Consumer Reports criticizes small turbo engines for misleading performance, economy
02-05-13, 08:57 AM
#1
Consumer Reports criticizes small turbo engines for misleading performance, economy
Consumer Reports criticizes small turbo engines for misleading performance, fuel economy claims
Consumer Reports has taken aim at at small-displacement, forced-induction engines, saying the powerplants don't manage to deliver on automaker fuel economy claims. Manufacturers have long held that smaller, turbocharged engines pack all power of their larger displacement cousins with significantly better fuel economy, but the research organization says that despite scoring high EPA economy numbers, the engines are no better than conventional drivetrains in both categories. Jake Fisher, director of automotive testing for Consumer Reports, says the forced induction options "are often slower and less fuel efficient than larger four and six-cylinder engines."
Specifically, CR calls out the new Ford Fusion equipped with the automaker's Ecoboost 1.6-liter four-cylinder engine. The institute's researchers found the engine, which is a $795 option over the base 2.5-liter four-cylinder, fails to match competitors in acceleration and served up 25 miles per gallon in testing, putting the sedan dead last among other midsize options.
The Chevrolet Cruze, Hyundai Sonata Turbo and Ford Escape 2.0T all got dinged for the same troubles, though Consumer Reports has found the turbo 2.0-liter four-cylinder in the BMW 328i does deliver on its promises
CONSUMER REPORTS TESTS FIND MANY SMALL TURBO ENGINES FALL SHORT ON FUEL ECONOMY PROMISES
Fuel Economy, Acceleration No Better than in Conventional Powertrains
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 that 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.
The full report can be found online at ConsumerReports.org.
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.
The latest example of underperforming small turbocharged engines is the collection of 2013 Ford Fusions with EcoBoost engines - small, turbocharged four-cylinders with direct injection -which were recently tested by Consumer Reports. The smaller engine - a 1.6-liter producing 173 hp - is a $795 option over the basic conventional 2.5-liter Four on Fusion SE models. But that car's 0-60 mph acceleration time trails competitive family sedans, and it delivers just 25 mpg, placing it among the worst of the crop of recently-redesigned family sedans.
The most direct comparison among the vehicles Consumer Reports has tested is the Chevrolet Cruze. CR tested both a Cruze with the base 1.8-liter conventional four-cylinder, and one with the smaller 1.4-liter turbocharged Four. While the 1.4-liter feels marginally more powerful in daily driving, it was barely faster to 60 mph, and got the same fuel economy as the larger engine.
The Hyundai Sonata Turbo, Kia Sportage Turbo, and Ford Escape 2.0T are examples of cars with turbocharged 4 cylinder engines that are less fuel efficient than V6 models in the same class, Consumer Reports found.
Consumer Reports has also found some turbocharged four-cylinder models that do deliver good fuel economy and acceleration: BMW's new 2.0-liter turbocharged four gets 28 mpg in the new 328i Sedan and delivered improved mileage in the 2012 X3 SUV by one mpg, with essentially identical power and acceleration. Volkswagens using that company's 2.0-liter turbo also return impressive mileage, though CR hasn't tested any model variations with other engines that are directly comparable.
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.
Fuel Economy, Acceleration No Better than in Conventional Powertrains
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 that 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.
The full report can be found online at ConsumerReports.org.
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.
The latest example of underperforming small turbocharged engines is the collection of 2013 Ford Fusions with EcoBoost engines - small, turbocharged four-cylinders with direct injection -which were recently tested by Consumer Reports. The smaller engine - a 1.6-liter producing 173 hp - is a $795 option over the basic conventional 2.5-liter Four on Fusion SE models. But that car's 0-60 mph acceleration time trails competitive family sedans, and it delivers just 25 mpg, placing it among the worst of the crop of recently-redesigned family sedans.
