Most automakers claim that small turbo-charged engines deliver the power of a large motor, with the fuel economy of a smaller one. That's a tempting proposition, but Consumer Reports—a U.S. publication that reviews products based on comprehensive in-house testing and research— contends that these small-displacement turbos are not delivering on their promises.
Turbo-chargers pump extra air into the engine to deliver more power. But all engines have to be operated at a very specific air-to-fuel ratio. So this extra air has to be augmented with extra fuel, which may offset any savings from shrinking engine sizes.
With extensive comparison testing completed, the magazine’s experts have found that, “Generally, the turbo-charged cars have slower acceleration and no better fuel economy than the models with bigger, conventional engines. Looking at U.S. Environmental Protection Agency (EPA) fuel-economy estimates (calculated based on laboratory tests), some of these cars' turbocharged engines seem to have an advantage.”
“But we found those results don't match the findings from our own fuel-economy tests,” according to the publication.
The statement follows up on the consumer research organization’s allegations in early December 2012 that the 2013 model C-Max Hybrid and Fusion Hybrid does not live up to Ford’s fuel economy claims of 47 city/47 highway/47 combined miles per gallon (mpg).
The latest example, Consumer Reports said this week, “is the collection of EcoBoost Ford Fusions we tested,” which come with small, direct-injection, turbo-charged four-cylinder engines. The smallest one—a 1.6-liter, producing 173 horsepower (hp)—is a $795 option over the basic conventional 2.5-liter four cylinder on Fusion SE models.
“But,” said the editors, “that [Fusion SE] car's 0-60 mph acceleration time trails most competitors, and its 25 mpg overall places it among the worst of the crop of recently-redesigned family sedans. The Toyota Camry, Honda Accord and Nissan Altima, all with conventional 2.4- or 2.5-liter four-cylinder engines, get an additional 2, 5, and 6 mpg, respectively. And all accelerate more quickly.”
In addition, when Consumer Reports assessed the performance of Chevrolet Cruze, “Our base Cruze had the 1.8-liter four-cylinder; our higher-end 1LT version came with the 1.4-liter turbo four cylinders. While the 1.4-liter feels marginally more powerful in daily driving, it was barely faster to 60 mph, and it got the same fuel economy as the larger engine—26 mpg overall.”
One benefit to the turbocharged engines is an abundance of torque at low to mid rpm. In daily driving, this means a more effortless feeling of thrust with reduced need to downshift while climbing hills or when delivering the kind of moderate acceleration most drivers demand. That can make a car feel more responsive, even if its actual acceleration times from a standstill are slower.
However, not all of these turbo-charged models deliver that benefit, said the editors. “Many, especially those smaller 1.4- and 1.6-liter engines, still downshift frequently to keep up with traffic. And all but one of the tested cars have slower mid-range acceleration from 45-65 mph.”
So, the magazine warns, while automakers are getting mileage out of their claims, drivers may not go the advertised distance.
Edited by Braden Becker