First Drive: 2012 Buick LaCrosse eAssist
By Jason Cammisa
It seems that two of the unlikeliest brands, Lincoln and Buick, are among the most progressive thinkers in the entry-level American luxury car market: both now offer no-cost hybrid versions of their cars. The Lincoln MKZ is a full hybrid, but Buick has gone a slightly less aggressive route -- though no less intelligent -- with its LaCrosse eAssist.
For the 2012 model year, buyers of the full-size LaCrosse can choose between two powertrains at the same base price: a newly fortified, 303-hp 3.6-liter V-6, or a 2.4-liter four-cylinder with a mild hybrid system strapped on.
“Mild hybrids,” as we call them, can’t propel the vehicle under electric power alone. They perform the same main function as other hybrids, which is that they recapture kinetic energy that would have otherwise been lost to heat in the braking system, store it in a battery, and then use it to propel the car at a later time. The LaCrosse’s hybrid system, along with some other intelligent tweaks to aerodynamics and rolling resistance, posts an enormous gain in EPA ratings: last year’s four-cylinder scored 19/30 mpg; the eAssist version bumps those numbers to 25/36. That’s subcompact fuel economy in a full-size car. (We averaged an indicated 29 mpg over a 120-mile mostly back-road route with three passengers and air conditioning.) Best of all, the hybrid system’s additional torque helps this new LaCrosse get to 60 mph 0.2 seconds sooner than the last car, according to Buick.
The performance increase is possible because the LaCrosse’s simple hybrid system doesn’t add a lot of weight. Total curb weight is within 6 lb of the non-hybrid car -- to offset the extra weight of the 0.5-kWh battery, wiring, and motor/generator, the eAssist LaCrosse uses aluminum in a few key areas -- wheel hubs and hood, to name two -- that were previously steel.
The battery is mounted behind the rear seats, and trunk space suffers a bit: its capacity drops from an already smallish 13.3 cubic feet to 10.9. But the LaCrosse has an enormous back seat -- a worthwhile tradeoff if you carry more passengers than cargo.
To assist in the miserly mission, the 6-speed automatic has been revised for reduced friction. Called the Gen II Hydra-Matic 6T40, the new transmission performs shifts more quickly and will appear in other GM products in the future. The final drive ratio has been significantly lengthened, from 3.23:1 to 2.64:1, and as a result, first gear is loooong: at the 7000-rpm fuel cut, the LaCrosse is doing 43 mph. It also means the engine is asleep in top gear on the highway. Thankfully, shift quality is excellent, since two-gear downshifts are occasionally necessary to maintain cruising speed on hilly interstates.
Like everything else in the LaCrosse, the direct-injection four-cylinder is impressively smooth, quiet, and refined. The transmission is programmed to rev the snot out of it in normal driving, giving the impression that this Buick isn’t arguing with your right foot -- and the end result is that a four-cylinder winds up being quite sufficient in a 3800-lb car.
Perhaps the most impressive thing about the LaCrosse is the refinement of its stop-start system. Without the tachometer needle dropping, you would never know that the car has switched itself off. There is no shudder, there is no nudge -- it is completely imperceptible. Likewise, there’s almost no sign that the engine is starting back up when you pull your foot off the brake pedal -- other than that the tach jumps up and the Buick starts to quietly creep forward.
Getting credit for this (in addition to the engineers’ masterful programming) is the belt-driven motor/generator under the hood. This device replaces the alternator, and is used for stop/start, to assist the engine under acceleration, and for brake-energy regeneration. It can contribute 15 hp and 79 lb-ft of torque to the engine’s output and generate a maximum of 15kW (20 hp) of electricity under deceleration. Using a belt, instead of gears, isolates the motor/generator from the driveline, so it’s completely silent in operation.
The Buick LaCrosse eAssist doesn’t use a typical hybrid blended brake master cylinder, so its brakes feel no different than any other nonhybrid vehicle. This is a very good thing. Like last year’s four-cylinder model, it uses electric power steering, which isn’t nearly as natural feeling as the hydraulic steering in the V-6 model, but does completely eliminate torque steer.
The best part about the LaCrosse, though, is that from behind the wheel, there’s no real price to pay for the enormous (31.5% city, 20% highway) fuel economy benefits. The eAssist drives just as well as the regular LaCrosse did. Smooth, quiet, and comfortable -- and that’s exactly what Buick customers want. Just with far better fuel economy.
The LaCrosse now starts at $30,820, a jump of nearly $3000 compared to last year’s base four-cylinder model, but Buick has made significant additions to the standard equipment list, including dual-zone climate control and alloy wheels.
We’re big fans of the one-price, choose either V-6 power or compact-car fuel economy strategy. Especially in this case, where the V-6 receives 23 hp more and the four-cylinder is not only faster, but significantly more fuel efficient. We’ll be watching the model mix carefully -- whether buyers opt for the four or six-cylinder will speak very clearly about entry-level full-size luxury buyers’ priorities.
Credit: Automobile Magazine (www.automobilemag.com)
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