The most direct comparison among the vehicles Consumer Reports has tested is the Chevrolet Cruze. CR tested both a Cruze with the base 1.8-liter conventional four-cylinder, and one with the smaller 1.4-liter turbocharged Four. While the 1.4-liter feels marginally more powerful in daily driving, it was barely faster to 60 mph, and got the same fuel economy as the larger engine.
The Hyundai Sonata Turbo, Kia Sportage Turbo, and Ford Escape 2.0T are examples of cars with turbocharged 4 cylinder engines that are less fuel efficient than V6 models in the same class, Consumer Reports found.
Consumer Reports has also found some turbocharged four-cylinder models that do deliver good fuel economy and acceleration: BMW's new 2.0-liter turbocharged four gets 28 mpg in the new 328i Sedan and delivered improved mileage in the 2012 X3 SUV by one mpg, with essentially identical power and acceleration. Volkswagens using that company's 2.0-liter turbo also return impressive mileage, though CR hasn't tested any model variations with other engines that are directly comparable.
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.
02-05-13, 09:14 AM
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There is only a given amount of energy you can produce using gasoline. Effectively, power costs fuel. This has always been the case. The only time a turbo engine is more efficient than a larger displacement engine is when it's not "on the boost". Consumers hate turbo lag so modern turbocharged engines are designed to provide immediate boost under lower loads. Additionally, due to a lower compression ratio, forced-induction engines not "on the boost" are weaker than an equivalent naturally-aspirated engine at a given RPM.
Automobile manufacturers are gaming the system; as they always have. This is why many modern cars will attempt to shift to its top gear as soon as it can despite the negative characteristics that go along with that behavior. It scores a higher EPA MPG rating and draws people in to the showrooms. It's only after the buyers part with their cash that they realize it's a chore to operate the vehicle they've purchased.
Automobile manufacturers are gaming the system; as they always have. This is why many modern cars will attempt to shift to its top gear as soon as it can despite the negative characteristics that go along with that behavior. It scores a higher EPA MPG rating and draws people in to the showrooms. It's only after the buyers part with their cash that they realize it's a chore to operate the vehicle they've purchased.
02-05-13, 09:39 AM
#4
Cr
Small turbocharged engines are marketed as delivering the power of a large engine, with the fuel economy of a smaller 1. 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 4-cylinder engines. The smallest 1—a 1.6-liter producing 173 hp—is a $795 option over the basic conventional 2.5-liter 4 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 4-cylinder engines, get an additional 2, 5, and 6 mpg, respectively. And all accelerate more quickly.
The larger among Ford's EcoBoost 4-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 4-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.
Chevrolet-Cruze-Eco-badge.jpgAnother example is our tests of the Chevrolet Cruze. Our base Cruze had the 1.8-liter 4-cylinder; our higher-end 1LT version came with the 1.4-liter turbo 4 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.
1 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 1 of the tested cars have slower mid-range acceleration from 45-65 mph.
In contrast, BMW's turbocharged 4-cylinder engines seem to deliver both good fuel economy and acceleration: The 2.0-liter turbocharged 4 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 6-cylinder 2011 X3 we tested, with essentially identical power and acceleration but somewhat comprised refinement. The 2.0-liter turbo 4 cylinder engine we've tested in Audis and Volkswagens usually return impressive mileage, though we haven't tested any identical model powered by 2 different engines for such a direct comparison.
