Pictures: A Rare Look Inside Carmakers’ Drive for 55 MPG

Smoking Out Savings

Photograph by Jeffrey Sauger, National Geographic

Pointing a wand to the hood, senior project engineer John Bednarchik performs a smoke test to demonstrate wind flow over the body of a 2013 Chevy Malibu, a car for which GM set high goals for reducing aerodynamic drag.

When he heard GM's aim to achieve 0.29 as the Malibu's drag coefficient, Bednarchik recalled thinking, "Well, this is going to be challenging." After all, the model that it was replacing had a drag coefficient of 0.35. To put that in context, the Toyota Prius hybrid (which spent more time in aero testing than any other Toyota model) has a drag coefficient of 0.25, while a 2012 Ford Ranger truck rates at 0.40. (A lower the drag coefficient reflects less resistance, which means less power is needed to move the object.)

(Related Photos: "Cars That Fired Our Love-Hate Relationship With Fuel")

Just a few years ago, Bednarchik said, aerodynamicists believed the shape of a sedan "would really have to change to reach 0.29. You can't go to a designer and say, 'Here's an aero book, design a car.'"

But he said the experts have learned how to improve aerodynamics by refining the vehicle shape and adding elements like underbody panels or active grille shutters that are programmed to close partially or fully based on variables like engine load and vehicle speed. The idea is to reduce air flow under the hood and through the engine compartment, allowing full airflow only when engine cooling or air-conditioning systems demand it.

From 3 to 11 percent of fuel energy is lost to aerodynamic drag, a waste that engineers are working to curb in the aero lab. They position the wheels of a car or clay model carefully on adjustable pads that rest atop risers. Beneath the floor, weigh beams, motors, controls, electromagnets, and levers work together like a supersized, complex version of a doctor's office scale. As wind blows through the tunnel and around the vehicle, the car's weight shifts on the balance, allowing the researchers to measure yaw, pitch and roll, downforce, and lift.

The aerodynamics engineers know they are an integral part of the drive to boost fuel economy. "It's made me feel a lot more important," Bednarchik said. Through his work on the Malibu, the most efficient version of which is rated at 29 miles per gallon, he added, "Personally I saved tons of money and tons of gas."

In total, U.S. regulators have estimated that the new efficiency standards would add $2,000 to the average cost of a new car in 2025, to be more than outweighed by fuel savings of $5,200 to $6,600 over the vehicle's lifetime.

Published August 17, 2012

A Pouch With Power

Photograph by Jeffrey Sauger, National Geographic

GM engineer Douglas Drauch palms one of the 288 lithium-ion cells that together make up the battery pack of a plug-in hybrid Chevy Volt.

Drauch is lead engineer for lab infrastructure and operations at GM's battery systems lab, a facility that just four years ago had only three employees. Today, 40 people—mostly young college grads—work in lab space that has expanded tenfold to 65,000 square feet (6,039 square meters). (Another 25 percent expansion is under way.)

The cell Drauch holds is a pouch, sandwiched between sheets of foam that expand and shrink minutely over wide range of temperature changes. Next comes a thin sheet of metal, with a tiny maze of pin-sized tunnels tracing through it to circulate cooling liquid.

The cost and performance of these cells and packs will dictate the role that plug-in hybrid and all-electric vehicles will play in helping to improve fleet  efficiency. At this point, fully electric vehicles are expected to remain a small fraction of global vehicle sales for the next decade or more—just 15 percent in 2025, by some estimates.

But technology is advancing; battery improvements have boosted the 2013 Chevy Volt's all-electric driving range on a single charge by nearly 9 percent to 38 miles (61 kilometers), while improving efficiency to the equivalent of 98 mpg (42 km/l). The model fell short of its ambitious 2011 sales goal, amid a probe into the model's post-crash battery fire risk. But U.S. regulators concluded there was "no worse fire risk than for gasoline-powered cars," and the Volt has been the best-selling rechargeable vehicle in the United States in 2012.

With the 2013 improvements, the Volt's price tag holds steady at $40,000. Factors such as government rebates, the availability of charging stations, and—of course—the cost of gasoline, will set the price consumers are willing to pay for electric drive. Some of the work under way in GM's battery lab is aimed at driving the cost of energy storage down.

"There is always a small niche of environmentally conscious—and typically more wealthy—buyers that crave energy-efficient vehicles," said Kevin See, a senior analyst with the research firm Lux Research. "But by far the biggest chunk of the market will be those vehicles that don't require major changes in the consumer experience."

Nonetheless, See added, "Better and cheaper batteries create value for all classes of vehicles, from micro-hybrids through full electric vehicles like the [Nissan] Leaf."

