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Not all small turbo engines are more fuel-efficient says Consumer Reports

Consumer Reports isn't letting up on its testing of fuel efficiency claims for various vehicles. According to the publication, small turbocharged engines aren't delivering on the fuel efficiency claims by the manufacturers.

Small displacement turbocharged engines have become common in a variety of vehicles in place of larger displacement, naturally aspirated engines. The claim by the automotive manufacturers is that the small displacement turbocharged engines offer the same power as larger displacement engines and improved fuel efficiency.

Consumer Reports, however, states that in its real world testing many vehicles with turbocharged engines aren't as efficient as the manufacturers claim. The publication recently tested the 1.6-liter EcoBoost in a Ford Fusion and found that the turbocharged version has a slower 0-to-60 mph time than its competitors and achieved only 25 mpg in testing, making it among the worst for fuel efficiency in the recent crop of family sedans.

The publication also claims that the larger 2.0-liter turbocharged four-cylinder, which promises the power of the V-6 with the fuel economy of four-cylinder engine, fails to deliver on either front.

2013 Ford Fusion

Chevrolet is also under fire for the 1.4-liter turbo four-cylinder in the Cruze. Consumer Reports claims that real world performance wasn’t much better than the standard, naturally aspirated 1.8-liter engine and overall fuel economy was similar as well.
Ford and General Motors representatives offered similar statements explaining the discrepancy. "When you have an EcoBoost engine, you have the opportunity to have performance and fuel economy, but not at the same time,” said Ford Powertrain Communications Manager Richard Truett. “EcoBoost adds a dimension that you won't get by just making the engine smaller. We're telling the driver, it's up to you on how you want to drive."

"The Cruze turbocharged engine provides a much broader torque curve than a non-turbocharged engine, and that means better acceleration across the rpm range, making for a more fun-to-drive car,” said GM spokesman Tom Read. “However, if you have a heavy foot on a turbocharged engine, you're not necessarily going to see a lot of fuel economy benefits."

The EPA is going to investigate Ford after Consumer Reports and other owners have complained that fuel efficiency doesn't meet the automakers claims in the Fusion Hybrid and C-MAX.

Source: Consumer Reports

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RE: Weight
By JediJeb on 2/5/2013 8:53:17 PM , Rating: 2
Vehicle weight and the torque output and torque curve are more important than pure HP numbers. If an engine gets more torque at a low rpm near what you are cruising at than another then that engine can be geared to produce better mileage.

I had an old 2.3L I4 Mustang that got worse mileage than most 5.0L V8 models. The little engine just did not have the power and had to be geared much lower just to move the car. Another way to think about it is displacement versus operating rpm. A 1.6L engine operating at 5000rpm displaces the same volume of air/fuel as a 2.67L engine operating at 3000 rpm. Given that stoichiometrically you get the same amount of energy from the same amount of fuel/air(minus the minor efficiency differences) then you should get the same mileage from a 1.6L engine running 5000rpm to achieve 70mph as you would from a 2.67L engine running at 3000 rpm to achieve 70mpg. Both of those engines are consuming 4000L of fuel/air mixture per minute running at the respective 5000 and 3000 rpm and 4000L will have the same BTUs produced in each engine.

Now where you can make one engine better than the other is in the design of the leverage in the piston/crankshaft geometry to gain more torque at lower rpm so that your gearing can be higher(lower ratio)at the final drive axle. If you can't manage to get the torque needed at a low enough rpm on the little turbo I4 it will not beat the mileage of a larger engine that can.

This is why I like the 4.9L I6 in my truck over the 5.0L V8 because the I6 has much more torque at lower rpm. While I can not rev the engine up over 5K rpm and smoke the tires, I can be in 5th gear by the time I am at 30mph without bogging the engine down. Long stroke inlines for low end torque, short stroke engines for higher rpm horsepower. Both have their uses and their detriments.

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