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Report: Small turbo engines don't deliver on economy claims 
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Consumer Reports finds small turbo engines don't deliver on fuel economy claims
Feb 5, 2013 12:01 AM

Small turbocharged engines are marketed as delivering the power of a large engine, with the fuel economy of a smaller one. That's a tempting proposition, but our testing shows these small-displacement turbos are not delivering on the promises.

By now, we've tested many cars with these engines, and lots of competitors with traditional, naturally-aspirated powerplants, big and small. Generally, the turbocharged cars have slower acceleration and no better fuel economy than the models with bigger, conventional engines. Looking at 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.

The latest example is the collection of EcoBoost Ford Fusions we tested, which come with small, direct-injection, turbocharged four-cylinder engines. The smallest one—a 1.6-liter producing 173 hp—is a $795 option over the basic conventional 2.5-liter four cylinder on Fusion SE models. But that 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.

The larger among Ford's EcoBoost four-cylinder engines, the turbocharged 231-hp, 2.0-liter, is billed as having the power of a V6 but delivering the fuel economy of a four-cylinder. However, our so-equipped Fusion Titanium returned 22 mpg (which pales against the 25 and 26 mpg we recorded for the best V6 family sedans), slower acceleration and reduced refinement compared to its V6-powered peers.

Another example is our tests of the 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 cylinder. 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.

Turbochargers 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.

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 turbocharged models deliver that benefit. 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.

In contrast, BMW's turbocharged four-cylinder engines seem to deliver both good fuel economy and acceleration: The 2.0-liter turbocharged four cylinder contributes to 28 mpg overall in our last tested 328i sedan. It improved mileage only marginally in the 2013 X3 SUV compared to the six-cylinder 2011 X3 we tested, with essentially identical power and acceleration but somewhat comprised refinement. The 2.0-liter turbo four cylinder engine we've tested in Audis and Volkswagens usually return impressive mileage, though we haven't tested any identical model powered by two different engines for such a direct comparison.


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http://news.consumerreports.org/cars/2013/02/consumer-reports-finds-small-turbo-engines-dont-deliver-on-fuel-economy-claims.html

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Thu Feb 07, 2013 6:09 pm
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I'm not sure I agree with that, be interested to know how they tested. The benefit of a turbo is that you're only using more fuel when on boost.

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Thu Feb 07, 2013 7:25 pm
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tombolt wrote:
I'm not sure I agree with that, be interested to know how they tested. The benefit of a turbo is that you're only using more fuel when on boost.


I'm guessing the point about small turbo engines is that the turbo is generally used more often as the aspirated part of the range doesn't have sufficient shove to match the performance of the normally aspirated engines these units are intended to replace. For example, Fords 1L Ecoboost units are normally used to replace 1.6L aspirated engines.

WhatCar has been consistently finding the economy of Fords Ecoboost units to be severely lacking in the real world compared to their official consumption figures.
For example, the Focus 1.0 Ecoboost 125 has an official combined economy of 56.5 mpg but the magazines TrueMPG figure is between 35.0 and 38.2 mpg depending on the trim level (from the March 2013 issue). There's also a tool on their website to check the cars they've tested that also explains the methodology they've used - True MPG.

In fairness, the vast majority of cars 'official' figures are miles off real world performance but some are much worse than others.

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Thu Feb 07, 2013 7:38 pm
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Oh yes, nobody should buy a car based on official figures, they're just a basis for comparison.

Maybe I'm being unfair, but I suspect a bias from a source with an agenda. It all depends on how the tests are conducted. I would suggest, that they're not testing them under usual conditions, but conditions that favour the larger engine.

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Thu Feb 07, 2013 7:51 pm
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tombolt wrote:
I'm not sure I agree with that, be interested to know how they tested. The benefit of a turbo is that you're only using more fuel when on boost.


If you click through to the original article, there's some hotlinks in the text.
http://www.consumerreports.org/cro/2012/12/how-consumer-reports-tests-cars/index.htm -

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Consumer Reports operates the largest and most sophisticated independent automobile testing center devoted to the consumer interest anywhere in the world. Situated on 327 acres in rural Connecticut, the Consumer Reports Auto Test Center is home to more than 20 staff members, including automotive engineers, technicians, and support staff. Consumer Reports buys, anonymously, all the cars it tests, about 80 per year, and drives each for thousands of miles.