Published August 17, 2012

The Magic of the Motor

Photograph by Jeffrey Sauger, National Geographic

This electric motor being tested at GM's power train engineering center in Pontiac, Michigan, is a key component in the drive to 55 mpg.

In a typical passenger car, only about 15 to 20 percent of the energy in the fuel tank actually gets used by the internal combustion engine to move the vehicle down the road. Most of the BTU of gasoline is lost in friction or heat, and some is wasted during idling or deceleration.

(Related: "Supercomputing Power Could Pave the Way to Energy-Efficient Engines")

But electric motors are much simpler than gasoline or diesel engines, with no ignition or compression, no fuel lines, tanks, or exhaust systems. EVs convert about 60 percent of the electrical energy from the grid to power at the wheels, say U.S. government energy analysts. That's one of the reasons why studies have found that a shift to EVs would reduce greenhouse gas emissions, even if a large part of the electric power system is fired by carbon-intensive coal.

And unlike gasoline engines, electric motors provide an opportunity to further drive down emissions. Mitt Romney, the presumptive Republican nominee in the U.S. presidential race, said you can't drive a car with a windmill on it. That's true. But you can charge an EV using wind, solar, hydropower, or nuclear energy to sever carbon emissions from driving.

But the electric motor plays an often unappreciated role in improving efficiency even when it is used in a fossil-fuel-dependent, gas-electric hybrid vehicle. The motor provides a boost of power when needed (for acceleration and passing, for example), helping make it practical to use smaller, more efficient engines to propel full-sized vehicles. That has helped Toyota's Prius hybrid earn a 50-mpg (21.3 km/l) fuel efficiency rating in the United States, and 92 grams CO2 per kilometer in Europe.

Published August 17, 2012

Europe’s Diesel Boost

Photograph courtesy Volkswagen

Volkswagen's turbocharged direct injection engine is an example of the kind of diesel technology that has powered Europe to global dominance in fuel efficiency.

"Europe is expected to lead the world in fuel economy through at least 2015 if not longer, primarily due to the expanded use of efficient diesel engines in its light-duty vehicle fleet," according to the United Nations' Global Fuel Economy Initiative.

The compression-ignition engine developed in 1893 by German inventor Rudolph Diesel has always been more efficient than its gasoline counterpart. While the typical spark-ignited gas engine loses about 80 percent of the energy that goes in as fuel, a diesel engine wastes 40 percent or less. That's thanks to reduced throttling—which shrinks pumping losses—high-pressure direct injection of fuel, and other factors.

Diesel engines of the past produced more pollution than gas engines. But regulators on both sides of the Atlantic have forced refiners to produce a cleaner, low-sulfur diesel fuel, and carmakers have added filtering systems to further reduce emissions.

(Related: "Fat's Chance as a Renewable Diesel Fuel")

Volkswagen says its TDI Clean Diesel technology achieves even more efficient and cleaner combustion due to the way highly atomized fuel is injected directly into the cylinders to mix intensively with cool compressed air. As the U.S. Department of Energy's Argonne National Laboratory puts it:  "If you're buying a diesel car from 2007 or later, it's no dirtier than a gasoline-powered vehicle."

European nations have made a concerted effort to shift drivers to diesel by slapping higher taxes on gasoline; as a result diesel is currently selling about 6 percent less than unleaded petrol in Europe. In the United States, this month, diesel fuel costs about about 7 percent more than gasoline. The higher efficiency of diesel engines would still make it a better deal for the driver, but U.S. automakers have not embraced the technology.

"Diesel, it'll last as long as gas'll last," said Roger Clark, senior manager of General Motors' alternative energy center. "But is it the wave of the future? If we went all diesel here, we'd probably see our market shares tumble."

For future vehicles, Argonne lab researchers are experimenting with using gasoline in a diesel-style engine. And standing in the wings are diesel-electric hybrids, such as the E300 BlueTec Hybrid from Mercedes-Benz and Volvo V60—both planned only for the European market at this point.

Published August 17, 2012

Turbocharged Efficiency

Photograph by Jeffrey Sauger, National Geographic

A metal maze of rounds and tubes, it looks like a small-scale version of the machine that swallowed Charlie Chaplin in Modern Times. But it's GM's 2-liter Ecotec engine, here awaiting testing at the automaker's power train engineering center in Pontiac, Michigan.

Used in the Cadillac ATS, rated at 33 mpg (14 km/l), and the Chevy Malibu, 29 mpg (12.3 km/l), the Ecotec uses a turbocharger and direct injection to deliver as much power as a much larger, thirstier engine.

"There will always be a demand for big, powerful engines, but we will see fewer of these in the future, and those who want them will have to pay a lot,"  says Omotoso, of LMC Automotive.

