First Drive: 2011 Buick LaCrosse CX gets four cylinders for fuel economy

2011 Buick LaCrosse four-cylinder – Click above for high-res image gallery

For the foreseeable future, the LaCrosse will remain the flagship of the Buick lineup, so at first glance, it might seem peculiar that General Motors is adding a seemingly modest inline-four cylinder engine to the sedan's powertrain list. However, at the time the LaCrosse was being developed in 2007-2008, gasoline prices in the United States had spiked to their highest levels ever, topping $4 per gallon. General Motors product planners were understandably working on the assumption that fuel prices would remain high and continue an upward trend in the coming years.

Although Buick officials won't say so explicitly, another factor that likely played into the decision to offer the 2.4-liter EcoTec four-cylinder engine was the underwhelming response to the new 3.0-liter direct injected V6. While the new smaller V6 is a smooth runner and produces similar power to the company's earlier 3.6-liter port injected V6, it was lacking in torque compared to its larger counterpart and actually got slightly inferior fuel economy. We recently had the chance to sample the new four-cylinder-powered LaCrosse CX in rural Virginia. Read on to find out if less is indeed more when it comes to Buick's handsome sedan.

Photos by Sam Abuelsamid / Copyright ©2010 Weblogs, Inc.

The four-pot engine going into the LaCrosse is the same direct-injected 2.4-liter EcoTec that debuted last year in the Chevrolet Equinox. Aside from the new engine, little else has changed on the LaCrosse which has only been on sale for about nine months now. Given the early acclaim that Buick has enjoyed with the LaCrosse, we weren't expecting drastic changes this early into the car's life, so the HiPer strut suspension we covered recently was quite a pleasant surprise.

As a premium brand trying to compete with the likes of Lexus and Acura, refinement remains paramount for Buick. The LaCrosse has generally been lauded for its quiet and roomy interior and high level of fit and finish. The obvious concern is that a more raucous four-cylinder could disrupt the serenity that buyers in this segment are likely to prefer. While the DI EcoTec isn't necessarily the most powerful engine in its class (the Hyundai Sonata tops it by 18 horsepower) it is a smooth runner and EcoTec chief engineer Chris Meagher discussed some of what was done to improve the refinement of the 2.4.

Previous port injected versions of the Family Two EcoTec (the larger 2.0, 2.2 and 2.4-liter variants) had used a lost foam casting process for the aluminum cylinder block. Lost foam castings are dimensionally accurate and well suited to complex parts like engine blocks. However, the resulting casting can be less dense, and when GM pioneered the process in the late-1980s for the original Saturn engines, it had issues with porosity. Those problems were eventually overcome, but newer direct injected engines have higher internal pressures and there have often been complaints about the ticking sound produced by the injectors on other DI engines.

To address this, Meagher explained that the direct injected EcoTec block is instead produced with a precision sand-casting process. The resulting part is more rigid and transmits less of the injector and combustion noise, allowing it to run quieter. On the outside of the engine, the engineers have also covered the high pressure fuel pump and injector rail with a high density foam as a noise abatement measure. Along with the variable valve timing, the 2.4 produces the same 182 horsepower and 172 pound-feet of torque as it does in the Chevy Equinox and GMC Terrain.

Buick started producing four-cylinder LaCrosses at the Fairfax Kansas assembly plant last week, and for the remainder of the 2010 model year, the I4 will only be available in the base CX model. When 2011 models are launched this summer, however, the engine's availability will be expanded to the mid-level CXL. Our CX tester was equipped with the fabric upholstery that looks like some sort of modern micro-fiber that ought to wear well over time. Leather surfaces aren't available in the CX, so if you want a four-cylinder LaCrosse with hide-covered thrones, you'll have to wait for the CXL this fall.

As with other LaCrosse models, the interior plastics are nicely grained and don't look cheap – even though many of the surfaces are hard to the touch. We could, however, do without some of the molded in fake stitching. The back seat is extremely roomy offering plenty of leg and head room. Our biggest complaint with the interior of the LaCrosse remains the outward visibility. The thick A-pillars make for very prominent blind-spots when turning or running down a curvy road. Further, the center stack, while visually pleasing, is a bit of a buttonfest and can be tough to get accustomed to.

When trolling around town or cruising down the highway the noise, vibration, and harshness (NVH) abatement measures used on the EcoTec do their part to maintain a very quiet cabin environment. At idle, the engine is barely perceptible, with no sound or vibration evident. We were unable to detect any injector ticking either at partial load or full throttle. A large resonance chamber in the intake plumbing keeps the boominess often associated with four cylinders to a minimum.

During wide open throttle acceleration, volume levels rise as expected, but the resulting noise doesn't seem any louder than the available V6 alternatives, it just lasts a bit longer since you don't get up to speed quite as quickly. While the LaCrosse has ride and handling characteristics that reflect its German engineering heritage, no one could reasonably describe the four-cylinder as a sports sedan. Thankfully, the throttle response is smooth and easily modulated – it never feels like the car is about to jump off the line, but neither does it feel like you are waiting for something to happen.

The four has enough grunt to allow the LaCrosse to safely merge into freeway traffic. However, on a two-lane road, you might want to wait for a slightly longer straight before attempting a pass than you would with a V6 model. While gearheads like those on the Autoblog staff are almost always looking for more power and more torque, the reality is that most would-be buyers will likely be completely satisfied with the performance of the four-cylinder LaCrosse. It certainly won't be an embarrassment or rolling roadblock.

Naturally, the primary reason for opting for the four-banger is fuel economy. The LaCrosse's 3.0-liter V6 scores a somewhat disappointing 17 miles-per-gallon city and 26 mpg highway (the 3.6 gets 27 mpg highway) from the EPA. The EcoTec has been officially tagged with window sticker values of 22 mpg on the urban cycle and 30 mpg on the highway cycle – substantial improvements. Our drive time was limited, but we saw 23 mpg according to the trip computer in the car on a mixed loop that included similar parts stop and go, freeway and two-lane back roads. We'll reserve final judgment until we get to spend a longer stretch with this model.

The four-cylinder LaCrosse CX starts at $26,995 including delivery, a savings of $ 840 compared to the 3.0. Buick figures that about one-quarter of LaCrosse buyers will go with the smaller engine and they should be able to start taking delivery in the next few weeks. We're guessing that once the CXL 2.4 becomes available in the Fall, it will likely be the volume leader – especially if gas prices climb precipitously again.

Photos by Sam Abuelsamid / Copyright ©2010 Weblogs, Inc.

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