/2012 Buick LaCrosse eAssist

2012 Buick LaCrosse eAssist

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All 2012 models of Buick LaCrosse will be fitted as standard with the clever eAssist fuel saving technology which using “smart electrification” will result in fuel consumption figures of 37 mpg highway and 25 mpg city, with no compromises in the driving experience. It does not make the LaCrosse a hybrid, because the car can’t run purely on electricity, but it does help the engine when you need power.

With a state-of-the-art lithium-ion battery system and electric motor-generator to enable regenerative braking capability, not only the fuel efficiency is improved by 25 percent, but also the system’s 15-kW motor-generator that is fed by the batteries power will join the 2.4L Ecotec direct injection four-cylinder engine mated to next-generation six-speed automatic transmission, to give good acceleration.

The engineers have also worked on the car’s underbody aerodynamics and tires for maximum efficiency. It comes with active control of front-end airflow that improves aerodynamics and engine warm-up. Electronically controlled shutters in the lower grille close at higher speeds to push more air over the vehicle, which increases aerodynamic efficiency to enhance fuel economy.

LaCrosse with eAssist includes an ECO gauge on the instrument panel that continuously responds to driving behavior, enabling the driver to drive with maximum efficiency. It also features a hill-assist system that captures brake pressure to help the driver more comfortably accelerate from a stop on a moderate or steep grade.

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eAssist details

While the eAssist system shares the same basic belt-alternator-starter configuration of previous BAS designs, it delivers more than three times the power and is much more capable than the previous-generation BAS system.

“The eAssist system is more than just the next-generation BAS system. The ability to integrate regenerative braking with the latest lithium-ion battery technology creates a system that delivers significant fuel-efficiency gains that customers will enjoy,” said Steve Poulos, global chief engineer of the eAssist system. “Being able to provide electric boost to the powertrain system during heavy acceleration and grade driving enables the LaCrosse transmission to operate more efficiently, while the added functionality of engine start-stop and fuel shut-off during deceleration provides added fuel savings.”

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. That compares with only 2 kW of power assist and 5 kW of regenerative power on the previous BAS system. The greater power capability enables greater energy capture during regenerative braking for improved fuel economy.

The system also enables the Ecotec engine to shut down fuel delivery in certain deceleration conditions, which saves additional fuel. While in fuel shut-off mode, the motor-generator unit continues spinning along with the engine to provide immediate and smooth take-off power when the driver presses on the accelerator. Then, as the vehicle comes to a stop, the motor-generator unit spins the engine, bringing it to a smooth stop – properly positioned for a smooth restart.

“The battery system is designed to provide power assistance to the internal combustion engine, rather than storing energy for all-electric propulsion,” said Poulos. “It’s really an extension of the conventional internal combustion engine, not a replacement for it.”

The eAssist power pack contains the lithium-ion battery pack, the integrated power inverter and 12V power supply. It is located in a compartment between the rear seat and trunk; and it is surprisingly compact and lightweight, weighing only about 65 pounds (29 kg). It still allows rear access to the trunk via the split-folding rear seat – an attribute not shared with other hybrid competitors. Trunk space is slightly reduced when compared with 2011 models with the four-cylinder/six-speed powertrain, but still offers 10.9 cubic feet (307 liters) of storage. An electric fan cools the power pack, drawing air from a vent located in the package tray, behind the rear seat. The fans are designed to be quiet from the cabin.

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 motor-generator is a high-performance, compact induction motor that is liquid-cooled for increased performance and efficiency.

Next-generation six-speed

The eAssist system works with LaCrosse’s direct injected 2.4L Ecotec four-cylinder and next-generation six-speed automatic powertrain combination. In the LaCrosse with eAssist, the engine is rated at approximately 180 horsepower (134 kW) and the next-generation Hydra-Matic 6T40 takes transmission technology to the next level with features designed to enhance powertrain efficiency.

Significant internal transmission changes to clutch controls and hardware provide reduced spin losses while improving shift response and time. The added electric power provided by the eAssist system allows for higher gearing to improve steady state efficiency without impacting acceleration performance or driveability. The system’s capability of providing some electric assistance at cruising speeds allows the driver to accelerate lightly or ascend mild grades without the transmission downshifting.

