2014 Chevrolet Impala, test drive in Hell, MichiganEnlarge Photo
The new 2014 Chevrolet Impala is a big five-passenger family sedan, the largest one Chevy sells.
While it was launched earlier this year with a 303-horsepower 3.6-liter V-6 engine, it can now also be ordered with a 196-hp, 2.5-liter four-cylinder Ecotec engine that produces 186 lb-ft of torque.
That would seem to be a small engine in a big car, but it’s in the service of—naturally—fuel economy. The four-cylinder Impala is rated at 25 mpg (21 mpg city, 31 mpg highway) by the EPA, better than the 22-mpg combined rating of the V-6 version.
We got a chance for a quick 20-minute drive in the new four-cylinder Impala, and found it to be fine under almost all driving circumstances on our short 12-mile route.
Big sedan, good mileage
Over that distance, it returned a recorded 25.1 mpg, which is a figure you’d not have been likely to see from previous Impalas (except perhaps during highway cruising on flat roads with the cruise control on).
It’s not nearly as good as the real-world 40 mpg we got in a 2013 Toyota Avalon Hybrid, but the Impala was slightly bigger than Toyota’s largest sedan—and several thousand dollars cheaper to boot.
But under most driving conditions, the Impala performed well enough—and, during damp and intermittently rainy weather, proved to be surprisingly eager to spin its inside front wheel when accelerating out of corners.
Canceling lugging noises
To keep engine speed, and hence fuel consumption, as low as possible, the four-cylinder Impala also uses active noise cancellation. That feature sends sound waves through the audio speakers into the passenger compartment that exactly cancel out certain engine noises that customers find disturbing.
That allows the engine to be programmed to run as low as 1,150 rpm with a locked torque converter in the six-speed automatic transmission—a behavior that used to be called “lugging”—without occupants hearing noises that might make them think something was wrong with the car.
2014 Chevrolet ImpalaEnlarge Photo
Variable intake-valve lift
GM’s new 2.5-liter four is quite a sophisticated piece of technology for a high-volume engine from the country’s largest carmaker. Not only does it have dual overhead cams and variable valve timing, but the company’s engine designers have added variable lift to the intake valves.
That means that under light power demand, the valve doesn’t open as far, letting in only as much air is needed to combust the small amount of fuel required. That reduces so-called pumping losses, essentially the power required to pump extra air in and out of the cylinder. Under full power demand, the valve opens to its full extent to let in the maximum air required to match the high volume of fuel delivered into the combustion chamber.
Less maximum power
The one circumstance under which we found the Impala to lack power was in situations where swift acceleration is suddenly needed—from, say, 30 to 60 mph. There, it almost felt as if the transmission had a gear missing, and the car should have shifted down to an even lower gear for better acceleration. The engine revved up nicely to as high as 6500 rpm, but the car simply didn’t gather speed as swiftly as we would have liked.