From a recent Automotive News Article.
The technology, called eAssist, is expected to boost the LaCrosse’s highway fuel economy to 37 mpg, a 7 mpg increase over the 2011 model. City driving is estimated at 25 mpg, up 6 mpg.
The system, a version of stop-start technology, will be standard on LaCrosse models equipped with a four-cylinder engine.
“This is a significant system that is going to surprise or even shock the competition,” John Schwegman, vice president of marketing for Buick-GMC, said during a press preview this month. Buick estimates a $30,000 sticker price for the 2012 LaCrosse.
eAssist integrates a small electric motor with GM’s 182-hp, 2.4-liter four-cylinder engine to boost acceleration and cut fuel use. GM calls it a belt-alternator starter system, a combined motor/generator bolted to the front of the engine.
A similar system had been offered on the Saturn Aura sedan and Vue crossover. But the system in the 2012 LaCrosse delivers more power than the previous belt-alternator system, GM said.
The LaCrosse’s electric motor charges the battery. An air-cooled 115-volt lithium battery pack takes up a small portion of the LaCrosse’s trunk. The system also incorporates a regenerative braking system, which stores electricity gained from applying the brakes for use propelling the vehicle.
The system provides 11 kilowatts (equivalent to about 15 hp) of electric power assist during heavy acceleration and 15 kilowatts of regenerative braking power, Buick said. That compares with 2 kilowatts of power assist and 5 kilowatts of regenerative power on the previous-generation belt-alternator system.
Unlike a full hybrid system, the mild hybrid LaCrosse cannot propel a vehicle on electric power alone.
To save fuel, the LaCrosse’s engine shuts off when the vehicle is stopped at a traffic light or when the vehicle is coasting to a stop. When that happens, the electricity in the battery powers such things as the climate control system, radio and headlights.
The mid-sized LaCrosse will nearly have “the fuel economy of a compact car,” Steve Poulos, chief engineer for eAssist technology, said at the Buick event.
Among the other changes to boost fuel economy: Underbody aerodynamics were improved and lower rolling-resistance tires were added. For better aerodynamics, electronically controlled shutters in the lower grille close at higher speeds.
“From a business standpoint … there is an opportunity to bring this kind of light electrification and regenerative braking to the vast majority of our vehicles,” Poulos said. “Buick has taken the first step with the LaCrosse.”