors are different between E85 versions and non-E85 versions.
E85 is a clean-burning alternative fuel made in the United States with homegrown corn and other crops. E85 is largely alcohol, composed of 85 percent ethanol and 15 percent gasoline. The alcohol is produced by fermenting plant sugars. E85 nearly eliminates greenhouse gas emissions from automobiles, is biodegradable, doesn’t contaminate the water supply and can be produced from various feed stocks, including grain, corn and wheat stalks, forestry and agricultural waste, and even municipal waste.
Hydra-Matic 6L80 details
GM’s new, Hydra-Matic 6L80 electronically controlled six-speed automatic transmission is matched with the 6.2L engine. A higher-capacity Hydra-Matic 4L70-E four-speed automatic is paired with 6.0L engines; 4.8L and 5.3L powertrains are teamed with the Hydra-Matic 4L60-E four-speed.
The 6L80’s wide, 6.04:1 overall ratio, including two overdrive gears, allows for the transmission’s shorter steps between gears. This enables a steep, 4.02:1 first gear, which provides a very strong launch feel. The two overdrive gears include a 0.85:1 ratio in fifth gear and a 0.67:1 ratio in sixth. With two overdrive gears, engine rpm is reduced by approximately 9 percent at 60 mph – a reduction of about 1,350 rpm. Lower engine rpm can bolster fuel economy because less fuel is used. A lower-rpm cruising speed also enhances smoothness and reduces noise heard in the vehicle’s cabin.
Technical sophistication is exemplified by clutch to clutch operation that reduces complexity and packaging. It also enhances the performance feel of the transmission, as shifts feel more immediate and precise. Clutch to clutch operation is achieved with three planetary gears, three stationary clutches and two rotating clutches. It is a simple, less complex design that enables the six-speed transmission to be packaged in a size not much larger than a four-speed automatic. All forward gear shifts feature clutch to clutch operation.
A new, 32-bit electro-hydraulic control module optimizes the 6L80’s performance according to a variety of vehicle inputs, while also enabling features including tow/haul mode, auto grade braking and manual range selection. The controller is integrated within the transmission.
Tow/haul mode is a driver-selectable feature that reduces shift busyness when towing or hauling a heavy load. The feature is complemented by manual range selection or “tap-up/tap-down” capability which allows the driver to manually select upshifts and downshifts with a button on the column shifter. Auto grade braking is available when the tow/haul mode is selected and the transmission is not in the range selection mode.
*Preliminary, pending certification. A new voluntary power and torque certification procedure developed by the SAE Engine Test Code committee was approved March 31, 2005 . This procedure (J2723) ensures fair, accurate ratings for horsepower and torque by allowing manufacturers to certify their engines through third-party witness testing. GM was the first auto manufacturer to begin using the procedure and expects to use it for all newly rated engines in the future.
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