PHP Code:
Model Engine 0-60 mph EPA mpg CR mpg
Ford Fusion 1.6L Turbo 4 8.9 28 25
Hyundai Sonata 2.4L Four 8.2 26 27
Kia Optima 2.4L Four 8.6 27 25
Toyota Camry 2.4L Four 8.4 28 27
Honda Accord 2.4L Four 7.7 30 30
Nissan Altima 2.4L Four 8.2 27 31
Ford Fusion 2.0L Turbo 4 7.4 26 22
Hyundai Sonata 2.0L Turbo 4 6.6 26 25
Kia Optima 2.0L Turbo 4 6.6 26 24
Toyota Camry 3.5L V6 6.4 25 26
Honda Accord 3.5L V6 6.3 25 26
Nissan Altima 3.5L V6 6.3 23 24
Chevrolet Cruze 1.4L Turbo 4 9.8 28 26
Chevrolet Cruze 1.8L Four 10.5 27 26
Dodge Dart 1.4L Turbo 4 8.6 31 29
Dodge Dart 2.0L Four 11.0 27 27
Ford Escape 1.6L Turbo 4 9.9 25 22
Honda CR-V 2.4L Four 9.2 25 23
Kia Sportage 2.4L Four 10.3 23 22
Toyota RAV4 2.5L Four (2012) 10.0 24 23
Ford Escape 2.0L Turbo 4 8.2 24 22
Kia Sportage 2.0L Turbo 4 7.1 22 21
Toyota RAV4 3.5L V6 (2012) 6.7 22 22
BMW X3 2.0L Turbo 4 7.3 24 23
BMW X3 3.0L Six 7.2 21 22
Ford F-150 3.5 V6 Turbo 7.7 17 15
Ford F-150 5.0L V8 7.8 16 15
02-05-13, 10:34 AM
#5
Pole Position
There is only a given amount of energy you can produce using gasoline. Effectively, power costs fuel. This has always been the case. The only time a turbo engine is more efficient than a larger displacement engine is when it's not "on the boost". Consumers hate turbo lag so modern turbocharged engines are designed to provide immediate boost under lower loads. Additionally, due to a lower compression ratio, forced-induction engines not "on the boost" are weaker than an equivalent naturally-aspirated engine at a given RPM.
02-05-13, 10:49 AM
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Looks like the 328i is the only one to do the turbo right. 
Hopefully the NX200t is going to be done just as right as well.
BTW the 4-cylinder Camry displaces 2.5 liters, not 2.4, unless CR did the test 2 generations ago.
Hopefully the NX200t is going to be done just as right as well.BTW the 4-cylinder Camry displaces 2.5 liters, not 2.4, unless CR did the test 2 generations ago.
02-05-13, 10:56 AM
#7
you are going to see more and more of this as more companies move to turbos for CAFE standards. Its even harder to obtain EPA mileage on turbos vs NA cars, you'd have to drive them even more carefully. If turbos were so amazing they would be more prevalent before the CAFE standards started kicking in. They weren't for a reason, and this surge in turbocharged engines is only due to manufacturers responding to CAFE standards.
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02-05-13, 11:33 AM
#8
Lexus Champion
There is only a given amount of energy you can produce using gasoline. Effectively, power costs fuel. This has always been the case. The only time a turbo engine is more efficient than a larger displacement engine is when it's not "on the boost". Consumers hate turbo lag so modern turbocharged engines are designed to provide immediate boost under lower loads. Additionally, due to a lower compression ratio, forced-induction engines not "on the boost" are weaker than an equivalent naturally-aspirated engine at a given RPM.
Automobile manufacturers are gaming the system; as they always have. This is why many modern cars will attempt to shift to its top gear as soon as it can despite the negative characteristics that go along with that behavior. It scores a higher EPA MPG rating and draws people in to the showrooms. It's only after the buyers part with their cash that they realize it's a chore to operate the vehicle they've purchased.
Automobile manufacturers are gaming the system; as they always have. This is why many modern cars will attempt to shift to its top gear as soon as it can despite the negative characteristics that go along with that behavior. It scores a higher EPA MPG rating and draws people in to the showrooms. It's only after the buyers part with their cash that they realize it's a chore to operate the vehicle they've purchased.
Do you have any idea how FI work at all? Turbo's take the unused wasted kinetic energy to improve on the same displacement size engine, yet give more power than you would otherwise have in a NA setup. Additionally, newer tech such as twin-scroll, DI, valve timing, etc. have enable lower spool, higher compression, better ignition timing without the old school setbacks of previous generations. It's all in the tuning that an engineer does to the car. We used to actively joke on the Evo forums to have a switch to enable the ECU to go from a 500hp setup to a 50mpg setup in an instant. It was definitely doable, but most people were to lazy and/or want power first so it wasn't worth the investment in dyno tuning time.
