Buick's 2012 LaCrosse comes standard with a hybrid electric power train, but the company just calls it "electric assist" for its luxury car buyers (a decision apparently made by the marketing types).
Earlier this week, this editor and fellow members of the New England Motor Press Association were given a detailed preview of the new LaCrosse—which significantly is the first car model (other than a dedicated hybrid line) to be sold with its "base" version (called eAssistTM
) having a hybrid powertrain. The V6 version sells for the same price ($30,620, delivered).
What impressed me was how GM engineers took last year's 4-cylinder engine and integrated a hybrid drive and battery, along with a new 6-speed automatic transmission, to produce an economical and smooth functioning package. A motor/generator replaces the conventional alternator and also functions as both a regenerative brake to charge the battery pack and a start/stop motor to allow shutting down the internal combustion engine when stopped in traffic. The motor/generator links to the engine/transmission via a 7-groove mechanical belt design to be under tension in either direction (thus dual tensioners) during application of electrical power or regenerative braking.
The motor/generator is liquid cooled and produces 15 hp, with 110 ft-lb (150 Nm) of torque to crank the engine in start/stop operation and 79 ft-lb (107 Nm) for assist at launch, on grades, and for highway acceleration. For initial start on a day's drive, there is a conventional 12V battery and starter motor.
The 115V, 0.5 kWh Li-ion battery pack consists of 32 cells the size of Red Bull cans and weighs 65 lb (29 kg)—about half the size of other hybrid car packs. The pack and control electronics sit over the rear axle, and, even with its fan and cooling air ducting, is small enough to allow clearance for a usable pass-through to the passenger cabin, about 16 inches wide.
Warranty period for the eAssist system is eight years or 100,000 miles, with the motor/generator belt specified for a 75,000 mile service interval.
According to Al Houtman, GM vehicle performance manager for front wheel drive hybrid programs, the hybrid system electrical management algorithms are based on those developed for the Chevy Volt
. Operation is optimized to use the motor/generator augmentation for "torque smoothing" and to allow the internal combustion engine (2.41L, 182 hp, and 172 ft-lb torque) to run near its most efficient point as well as maintain battery state of charge.
Engine control architecture also implements a deceleration fuel cutoff regimen to further improve fuel economy. The result is U.S. EPA mileage ratings of 25 mpg (city) and 36 mpg (highway) using regular gas, improvements over last year's 4-cylinder model of 32 and 20%, respectively. (The V6 LaCrosse comes in at 17 mpg (city) and 27 mpg (highway) with its 303 hp.)