New V-8s Deliver Greater Power and Efficiency in 2015 GMC Yukons – including 6.2L with Segment-Best 420 HP

2014-02-24

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NAPA, Calif. – Advanced technologies in the 2015 GMC Yukon lineup’s new EcoTec3 V-8 engines deliver more power with greater efficiency – including segment-best city and highway fuel efficiency with the Yukon’s standard engine and the segment’s highest power and torque ratings for the Yukon Denali models. 

Yukon and Yukon XL feature a standard 5.3L engine, rated at 355 horsepower (265 kW) and 383 lb.-ft. of torque (519 Nm), which enables EPA-estimated 16 mpg in the city and 23 mpg on the highway for 2WD models – efficiency increases of nearly 10 percent on the highway and 7 percent in city driving, compared to previous models.

Yukon Denali and Yukon XL Denali models feature an exclusive 6.2L V-8 rated at 420 horsepower (313 kW) and 460 lb.-ft. of torque (623 Nm). No other full-size SUV offers as much power and torque. Denali models are also rated at 15 city / 21 highway (2WD models).

“GMC Yukon’s powertrains represent the rare instance where more power is delivered with less fuel consumption, giving customers the confidence of power on demand for any situation and the benefit of greater efficiency,” said Sheryl Balsley, assistant chief engineer for Small Block engines. “The capability of the engines to instantly switch to four-cylinder mode, for example, improves efficiency when less power is required, but delivers full eight-cylinder power whenever it’s needed.”

Both of the new EcoTec3 engines feature state-of-the-art technologies, including direct injection, Active Fuel Management (cylinder deactivation), continuously variable valve timing and an advanced combustion system, designed to make the most of power, torque and efficiency across a broad range of operating conditions.

Improved engine mounts, electronic throttle control, adaptive exhaust systems, improved aerodynamics and other technologies help the engines operate in four-cylinder mode longer with Active Fuel Management, further increasing efficiency.

A Hydra-Matic 6L80 six-speed automatic transmission is paired with both engines and contributes to efficiency with reduced engine speed on the highway. It also features TapShift control, Tow/Haul mode and Auto Grade Braking.

Advanced combustion system

At the heart of the new EcoTec3 engine family is an advanced combustion system that maximizes the potential of the direct fuel injection system, cylinder deactivation, continuously variable valve timing and other technologies to ensure a strong balance between on-demand performance and real-world efficiency.

The ability to more precisely control combustion also enables the new engines to run with a higher compression ratio, one of the best ways to simultaneously increase power and efficiency.

This increased efficiency can now be maintained over a broader range of operating conditions. For example, when towing a trailer on a steep grade on a hot day, the advanced combustion system can reduce the need to trim back spark advance to control detonation, helping maintain efficiency with confident performance.

Direct injection and Active Fuel Management

The engines’ direct fuel injection system precisely meters fuel directly into the cylinders, helping optimize combustion over a broad range of conditions. An all-new cylinder head design supports the fuel system and it’s complemented by a new, sculpted piston head developed to direct the injector’s fuel spray for better mixing and more complete combustion. 

To further enhance combustion, the intake and exhaust valve positions have been switched from the previous Small Block engine design, and the spark plug angle has been revised to move the electrode closer to the center of the chamber to support optimal combustion.

In certain light-load driving conditions, half of the injectors quit spraying fuel, effectively turning the engine into a V-4 to help increase efficiency. This cylinder deactivation technology, also known as Active Fuel Management, is standard. It uses oil pressure, controlled by the powertrain control module, to deactivate the lifters on selected cylinders, closes the valves for those cylinders, and seamlessly reactivates the cylinders when the driver demands greater power. The transition takes less than 20 milliseconds and is virtually imperceptible.

“This is another great example of using a relatively simple mechanical system and powerful software to provide a real benefit to our customers,” said Balsley.

Additional features on the EcoTec3 engine family include:

Weight-saving aluminum engine block: A lightweight aluminum block with iron cylinder liners provides a light, rigid foundation for a smooth and strong engine. The deep-skirt block design helps maximize strength and minimize vibration. Cross-bolted main bearing caps are secured to the block with four main bolts and two cross bolts each. A structural aluminum oil pan further stiffens the bottom of the block. The result is an engine that is quieter, smoother and more dependable, even under the toughest conditions.

