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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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By EricMartello on 2/7/2013 9:51:50 AM , Rating: 1
Turbos allow smaller engines that are more efficient because they have less internal friction, and the reduced weight improves overall vehicle efficiency.

No, they do not have less internal friction. They do have lower static compression, but for a given power output both a turbo and NA engine will consume similar amounts of fuel which is what we're talking about. Efficiency is a measure of fuel consumed per unit of power produced.

Turbo engines are not substantially lighter than their NA counterparts because turbo engines (the reliable ones) have iron blocks. An NA engine can be perfectly reliable with a substantially lighter aluminum block.

Turbos also produce more lower end torque so the average engine rpm is lowered, also increasing efficiency.

That depends how the engine is tuned and what type of turbo you are using. A small turbo will produce more low-end torque at the expense of mid-range and top-end power - this translates to anemic performance on the highway when trying to pass or merge.

There is a myth being perpetuated on many car forums that engines that produce large amounts of low end torque are "better" because "most driving occurs at this RPM". This is not true. Your engine will regularly spin up past 3-4K RPM during normal driving unless you're driving like granny, and your low-end torque will nose-dive right around 4K RPM which means the acceleration from ~30 MPH to ~75 MPH (typical highway speeds) is going to be pitiful.

The IDEAL is an engine that has a broad, flat torque curve that does not fall off and allows the engine to rev higher and produce more usable power.

However, the trend is toward regenerative braking which reduces some losses associated with higher curb weight, and better materials, drivetrains, and lubricants have reduced the impact of friction.

Regenerative braking is not relevant in this discussion. That has to do with using braking forces to charge a battery of a hybrid or electric vehicle rather than dissipating all of that energy as heat. It adds cost and complexity to the vehicle, with an unclear advantage in terms of improving efficiency.

High rpm operation loses significant amounts of power to frictional losses and fluid turbulence.

That's simply false.

Turbos also produce more lower end torque so the average engine rpm is lowered, also increasing efficiency.

Also false. You don't seem to get it. Torque is the ability of an engine to move a given weight a certain distance. Power determines how quickly the torque can be applied. It has nothing to do with a turbo - it's how the engine is configured.

There is no "efficiency" gain from a low-end torque bias in a vehicle that is not REGULARLY towing, plowing or otherwise moving large loads at slow speeds. This is marketing mythology that is highly prevalent on VW and Audi forums as justifications for how "great" the 2.Slow T engine is that seems to be in all of their cars.

However, the trend is toward regenerative braking

There is no trend toward regenerative braking and you clearly don't understand what it is or how it why bother bringing it up?

Go inflate your tires with helium so that your "effective weight" is reduced and your car drives like "it's floating on a cloud". $200 per tire filled.

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