Yes, turbochargers use the otherwise wasted energy from the hot exhaust to spin a turbine, which in turn turns a compressor to force more air (greater than ambient air pressure) into the engine's cylinders. But once you have more air in the cylinders, you need more fuel also. Higher-pressure air by itself (without added fuel to burn) is not going to provide the power you need and will not provide the power to spin the turbocharger to keep providing the higher-pressure air into the cylinders. You cannot have something for nothing.
Theoretically, a turbocharged engine can be more efficient than a larger-displacement engine of the same power (but less efficient than the same-displacement engine of lesser power), as long as you can keep the engine out of boost for long enough periods. Once the turbocharged engine is being boosted, it will be burning more fuel.
So, if your engine is too small (as in a 1.6-litre engine driving a Ford Fusion), it will be under boost for greater periods of time to provide the power required. And the greater periods of time the engine is under boost, the more fuel it burns.
Does that BMW 328i have the 8-speed transmission? If so, it is likely the close ratios (and very tall high gear/deep overdrive) of the transmission that help to keep the engine out of boost, and maximize fuel efficiency of the turbocharged engine.
02-05-13, 11:43 AM
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The 328i single-handedly proves that, when done right, a turbo 4 can deliver both performance and fuel economy in one package.
Last edited by ydooby; 02-05-13 at 12:06 PM.
02-05-13, 01:22 PM
#10
Lexus Champion
Agreed they seem to have got it right with this engine. C&D recently did a comparo which included the 328i and Audi A4 2.0t. In this test they both did 0-60 in 5.6 seconds and on the 300 mile test loop the BMW averaged 21 mpg and the Audi 20 mpg.
02-05-13, 01:31 PM
#11
Pole Position
Outrage is correct. If you pump more air into the cylinders, you will require more fuel to burn also.
Yes, turbochargers use the otherwise wasted energy from the hot exhaust to spin a turbine, which in turn turns a compressor to force more air (greater than ambient air pressure) into the engine's cylinders. But once you have more air in the cylinders, you need more fuel also. Higher-pressure air by itself (without added fuel to burn) is not going to provide the power you need and will not provide the power to spin the turbocharger to keep providing the higher-pressure air into the cylinders. You cannot have something for nothing.
Theoretically, a turbocharged engine can be more efficient than a larger-displacement engine of the same power (but less efficient than the same-displacement engine of lesser power), as long as you can keep the engine out of boost for long enough periods. Once the turbocharged engine is being boosted, it will be burning more fuel.
Yes, turbochargers use the otherwise wasted energy from the hot exhaust to spin a turbine, which in turn turns a compressor to force more air (greater than ambient air pressure) into the engine's cylinders. But once you have more air in the cylinders, you need more fuel also. Higher-pressure air by itself (without added fuel to burn) is not going to provide the power you need and will not provide the power to spin the turbocharger to keep providing the higher-pressure air into the cylinders. You cannot have something for nothing.
Theoretically, a turbocharged engine can be more efficient than a larger-displacement engine of the same power (but less efficient than the same-displacement engine of lesser power), as long as you can keep the engine out of boost for long enough periods. Once the turbocharged engine is being boosted, it will be burning more fuel.
02-05-13, 06:49 PM
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There is only a given amount of energy you can produce using gasoline. Effectively, power costs fuel. This has always been the case. The only time a turbo engine is more efficient than a larger displacement engine is when it's not "on the boost".
A 200hp 2.0L turbocharged 4-cylinder engine making 200hp is more efficient than a 200hp 3.0L NA 6-cylinder engine because you have far lower overall friction in the smaller engine and more BMEP (brake mean effective pressure) in the smaller engine as well which directly contributes to improved combustion efficiency.