An auxiliary, electric-driven transmission oil pump is added to the 6T40, which keeps the transmission primed and the fluid flowing when the engine shuts down at a stop. That keeps the transmission ready to perform when the driver accelerates, for a seamless, uncompromised driving experience.
“It’s a very integrated powertrain system, with no compromises in driving performance, shift quality or ride and handling,” said Daryl Wilson, LaCrosse lead development engineer. “We believe this combination points to the future of vehicles powered primarily by an internal combustion engine.”

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Model: 2012 LaCrosse with eAssist technology
Body style / driveline: front-drive, front-engine, four-door, five- passenger sedan
Construction: integral
EPA vehicle class: midsize sedan
Manufacturing location: Kansas City, Kan.
Key competitors: Acura TL, Lincoln MKZ, Lexus ES350


Type: Ecotec 2.4L DOHC I-4
Displacement (cu in / cc): 145 / 2384
Bore & stroke (in / mm): 3.46 x 3.85 / 88 x 98
Block material: precision sand cast aluminum
Cylinder head material: SPM cast aluminum
Valvetrain: overhead camshafts, four-valves per cylinder, continuous variable valve timing for intake and exhaust
Ignition system: individual coil-on-plug
Fuel delivery: direct injection and electronic throttle control
Compression ratio: 11.2:1
Horsepower (hp / kW @ rpm): 182 / 136 @ 6700 rpm*
Torque (lb.-ft. / Nm @ rpm): 172 / 233 @ 4900 rpm*
Recommended fuel: regular unleaded
Emissions controls: close-coupled, catalytic converter; variable valve timing; positive crankcase ventilation evaporative system
Estimated fuel economy (city / hwy): 25 / 37


Type: Hydra-Matic 6T40 six-speed automatic
Gear ratios: (:1):
First: 4.58
Second: 2.96
Third: 1.91
Fourth: 1.45
Fifth: 1.00
Sixth: 0.75
Reverse: 2.84
Final drive ratio: 2.64:1

Electric Drive System

Type: belt-driven, liquid-cooled motor/generator unit and lithium-ion battery system; air-cooled power electronics and battery pack
Maximum electric generating power 15 kW @ 1570-3180 rpm
Maximum electric motor torque (cranking) 110 lb.-ft. / 150 Nm
Maximum electric motor torque (electric assist) 79 lb.-ft. / 107 Nm @ 1,000 rpm
Maximum electric motor power (electric assist) 15 hp / 11.2 kW @ 1,000-2,200 rpm
Lithium-ion battery 115V, 0.5-kWh, 15 kW peak power


Suspension (front): MacPherson strut coil-over-spring; twin-tube dampers with gas-charged valving; hollow direct-acting stabilizer bar
Suspension (rear): four-link
Steering type: electric variable-ratio, rack-and-pinion
Steering ratio: 15.2:1
Steering wheel turns, lock-to-lock: 2.75
Turning circle (ft / m): 38.8 / 11.75


Type: split, dual-circuit four-wheel-disc with power assist
Rotor diameter x thickness (in / mm): front: 12.6 x 1.2 / 321 x 30 (vented)rear: 12.4 x 0.9 / 315 x 23 (solid)
Total swept area (cu in / mm): TBD


Wheel size and type: 17-inch steel with cover
Tires: P245/50R17 all-season blackwall


Wheelbase (in / mm): 111.7 / 2837
Overall length (in / mm): 197 / 5003
Overall width (in / mm): 73.1 / 1858
Overall height (in / mm): 59.2 / 1503
Track (in / mm): front: 61.7 / 1567rear: 62 / 1576
Curb weight (lb / kg): 3835 / 1739


Seating capacity: 5 (2 front / 3 rear)
Headroom (in / mm): front: 38 / 965rear: 37.3 / 948
Legroom (in / mm): front: 41.7 / 1058rear: 40.5 / 1029
Shoulder room (in / mm): front: 57.4 / 1459rear: 56 / 1423
Hip room (in / mm): front: 55.2 / 1402rear: 53.9 / 1368


EPA interior volume (cu ft / L): 99 / 2805
Passenger volume (cu ft / L): 101.7 / 2878
Cargo volume (cu ft / L): 10.9 / 307
Trailer towing maximum (lb / kg): TBD
Fuel capacity (gal / L): 15.7 / 59.4
Engine oil (qt / L): 5 / 4.7
Cooling system ( qt / L): TBD
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(Founder / Chief Editor / Journalist) – Arman is the original founder of Motorward.com, which he kept until August 2009. Currently Arman is our chief editor and is held responsible for a large part of the news we publish.