Formal testing is done at the track and on surrounding public roads. The evaluation regimen consists of more than 50 individual tests. Some are objective, instrumented track tests using state-of-the-art electronic gear that yield empirical findings. Some are subjective evaluations-jury tests done by the experienced engineering staff. These videos will provide further insights into the ways that Consumer Reports evaluates new cars to help its readers make smart, informed choices. (Watch our car-review videos.) See our Guide to Consumer Reports Ratings.

~~~ deletia ~~~

Fuel economy

We perform our own fuel-economy tests, independent of the government's often-quoted EPA figures and the manufacturers' claims. Using a precise fuel-flow measuring device spliced into the fuel line, we run three separate circuits. One is on a public highway at a steady 65 mph. That circuit is run in both directions to counteract any wind effect. A second is a stop-and-go simulated city-driving test done at our track. The third is a 150-mile "one-day trip" using several drivers taking turns around a 30-mile loop of public roads that include a highway section, secondary roads, and rural byways. CR's overall fuel-economy numbers are derived from those three fuel consumption tests.

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Thu Feb 07, 2013 8:00 pm
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Hmm, okay. It doesn't match what I see in my own life though, which is that small, turbo engines are generally more economical.

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Thu Feb 07, 2013 8:51 pm
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Their assertion is that where firms are swapping a larger engine for a turbo'd small capacity engine, in the same body, there's no benefit.
I imagine that in your experience, the small turbo'd engines are in small, light cars.
Taking the diesel out of your land, for instance, and swapping in a smaller turbo block wouldn't necessarily magically give you better mpg.

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Thu Feb 07, 2013 9:28 pm
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Yes, I'd sort of missed that. The engine without turbo would have to be capable of pulling the car, or you'd be on boost all the time. I'd sort of thought that was a given, but maybe the manufacturers aren't doing that in all cases.

One of my examples is the guilietta qv. a 1.7 (1.8 actually) turbo with 230hp in a similar weight car to my 3.2 with 250hp. I get around 25mpg, they get around 32. The crucial thing there is that there was a 1.8 version of my car and it was more than capable of pulling the car, it actually went pretty well.

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Thu Feb 07, 2013 9:38 pm
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The figures are generally atrocious. I haven't had a car in the last 20 years which couldn't manage over 40mpg...

Well, the BMW M535i would drop below 30 if hammered, but I still managed 40mpg on a 100mph tour across Germany. 8-)

My Laguna 2L petrol automatic made 42mpg, the Passat 2L petrol 50mpg, Mondeo 2L turbo diesel 50mpg, even my current Verso 2.2L turbo diesel automatic manages around 40mpg.

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Fri Feb 08, 2013 5:48 am
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big_D wrote:
The figures are generally atrocious. I haven't had a car in the last 20 years which couldn't manage over 40mpg...

Well, the BMW M535i would drop below 30 if hammered, but I still managed 40mpg on a 100mph tour across Germany. 8-)

My Laguna 2L petrol automatic made 42mpg, the Passat 2L petrol 50mpg, Mondeo 2L turbo diesel 50mpg, even my current Verso 2.2L turbo diesel automatic manages around 40mpg.

Yes but that consumer report is from the US, and they have lower efficiency standards and ultra efficient cars are not allowed to be exported to the US because of the impact on the fuel duty.

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Fri Feb 08, 2013 9:58 am
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Amnesia10 wrote:
big_D wrote:
The figures are generally atrocious. I haven't had a car in the last 20 years which couldn't manage over 40mpg...

Well, the BMW M535i would drop below 30 if hammered, but I still managed 40mpg on a 100mph tour across Germany. 8-)

My Laguna 2L petrol automatic made 42mpg, the Passat 2L petrol 50mpg, Mondeo 2L turbo diesel 50mpg, even my current Verso 2.2L turbo diesel automatic manages around 40mpg.

Yes but that consumer report is from the US, and they have lower efficiency standards and ultra efficient cars are not allowed to be exported to the US because of the impact on the fuel duty.

The USA has a smaller gallon, so obviously lower miles per gallon. 40mpg in UK is 33mpg in US gallons.

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JJW009 wrote:
Amnesia10 wrote:
Yes but that consumer report is from the US, and they have lower efficiency standards and ultra efficient cars are not allowed to be exported to the US because of the impact on the fuel duty.

The USA has a smaller gallon, so obviously lower miles per gallon. 40mpg in UK is 33mpg in US gallons.

There was something that I read somewhere that was about a version of the VW Passat that was not allowed to be sold in the US. The end result was that too many efficient cars would lower the revenue of the minuscule fuel tax that they have there, which is used to fund road repairs in the US.

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JJW009 wrote:
The USA has a smaller gallon, so obviously lower miles per gallon. 40mpg in UK is 33mpg in US gallons.


Doh! Of course.

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tombolt wrote:
JJW009 wrote:
The USA has a smaller gallon, so obviously lower miles per gallon. 40mpg in UK is 33mpg in US gallons.


Doh! Of course.

But they are still not making cars anywhere near as efficient as Europe or Asia.

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tombolt wrote:
JJW009 wrote:
The USA has a smaller gallon, so obviously lower miles per gallon. 40mpg in UK is 33mpg in US gallons.


Doh! Of course.

I remember hearing about a plane that crashed because they confused gallons for litres. They reset the fuel gage to "full" after filling, and it ran out mid-air.

It would be so much safer if the whole world used standard measures all the time.

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