Press Release
New 6.2L V8 and 6-Speed Automatic Lead Powertrain Offerings
The fourth-generation of GM's legendary small-block V-8 engine is the power behind the 2007 GMC Yukon and Yukon Denali -led by the Yukon Denali's exclusive 6.2L V-8 rated at 380-horsepower (283 kw).* This all-new, all-aluminum engine uses variable valve technology to optimize performance, fuel efficiency and emissions. Performance and efficiency is enhanced by a new six-speed automatic transmission with tap up/tap down shifting.
In all Yukon models, the range of available small-block V-8s delivers more power and better fuel economy than the models they replace. In fact, with fuel saving technology, such as Displacement On Demand, and other vehicle refinements, the vehicles deliver the best fuel economy in the full-size SUV segment.
A 5.3L small-block V-8 is standard on all Yukon models -except the 2WD base Yukon -and is rated at 320 horsepower (238 kw)* and 340 lb.-ft. of torque (470 Nm),* an 8 percent horsepower increase compared to the previous 5.3L engine. A Flex-Fuel E85 version, which is capable of running on E85 ethanol fuel or a mixture of E85 and gasoline, is standard on 4WD models and available on 2WD models. E85 is comprised of 85 percent ethanol, which is a renewable resource fuel produced in the United States . A 4.8L V-8 engine, rated at 290 horsepower (216 kw)* is the standard engine of Yukon 2WD base models and will be available later in the '06 model year.
All new Vortec engines represent the fourth generation of the small-block V-8, which debuted in 1955. Highlights include:
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Revised cylinder block design
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Displacement On Demand on 5.3L engine
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Electronic throttle control
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58X ignition system
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New, more powerful E38 32-bit controller
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Enhanced quietness and smoothness
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Returnless fuel system
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 provide up to seven percent increased fuel efficiency when measured against a comparable non-DOD 5.3L engine. DOD 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.
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. 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.
Yukon and Yukon Denali's new Gen IV small-block engines also meet more stringent emissions standards. 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 (the largest source of vehicle emissions).
Yukon Denali 's 6.2L engine
The 6.2L engine of the Yukon Denali is all-new, with advanced technologies and lightweight materials -including variable valve timing and an aluminum cylinder block -contributing to the vehicle's uncompromising performance. Along with its 380 horsepower (283 kw),* the engine produces 415 lb.-ft. of torque (564 Nm).*
The aluminum-block Gen-IV engine of the Yukon Denali is similar to the high-performance 6.0L LS2 V-8 found in the Pontiac GTO and Chevy Corvette, but is engineered for truck capabilities. The use of an aluminum cylinder blocks offers reduced mass, an attribute that supports improved vehicle weight distribution and slightly improved fuel economy. The block is virtually identical to the iron version, including a deep skirt design that incorporates cross-bolted main bearing caps and a structural oil pan. It also features crankcase "windows” -vents that help improve bay-to-bay breathing -which reduces pumping losses and supports the high horsepower output of the high-performance engine.
Variable valve timing (VVT) 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 overhead valve engine. The unique dual-equal phaser adjusts the camshaft timing at the same rate for both the intake and exhaust valves.
The VVT 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 retard ignition timing at higher rpm levels to increase power. At lower rpm levels, torque is enhanced with advanced timing.
This cam phaser feature was pioneered by GM and introduced in 2005 on the new 3.5L and 3.9L V-6 engines -a first for the use of variable valve timing on a overhead valve engine design. 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 more quickly and accurately than previous systems that used just a single segment. Also, a leaf spring-type tensioner is used on the timing chain to reduce noise and eliminate slack.
Much of the 6.2L engine's significant power increase, compared with previous Yukon Denali engines -approximately 14 percent more horsepower -comes 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.
Quiet, durable operation
All Gen IV small-block Vortec V-8 engines are designed for quieter operation, which contributes to the new vehicles' more civilized and quieter driving experience. Engine quieting features include:
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Special friction-reducing coating on piston skirts
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Full floating piston pins
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Damping patch on the oil pan
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Timing chain tensioner
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Quieter alternator
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Acoustically tuned engine cover
Stronger engine cradles and mounting systems help reduce vibrations transmitted through the chassis that would otherwise be felt by 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.
New 6L80 six-speed automatic
GM's new, Hydra-Matic 6L80 electronically controlled six-speed automatic transmission is matched with the Yukon Denali's 6.2L engine. Yukon 's 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 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.
Further 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.
Backing the engine and transmission team is an enhanced rear axle system that supports the increased power and capabilities of the Gen IV powertrains. They are mounted to the chassis with stiffer brackets and special bushings that help reduce noise and vibration.
A limited-slip axle is available, as is a locking differential. Axle ratios range from 3.42:1 to 4.10:1. A new, low rolling-resistance/low-friction pinion bearing design is used to help reduce driveline friction and enhance fuel efficiency. The rear axle carrier has thicker, stronger tubes and the rear cover pan is 50-percent thicker than previous designs.
*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.
