Small turbos may not deliver

Fuel economy, acceleration no better than in conventional powertrains

February 6, 2013
by Fleet Management staff

YONKERS, NY—Although small turbocharged engines are marketed as delivering the power of a large engine with the fuel economy of a smaller one, Consumer Reports tests have found they often fall short of expectations. Many turbocharged cars tested by CR have slower acceleration and no better fuel economy than the models with bigger conventional engines.

“While these engines may look better on paper with impressive EPA numbers, in reality they are often slower and less fuel efficient than larger four and six-cylinder engines,” said Jake Fisher, director of automotive testing for Consumer Reports.

Consumer Reports tests many cars with small, turbocharged engines, and lots of competitors with traditional, naturally aspirated engines, big and small. Based on the EPA fuel-economy estimates, which are calculated based on laboratory tests, some of these cars’ turbocharged engines look better. But CR’s engineers found those results don’t always translate to the real world driving and in Consumer Reports’ own fuel economy tests.

Consumer Reports notes that turbochargers pump extra air into the engine to deliver more power. But gasoline 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.

The full report, including a chart comparing different models’ acceleration and fuel economy, can be found here.