Old turbocharged engines fell apart because they ran port injection and lower 8-9:1 compression ratios vs. 10:1 or higher for NA. They're far less efficient and waste a lot more fuel when OFF boost and not on it, such as when cruising down the highway because of the low compression ratio and resulting low BMEP. Fuel burned under lower pressure creates less power and burns less efficiently. Old turbocharged engines also had another problem in that because the turbochargers of the time didn't tend to spool or really get going below 3000rpm, the turbo engines also had to run shorter overall gearing to keep them on the edge of the boost availability zone to avoid constant downshifting and being really annoying, especially if an automatic. A 2.0L turbocharged 4-cylinder running 2700 rpm on the highway is loses much of its lower friction profile advantage when compared with a 3.0L NA 6-cylinder turning only 2000rpm, oh and is also running 10:1 compression or higher as well.
Direct injection and modern turbochargers have resolved all of these issues. With direct injection you can run typically a full point higher compression than you could before, so 10:1 compression ratios are now possible in turbo engines that are also making significant amounts of power. The quick spooling turbos that can make full boost available at extremely low RPMs also mean they can now turn those extra tall gears. No need to run closer to 3000rpm at highway speeds anymore. 2000 or way lower is fine.
Yes, the BMW and VW engines prove that turbocharged engines done right are indeed more powerful and more efficient than NA engines.
Here's where I think they're going wrong, or there's the potential to go wrong.
DESIGN - De-tuning for regular fuel. The Ford EcoBoost 2.0L engine runs a 9.3:1 CR and is designed to be compliant with regular grade fuel. That's part of the problem, but people in the U.S. are allergic to premium fuel so that's what they did. I had an Escape with this rental for a week and under acceleration I felt what I'm pretty darned sure was ignition timing getting yanked even with a 9.3:1 CR. I bet it would have run better if premium was in it, and mileage might have even gone up also. This engine has very similar specs to the BMW N20, but lower compression and design for regular fuel and even apparently some issues on regular, whereas the BMW was designed for premium. That's probably a good part of the difference.
DESIGN - same size class takes the friction argument out of the equation: If you're comparing a 1.6L 4-cylinder turbo to a 2.0L 4-cylinder NA engine, there's really not going to be a whole lot of difference in overall friction profile between the two, so that part of the smaller and more efficient engine equation goes out the window. The biggest difference you see is when you can still get the power you need yet drastically reduce engine size and overall friction profile. I don't think that difference is there if you're comparing a 1.6 to a 2.0 and both are 4-cylinder, but it IS there when you're comparing a 2.0L 4-cylinder to a 3.0L 6-cylinder.
DRIVER - EASIER TO BURN MORE FUEL WITH A TURBO!!!!
: Thanks to making tons and tons of torque from very low RPMs, it's very easy and tempting as a driver to want to tap into that _ALL THE TIME_. When you end up burning more fuel as a result, don't blame the engine for being less efficient when your DRIVING is the cause. If you're tapping into the power then you're burning more fuel period, and probably not driving nearly as efficient as you could be.
Consumers hate turbo lag so modern turbocharged engines are designed to provide immediate boost under lower loads. Additionally, due to a lower compression ratio, forced-induction engines not "on the boost" are weaker than an equivalent naturally-aspirated engine at a given RPM.
Automobile manufacturers are gaming the system; as they always have. This is why many modern cars will attempt to shift to its top gear as soon as it can despite the negative characteristics that go along with that behavior. It scores a higher EPA MPG rating and draws people in to the showrooms. It's only after the buyers part with their cash that they realize it's a chore to operate the vehicle they've purchased.
Last point, if you look at discrepancies in that chart you can see that plenty of the NA engines didn't make their rated EPA mileage vs CR's testing either, but in the article at their site only the turbo engines that didn't match are bolded and not the NA ones. That's a bit misleading.
Last edited by SteVTEC; 02-05-13 at 06:53 PM.
02-05-13, 07:20 PM
#15
