Active fuel management system fosters fuel efficiencies

GMC Yukon took top honors in the full-size SUV category of AutoPacific’s 15th annual Vehicle Satisfaction Awards, the Southern Calif.-based automotive marketing and consulting firm announced recently.

The awards are based on the firm’s survey of more than 68,000 vehicle owners.

Earlier this year, Yukon topped the full-size SUV category of IntelliChoice’s 2011 Best Overall Values of the Year awards, based on analysis of ownership costs, including depreciation, maintenance, repairs, fuel, fees, financing and insurance.

Automotive critics also laud the Yukon.Truck Trendrecently named GMC Yukon the “Best in Class 2011 Full-Size SUV,” citing fuel-efficient hybrid model, active fuel management, up-to-nine-passenger seating and 8,200-pound towing capacity as strengths.

Active Fuel Management

Active Fuel Management enables many of the V8 engines in GMC Sierra pickups and Yukon SUVS to behave like a four-cylinder engine when cruising with light loads while seamlessly unleashing full muscle whenever needed. Engineers pioneered the concept of variable displacement engines, but the idea really came into its own with the development of modern electronic engine management systems and sequential fuel injection.

Under light load conditions when only a fraction of the available power keeps the vehicle moving, the fuel delivery to four of the eight cylinders switches off and a solenoid system collapses the valve lifters to reduce the pumping losses and improve fuel efficiency. As soon as the vehicle begins climbing a grade or the driver needs to accelerate to complete a pass, those cylinders are automatically and transparently re-enabled.

On the GMC Sierra and Yukon Hybrid models, engineers used the ability of the sophisticated two-mode system to provide electric drive-assist at highway speeds so the 6.0-liter Vortec V8 can be kept in four-cylinder mode longer. Where a standard pickup or SUV might switch back to eight-cylinder mode while ascending a grade, the hybrids use their electric motors to maintain speed and keep four cylinders turned off, helping these trucks achieve best-in-class EPA estimates of 20 miles-per-gallon in the city and 23 mpg on the highway.

The AFM-equipped 2011 GMC Sierra XFE has EPA estimates of 15 mpg city and 22 mpg highway. AFM also is used on the standard 5.3-liter Sierra and Yukons with the 5.3-, 6.0- or 6.2-liter V8 as well as several Chevrolet pickups and Chevrolet and Cadillac SUVs.