General Motors previously indicated its mild-hybrid system would reappear in future midsize sedans in late 2011, but until now, we weren't sure which model line would reintroduce the system. According to the automaker, the revised system -- now dubbed eAssist -- will be the standard powertrain on the 2012 Buick LaCrosse.
The eAssist system will be paired with all 2012 LaCrosse models fitted with GM's 2.4-liter I-4, which is mated with the company's six-speed automatic transmission. Although a similar powertrain setup -- sans the mild hybrid boost, of course -- is already offered in the 2011 LaCrosse range, eAssist promises to further improve fuel economy. According to GM, the LaCrosse with eAssist returns an estimated EPA rating of 25/37 mpg (city/highway), up from the 19/30 mpg raiting attained by the current 2.4-liter/ six-speed pairing.
As previously reported, the eAssist system is an evolution of the belt-alternator-starter -- or, as GM puts it, "light electrification" -- system previously used on the likes of the Saturn Vue Hybrid, Saturn Aura Hybrid, and Chevrolet Malibu Hybrid. GM has since upgraded the battery pack from nickel-metal-hydride to lithium-ion chemistry, while simultaneously upgrading the electric motor. The company claims the electric motor can provide a 15-horsepower boost during acceleration (bringing the system's net output to 182 horsepower), and can recover 15 kW of electricity through regenerative braking. In contrast, the last-generation BAS system could only add 3 horsepower and recover 5 kW of energy.
Unlike full hybrids, the BAS system isn't designed for full-fledged electric driving. Although the system is capable of EV propulsion at very low i.e. single-digits) speeds, GM views the system as an assistant to the gasoline engine.
"The battery system is designed to provide power assistance to the internal combustion engine, rather than storing energy for all-electric propulsion," Steve Poulos, global chief engineer of the eAssist system, said in a prepared release. "It's really an extension of the conventional internal combustion engine, not a replacement for it."
In order to maximize the potential fuel economy gains produced by eAssist, GM added a number of tweaks to the LaCrosse. MPG-conscious revisions include a revised, low-friction automatic transmission; underbody panels designed to smooth airflow underneath the car; low-rolling reistance tires; and electrically-controlled grille shutters that close at highway speeds to reduce drag.
GM expects 2012 LaCrosse models with eAssist to arrive at showrooms nationwide in the summer of 2011. Pricing has yet to be finalized, but GM estimates the base price of a CX eAssist model should be roughly $30,000 -- about $3000 over an equivalent 2011 CX without the hybrid system.