Efficiency-enhancing oiling system: The oiling system incorporates a new variable-displacement oil pump that enables more efficient oil delivery, based on the engine’s operating conditions. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm, and then delivers higher pressure at higher engine speeds to provide a more robust lubrication.

The engines use GM’s Dexos oil for increased efficiency and longer oil life. GM’s oil life monitoring system is standard and helps protect the engine by indicating oil changes based on operating conditions, which can save money by avoiding unnecessary oil changes.

Oil-jet piston cooling: At higher engine speeds, small jets spray oil on the underside of each piston to help reduce piston temperature, enabling the engine to maintain maximum horsepower and torque. It also reduces engine noise.

PCV-integrated rocker covers: New domed rocker covers house a patent-pending integrated positive crankcase ventilation system that enhances oil life, reduces oil consumption and reduces exhaust emissions. The domed sections of the covers contain baffles that separate oil and air from the crankcase gases, with about three times the oil/air separation capability of previous engines.

“Saw-cut” exhaust manifolds: The cast-iron exhaust manifolds were developed to improve durability and sealing, and reduce operating noise. They feature saw cuts along their cylinder head mounting flange, which split the flange into four separate sections, allowing each section to move under extreme hot-cold temperature fluctuations to virtually eliminate movement of the exhaust manifold gaskets. That helps ensure proper sealing for the life of the engine and reduces the chance of gasket failure. The exhaust manifolds also feature triple-layer stainless steel heat shields, which limit heat transfer to the engine bay and help further reduce noise.

Cooling system, humidity sensor and more:

  • A revised cooling system with an offset water pump and thermostat delivers more efficient performance
  • An air induction humidity sensor ensures optimal combustion efficiency, regardless of the surrounding air’s humidity
  • An engine-driven mechanical vacuum pump enhances braking performance
  • 58X ignition system with individual ignition coil modules and iridium-tip spark plugs contribute to greater efficiency and reduced maintenance requirements.

6.2L distinctions

Compared to the 5.3L engine, the 6.2L V-8 that’s exclusive to the Yukon Denali and Yukon XL Denali delivers nearly 19 percent more horsepower and about 20 percent more torque. It shares the same architecture, but features larger, 4.06-inch (103 mm) cylinder bores, compared with the 5.3L’s 3.78-inch (96 mm) bores.

The engines share a 3.62-inch (92 mm) stroke, with the 6.2L featuring a steel crankshaft. The engines also share the same advanced technologies, but the 6.2L has a “larger” camshaft that produces more valve lift and greater duration – the amount of time the valves are held open – allowing the larger-displacement engine to process the greater volume of air it can pump. The 6.2L also has a larger-diameter throttle body to draw more air.

The cylinder heads are unique on the 6.2L, too, with larger valves than the 5.3L – again, to process more air – as well as a slightly larger combustion chamber volume. The 6.2L’s valves are high-performance hollow-stem types on the intake side and lightweight sodium-filled valves on the exhaust side. The 5.3L uses conventional stainless steel intake and exhaust valves.

The 6.2L also has a higher, 11.5:1 compression ratio vs. the 5.3L’s 11:1 ratio.

GMC has manufactured trucks since 1902, with innovation and engineering excellence built into all GMC vehicles. The brand is evolving to offer more fuel-efficient trucks and crossovers, including the Terrain small SUV and Acadia crossover. GMC’s highest-volume vehicle, the Sierra pickup, is the most powerful light-duty pickup on the market, and the first full-size pickup to receive the highest-possible five-star Overall Vehicle Score for safety since the National Highway Traffic Safety Administration changed its New Car Assessment Program for the 2011 model year. Details on all GMC models are available at http://www.gmc.com/, on Twitter at @thisisgmc or at http://www.facebook.com/gmc.

2015 GMC Yukon Denali (L) and Yukon XL SLT

2015 GMC Yukon Denali (L) and Yukon XL SLT

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