Study questions efficacy of key fuel-efficiency technologies

on Sep10

Emissions Analytics gathered data using a portable system strapped to the back of its test vehicles.

They are the technologies at the heart of a decades-long effort to save fuel and cut emissions around the world: turbocharging, stop-start systems, lightweighting and eco-drive settings.

Yet when these methods move out of the lab and into the real world, not all of them actually help.

That’s according to Emissions Analytics, an independent U.K.-based company that has tested more than 500 vehicles in the U.S. since 2013. Using portable testing gear on real cars in real driving situations, EA has been working to determine what trends in the automotive space actually have a meaningful impact on fuel economy and greenhouse-gas emissions.

EA plans to release its full findings on U.S. vehicles in early October. The goal, according to Nick Molden, the company’s founder and CEO, is to give consumers an accurate and unbiased look at the true fuel economy and CO2 emissions of the vehicles they’re interested in and their true impact on the environment.

“You can only decide if you have the right information,” Molden told Automotive News. “The EPA sticker is — I would say — good up to a point, but we can give a lot more information.”

EA gathered its data using a portable emissions measurement system strapped to the back of a vehicle. Over an 88-mile course on public roads in Southern California, the portable device measures carbon dioxide, nitrogen oxides and other emissions, along with fuel economy. (The company has tested more than 1,000 vehicles globally.)

Keeping it real

Emissions Analytics has tested more than 500 vehicles on public roads in the U.S. to determine which technologies are most effective in reducing emissions and fuel consumption. Here’s how it does that testing:

    • Instrument: Portable emissions measurement device strapped to the back of each test vehicle

    • Measurements: Carbon monoxide, carbon dioxide, total hydrocarbons, nitrogen oxides, fuel economy and fuel consumption.

    • Test course: 88 miles on public roads in Southern California that takes about 140 minutes to drive. Includes 6 passes on the nearby freeway (2 with AC on max, 2 with it off) averaging 65 mph, plus a 22-turn surface-street route with elevation changes and a 22.5 mph average that’s run twice with the AC on max and twice with it off.

    • Vehicles: Usually sourced from media partners (such as Motor Trend), rental agencies and EA’s network of contacts. Each vehicle has 1,000 to 5,000 odometer miles and is tested in the default drive setting.

    • Fuel: Standardized Chevron gasoline in regular, premium and diesel varieties


The results of the tests cast a cloud over an era of purported progress in fuel economy. Four years of results in the U.S. show no actual improvement in overall fuel economy and no decrease in CO2 emissions, according to EA.

Vehicles with engines smaller than 2 liters have seen essentially no change in fuel economy; vehicles with engines 2 to 3 liters (the most common) have seen fuel economy decrease by around 8 percent, while vehicles with engines 3 liters or larger have seen an 8 percent increase in fuel economy.

This decrease among the most common vehicles is magnified in the U.S. because Americans are commuting longer distances without switching to smaller vehicles.

“If like-for-like the vehicles are not becoming cleaner, those other two shifts are actually going to drag up total CO2 emissions,” Molden said.

There’s a sliver of good news: The EPA’s five-cycle test procedure is currently pretty accurate when compared with Emissions Analytics’ real-world tests.

But Molden pointed out that with stricter fuel economy regulations looming in the U.S., automakers could be lured into relying too heavily on efforts that have little real-world impact.

Consumers who pay attention to a brand’s fuel-economy credentials should be wary of automakers relying too heavily on “off cycle” credits, Molden said.

Off-cycle credits are those given to automakers by the EPA for technologies that help cut fuel use but aren’t accounted for in the standard city and highway test cycle. These include features such as engine stop-start during idle, “eco” driving modes, active grille shutters that improve aerodynamics and even ventilated seats, which can reduce the need for air conditioning.

Some brands use these technologies to make actual — though nominal — mpg gains, while others use them for “window dressing,” Molden said.

Their usefulness can even vary from model to model within a specific manufacturer, though he declined to name the most egregious offenders.

But it’s turbocharged engines that are particularly susceptible to large gaps between lab and street results. When a turbocharged engine is being tested under low stress and thus not engaging the turbos themselves, it produces significant fuel savings over a naturally aspirated engine. But once the turbos are engaged, the engine becomes far less efficient than a nonturbo unit.

“Downsizing is a good thing up to a point,” Molden said.

“You go past a certain inflection point and actually you can find that the real-world mpg will actually get worse if you go too small.”

Downsizing is most effective when moving from larger engines — above 2 liters — to 2 liters.

“As soon as you start going below 2 liters, that’s where we start seeing the gaps open up between EPA sticker and real world,” Molden said.

So what kind of technologies are successful in cutting fuel use and reducing CO2 emissions?

Start with hybrids — the plain-Jane type that have been overlooked recently as plug-in hybrid EVs and pure EVs have come into vogue, Molden says. Regular hybrids still offer significant cuts to CO2 and NOx and have highly sophisticated tuning to make sure they run at optimal efficiency rates and wring out excellent mpg results.

Plus, they’re cheaper to build and operate than PHEVs and EVs and offer the best use case for the widest range of consumers. And they’re no longer incentivized by most governments, so their sales amid low gasoline prices reflect a baseline of sustainable market demand.

Beyond the garden-variety Prius, EA’s EQUA Index shows that technologies such as multispeed transmissions, lightweighting of the vehicle overall and proper tire choice (that is, not large-diameter rims wrapped in ultra-thin rubber) have a meaningful real-world impact that drivers will notice.

“There’s so much good technology out there,” Molden said. “There are genuine efficiency improvements happening. The marketplace just needs to know so people can then choose the right vehicles when they’re in the showroom.”



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