In essence, turbochargers are a way for engines that are normally like mild-mannered Dr. Bruce Banner to acquire temporarily the superhuman strength of the Incredible Hulk. They do this by forcing compressed air into the engine's cylinders so that each explosion of fuel generates extra power.

According to the U.S. Department of Energy, turbocharging can boost fuel efficiency by as much as 7.5 percent. Combined with direct fuel injection systems—which enable precise control of the fuel as it's injected into the cylinder—the efficiency gain can reach 12 percent.

"What you're always trying to do is keep the engine operating at the most efficient point," said David Lancaster, a technical fellow at the GM power train center. "You might want to be at a certain point, but you can't get there instantly. It's always a transition, and managing that."

Published August 17, 2012

Treading Lightly For Efficiency

Photograph by Jeffrey Sauger, National Geographic

A low rolling-resistance tire waits to take its place on the hub of a Chevy Volt at GM's Detroit-Hamtramck assembly line.

Anyone who has ridden a bicycle with a flat tire knows the feeling of rolling resistance. Underinflated tires deform more and require the cyclist to work harder. In cars, rolling resistance, or the resistance caused by deformation of a tire as it rolls under load, can account for as much as 8 percent of inefficiency in highway driving. Reducing rolling resistance by as little as 5 to 7 percent could boost fuel efficiency by 1 percent.

Improving rolling resistance is not just about proper inflation. Advanced materials and design, such as silica fillers (introduced in the 1990s), also make a significant difference. This is one of the less costly ways to improve fuel economy, and already many vehicles come equipped with the technology. Still, there is room for improvement.

By the 2017 model year, the U.S. Environmental Protection Agency and the National Highway Safety and Transportation Administration (which are responsible for drafting and enforcing U.S. fuel economy standards) anticipate more than 85 percent of new vehicles will have tires that reduce rolling resistance by 10 percent compared to a 2008 baseline. Down the road, further advances in tire materials and design could further reduce resistance to 20 percent below the 2008 baseline.

Published August 17, 2012

Strength in Lightweight

Photograph by Michele Tantussi, Bloomberg/Getty Images

This BMW carbon fiber car chassis, on display in 2010 at the carmaker's plant in Leipzig, Germany, may well be a window into the automotive future.

BMW aims to build one of the first mass-production vehicles relying on lightweight, ultra-strong carbon fiber. By using plastic reinforced with carbon fiber, BMW hopes to shave energy consumption of its new urban electric car, the i3 (previously known as the "Megacity"), to begin production in 2013.

There's nothing quite like a slim-down to help shrink a car's appetite for fuel. It takes less energy to overcome the inertia of a lighter-weight vehicle, and less energy is wasted during braking.

That's why for vehicles of any size, advanced materials such as carbon fiber composites, high-strength steels, magnesium alloys, aluminum (the material of choice for Tesla Motors' Model S electric sedan), and polymer composites could hold the keys to better fuel economy by making vehicles lighter. "Carbon fiber is not new in the industry," said Dan Flores, manager of communications for research and development, global engineering, and advanced technology at General Motors. "But typically [carbon fiber production] has been very low volume and very costly."

The Volt is made primarily of high-strength steel, although the wheels do use aluminum to create a more luxe look without adding excess weight.

Shaving just 10 percent of a car's weight can improve fuel efficiency by 6 to 8 percent. One of the most obvious ways to do this is to simply make a smaller vehicle. As Omotoso noted, "Europeans are already used to small vehicles due to their $7- to $9-a-gallon gas. In the U.S., we'll have to start getting used to smaller cars and trucks, as well as a variety of alternative power trains such as diesel, plug-ins, and electrics."

Because of their boxy profiles, however, the tiniest cars on the road are often less efficient than more aerodynamic compacts-especially in highway driving, when wind resistance comes on strong. And they can be a tough sell without convincing economics. "Consumers are only interested in fuel economy when gas prices are high," Omotoso said. "Otherwise they just want the biggest, most comfortable vehicle they can afford."

Published August 17, 2012

Battery-Pack Abs

Photograph by Jeffrey Sauger, National Geographic

The flat belly of this Chevy Volt on the Detroit-Hamtramck assembly line bulges only with the power packed into its T-shaped lithium-ion battery assembly.

Shedding pounds from the basic design of a vehicle can allow for the addition of advanced emissions controls and heavy battery packs without increasing the total weight. In the plug-in hybrid Volt, the battery pack contributes about 435 pounds (198 kilograms) of the car's total 3,781-pound (1,715 kilogram) weight.

In addition to reducing overall weight, engineers working to boost fuel economy must also look to minimize parasitic energy losses. These losses are just as nasty as they sound, taking a bite of as much as 6 percent bite out of vehicle efficiency. Power steering has long been one of the culprits, but new electric power steering systems in cars like the Volt actually save fuel.

