2012 Buick LaCrosse eAssist hybrid
Buick unveils the 2012 LaCrosse with eAssist,TM a new fuel-saving technology that increases fuel economy by 25 percent compared to the four-cylinder/six-speed powertrain in the 2011 LaCrosse. The eAssist system becomes the standard powertrain on LaCrosse starting next summer.
The system uses a state-of-the-art lithium-ion battery system and electric motor-generator to enable regenerative braking capability to improve LaCrosse fuel economy by an estimated 25 percent.
"The eAssist system is more than just the next-generation BAS system. The eAssist system's 115V air-cooled lithium-ion battery bolsters the 2.4L Ecotec four-cylinder engine with approximately 11 kW (15 horsepower) of electric power assist during heavy acceleration and 15 kW of regenerative braking power. The eAssist power pack contains the lithium-ion battery pack, the integrated power inverter and 12V power supply. The eAssist system's electric motor-generator is mounted to the engine in place of the alternator to provide both motor assist and electric-generating functions through a new engine belt-drive system. The eAssist system works with LaCrosse's direct injected 2.4L Ecotec four-cylinder and next-generation six-speed automatic powertrain combination.
It is expected to deliver 25 mpg in city driving and 37 mpg on the highway, fuel economy numbers that are up from 19-city/30 highway for the 2011 LaCrosse with the same four-cylinder engine.
Even though eAssist is similar in principle to the very mild belt-alternator-starter (BAS) hybrid system first used on the 2007 Saturn Vue Green Line and 2009 Chevrolet Malibu Hybrid, you won’t find the hybrid badge on the LaCrosse that adorned those earlier vehicles. A BAS system—sometimes called stop-start hybrid and micro hybrid—is a relatively low-tech hybrid design. Even though the LaCrosse eAssist is coming at a time when automakers are pushing toward greater degrees of electrification—and Honda for one is trying to engineer itself out of a mild hybrid approach that precludes plugging in—this lower cost type of hybrid technology deserves a place in the hybrid family. What is eAssist?
The system enhances fuel mileage by “assisting” the gasoline engine, either by shutting down the engine when the car comes to a stop or cutting off the fuel supply when cruising or decelerating. When the car comes to a stop, the motor-generator unit spins the engine, bringing it to a smooth stop and also properly positions the vehicle for a smooth restart. This new BAS design has noteworthy fuel economy gains compared to the earlier system, but neither come close to fuel mileage delivered by a “full hybrid” operation like those in the Toyota Prius and Ford Fusion Hybrid. Buick’s eAssist is closer in function and fuel economy to the “mild hybrid” systems used in the Honda Insight and BMW ActiveHybrid 7.
There’s been a lot of debate—mostly trash talk—about whether or not eAssist is a mild- or micro-hybrid, some comparing the LaCrosse and the now defunct Honda Accord Hybrid. The eAssist system doles out better fuel mileage, offering an estimated 25/37 in the LaCrosse versus 24/32 in the killed-off Accord. Guess that makes eAssist at least as a good as that mild hybrid?
More Power, Less Fuel
eAssist has a 15 kW motor-generator that replaces the original 5 kW motor. The new batteries bolster the engine with approximately 11 kW (15 horsepower) of electric power assist during heavy acceleration and 15 kW of regenerative braking power. Under the LaCrosse hood, the new eAssist teams up with a 182 horsepower 2.4-liter direct injection four-cylinder engine that generates 172 pounds-feet of torque. Additionally, the engine has an aggressive fuel shut-off during deceleration that provides added fuel savings.
Higher final-drive gearing keeps engine revs lower at highway speeds, boosting mpg. The engine and transmission are engineered to enable regenerative braking and battery charging during coasting and braking.
It’s the total package—the eAssist hybrid system and tweaks—that produce the 25/37 mpg numbers.
The LaCrosse never cuts costs with the choice of cabin materials. Fuel Economy Or V-6 Power Same Price
When the 2012 LaCrosse goes on sale this summer, Buick will offer the base model with a choice of two engines with the identical starting price of about $30,000—the eAssist four cylinder or a 3.6-liter V-6 engine. While both competitors have better in-town fuel economy than the Buick—41 mpg for the Lincoln and 35 mpg for the Lexus—the LaCrosse on the highway nudges the MKZ by 1 mpg and the HS 250h by 3 mpg.
The goal of the eAssist was to create a more fuel-efficient version of the four-cylinder LaCrosse using an evolution of the mild hybrid system used in the old Chevrolet Malibu hybrid and Saturn Aura Green Line.
