The Active Fuel Management system GM uses on its 4.3-liter V-6 and 5.3- and 6.2-liter V-8 engines could not be more different from EcoBoost.
Over the years, GM has taken some lumps from critics for sticking to its overhead valve "small block" engine architecture that dates to the 1950s. The layout places the cam in the center of the engine, where it operates the valves with pushrods and rocker arms. It is low-cost and low-tech compared with overhead-cam engines. But cylinder deactivation works with less complexity and expense on pushrod engines than on overhead-cam engines.
GM's system shuts down two cylinders under light load conditions, such as when cruising at a steady speed. It turns a V-6 into a V-4 and a V-8 into a V-6.
Air trapped in the deactivated cylinders acts as springs and reduces engine drag. GM has spent years tweaking the technology. It is now so seamless that most drivers can't feel the engine as it switches cylinders off and on, although engine noise is slightly higher when the system is operating. GM says Active Fuel Management yields about 7.5 percent better fuel economy.
The knock on Active Fuel Management is that the rpm range that it works in is narrow and even the slightest pressure on the accelerator will switch off the system. GM owners reporting their fuel economy on forums and on the EPA's fueleconomy.gov Web site show real-world performance very close to the window label number. Some drivers claim to get higher than the EPA window label number. But when towing, Active Fuel Management-equipped engines suffer the same fate as EcoBoost: Hook up a heavy load and the fuel economy plummets.
Still, EcoBoost and Active Fuel Management can deliver impressive fuel economy gains -- if used judiciously.
Consider the new 4.3-liter V-6 base engine in the Chevrolet Silverado, GM's highest volume nameplate. It carries a 24 mpg highway fuel economy rating, up from the 20 mpg in the old V-6 truck and -- more important -- 2 mpg higher than Ford's F-150 with its 3.5-liter EcoBoost engine.
"When Ford brought out its modular V-8 engine family in the 1990s, the focus wasn't on fuel economy," said AutoPacific analyst Dave Sullivan. Performance and technology were more important, he said.
Some estimates place the cost of installing Active Fuel Management -- oil-pressure operated solenoids that turn off valve lifters, and computer controls -- at between $50 and $100 per vehicle. Meanwhile, Ford's turbochargers, intercoolers, heat abatement and other equipment that make up EcoBoost likely costs at least five times more depending on the application, experts say.
Ford charges a minimum of $1,000 to add an EcoBoost engine to a vehicle.
GM charges nothing extra for Active Fuel Management, which comes standard on the 4.3-, 5.3- and 6.2-liter engines.
Active Fuel Management helps give the 6.2-liter, 455-hp Chevy Corvette an impressive 29 mpg EPA highway rating.
"Now, pushrods make sense again," Sullivan said.