The 2008 GMC Yukon Hybrid, featuring the world's first two-mode hybrid propulsion system in an SUV, will offer consumers a 25-percent improvement in overall fuel economy when it arrives at dealerships toward the end of next year.
The GMC Yukon Hybrid is powered by an aluminum small-block Vortec V-8 engine that maintains important performance attributes of full-size trucks, such as towing at 6,000 pounds. To offset the added weight from the hybrid propulsion system, GM redesigned certain vehicle components to optimize aerodynamics. These design changes include a new hood, front and rear fascias and a sleek GMC grille.
The first mode of the system is for low speed and light loads. In this mode, the hybrid system can operate with electric power only, engine power only and any combination of engine and electric power. When the first mode operates as electric only, fuel consumption is reduced in heavy stop-and-go traffic by shutting off the engine for extended periods of time and moving exclusively under electric power at low speeds.
The second mode is primarily used at highway speeds. In addition to electric assist, the second mode integrates sophisticated electronic controls, such as Active Fuel Management, cam phasing and late-intake valve closure, to allow even more efficient engine operation with electric motors less than half the size of a traditional "one-mode" hybrid system. Full eight-cylinder engine power is provided when conditions demand it, such as passing, towing or climbing a steep grade.
The two-mode system also leverages a four-speed automatic transmission and electronic controls in an integrated, powerful and compact system that can be used with gas and diesel engines, front- and rear-wheel-drive configurations and cars, trucks and SUVs.
"The GMC Yukon Hybrid will be equipped with unique powertrain technology that provides a terrific combination of fuel economy, performance and towing capability in a full-size SUV," said Tom Stephens, group vice president, GM Powertrain. "The Yukon Hybrid's 25-percent composite fuel efficiency improvement highlights GM's commitment to save as much fuel as possible by applying hybrid technology to the highest fuel-consuming vehicles first."