"Electric power steering—the first ones—let's face it, they weren't that good," said Clark. Five or six years ago, he recalled, GM's electric power steering systems were hydraulic. They constantly drew power from the engine to run a pump.

Electric power steering systems, on the other hand, draw power from an electric motor on demand. According to Ford Motor, electric power steering helped improve the fuel economy of its diesel Ford Fiesta (sold in Europe) by at least 3 percent compared to the old hydraulic system.

Published August 17, 2012

No Idle Waste

Photograph by Jeffrey Sauger, National Geographic

This single internal combustion engine cylinder represents opportunity for energy savings.

Strategically deactivating a cylinder like this one being tested at GM's power train engineering center can help shrink the amount of energy wasted in an internal combustion engine.

Some of that waste happens during idling—when the car sits at a red light or in bumper-to-bumper traffic with the engine running. In fact, fully 3 percent of fuel energy is used up needlessly running the engine and powering accessories like the water pump and power steering while the car stands still.

"In order to study the combustion process, you want to take away all the extra hardware and focus on one simple system," Lancaster explained. "We're looking for tenths of a percent everywhere we can get it."

A system known as start-stop or micro-hybrid technology offers a solution. A standard feature of hybrid cars, and already popular in cars with conventional engines in Europe, start-stop systems shut the engine off when a vehicle stops, and restart it upon depression of the accelerator.

Forecasters with Lux Research expect micro-hybrids to get the biggest sales boost due to Europe's carbon emission regulations, reaching global sales of 39 million by 2017. Micro-hybrid technology can save anywhere from 5 to 15 percent on fuel, with only an incremental price increase, "making them much more attractive than more expensive plug-in vehicles," See said.

Lux expects as many as 8 million vehicles on North American roads will be equipped with start-stop technology by 2017. Johnson Controls, which supplies batteries for start-stop systems, anticipates this technology could be found in 40 percent of new vehicles in the U.S. by 2015.

Published August 17, 2012

Regenerative Braking

Photograph by Jeffrey Sauger, National Geographic

This smooth gray disc harvests energy that would otherwise be wasted. It's a regenerative braking system, captured here as it moves through the assembly line at GM's Detroit-Hamtramck plant.

With conventional automotive systems for slowing and stopping, excess energy is lost as heat through the friction of the brake linings. A regenerative brake harnesses that energy to recharge the battery. The frequent braking of city driving means less gasoline consumption for hybrid vehicles like the Chevy Volt and the Toyota Prius.

It all works together as a system, and because the battery in a hybrid is needed for short bursts of power rather than for sustained driving, it can be designed and managed differently (and at lower cost) than the battery for an all-electric vehicle. As GM battery engineer Drauch puts it, "We can hit these a little harder, and they still last for a long time."

Published August 17, 2012

Reaching for Greater Range

Photograph by Jeffrey Sauger, National Geographic

GM lead test engineer Alan Martin glances at the door of a climate test chamber where he has been challenging a Voltec battery with temperatures of -49° F (-45°C).

This type of durability testing in extreme environments helps engineers at GM's battery systems lab in Warren, Michigan, to find the true limits of a battery, with the goal of learning how to eke more miles out of every charge.

For plug-in hybrid models like the GM's Chevy Volt and the Fisker Karma, a greater electric range means less frequent reliance on internal combustion engines. Fuel economy is decidedly modest in the gasoline-powered "range extender" mode; for the Karma, it's as low as 20 mpg (8.5 km/l). The Volt's "range extender" mileage is 37 mpg (15.7 km/l).

(Related: "Range Anxiety: Fact or Fiction?")

According to Drauch, determining the true limits of the battery will be the most important factor in improving the Volt's fuel economy in the coming years.

Two large chambers in the battery lab are dedicated to helping engineers calibrate how much energy the battery holds at any given time. "You don't want to run out of energy, but you also don't want to carry extra weight you never use," says Drauch.

With the Volt, he says, "We kind of over-engineered things. We wanted the Volt to run flawlessly out of the gate."   Because draining a battery to zero can take a toll on its life, GM made sure it was programmed to keep a healthy amount in reserve. But after two years on the market, the carmaker has learned through testing that the Volt didn't require as much buffer as initially thought. So the updated battery management system lets the car demand a little more of the battery before the gas engine kicks in. "We underestimated the durability," Drauch said. "Now we can skinny it up."

At least one thing is already sure: This is only the beginning of the road that leads to fleets of vehicles getting 55 mpg and beyond. "There's always going to be a need to keep improving," said Clark. "There's no one magical alien technology."

Published August 17, 2012

Next: Cars That Fired Our Love-Hate Relationship With Fuel

Photograph from Lambert/Getty Images

Published August 17, 2012