If one were to guess which year the U.S. auto industry achieved its highest average fuel economy, it would seem safe to assume that the current crop of cars and trucks met that mark. The reality, however, is that it was 24 years ago. In 1987, cars and light trucks on U.S. roads combined to achieve an average of 26.2 mpg. Since then, consumers have become enamored of trucks and SUVs, pushing the average fuel economy lower.

But for those keen on seeing fuel economy improve, the future is promising — and mandated. By 2025, automakers must achieve a Corporate Average Fuel Economy (CAFE) of 54.5 mpg, nearly double the current 27.5 mpg requirement. Automakers that fail to meet the CAFE standards will be hit with a penalty of $5.50 for every tenth of a mile they fall short multiplied by the number of vehicles they sell. Conversely automakers can be awarded credits for models that exceed the CAFE standard. Those credits can be used to offset penalties.

CAFE is the federal government’s fuel economy standard, conceived as a result of the Arab oil embargo of the early 1970s. The mileage standard does not specify fuel economy for individual vehicles. Instead, it determines the average fuel economy across an automaker’s fleet of cars and light trucks (i.e., pickup trucks, vans and SUVs). The existing CAFE standard was set in 1990, however, legislation signed by former President George W. Bush in 2007 raised the bar to 35 mpg by 2020. In July, the Barack Obama administration went further, revising CAFE to require automakers to achieve 35.5 mpg by 2016 and 54.5 mpg by 2025.

There are many questions associated with the 54.5 mpg standard. How will the standard affect car prices? Will there be a measurable impact on the nation’s dependence on foreign oil? What does this mean for electric and hybrid vehicles? But perhaps the most fundamental and compelling question is how will automakers produce a fleet of vehicles that achieve essentially twice the miles per gallon that they do today?

It’s the Physics

General Motors spokesman Greg Martin started with physics as he aimed to explain how automakers hope to achieve the 54.5 mpg mark. “They are immutable laws,” he said. “That is the beauty of physics.” And Martin, along with virtually everyone else in the industry, said there’s no silver bullet for suspending those immutable laws for automobile engines. Therefore, meeting the 2025 standard won’t happen by way of some heretofore unknown technology or overnight revolution in engine design. Rather, the standard will be met by incremental improvements to existing engine systems.

“It is not just going to be one thing, but a compilation of things that will get us there,” Martin said. “Keep in mind that there is also a competing set of regulations that automakers have to comprehend [regarding] safety. All of those safety systems, both active and passive, add weight and mass to the car. This is what makes the industry and business so challenging but fascinating at the same time.”

Despite the surge in hybrid vehicles and new all-electric cars like the Nissan Leaf, most industry observers predict that the internal combustion engine has a long life ahead of it. So those engines will need to achieve far better fuel economy than they do today.

Sandeep Sovani, the resident auto expert at engineering simulation software firm Ansys, said there are two components to boosting fuel economy for internal combustion engines: increasing their efficiency and reducing their need for fuel.

Efficiency gains will come from greater use of turbocharging and systems that shut down some of an engine’s cylinders when they’re unneeded, Sovani said, along with vastly improved transmission technology. To cut energy requirements, and therefore reduce the need for fuel, automakers will pay more attention to aerodynamics and weight reduction.

“Over the next 10 years or so, aluminum content in the car is going to increase significantly while steel content is going to shrink,” he said. “And composite materials can be used in many places instead of metal.”

In November, Bosch Corp. invited members of the media to the Power of Innovation event at the company’s Plymouth, Mich., engineering, research and development facility. Bosch, a German multinational engineering and electronics company, makes everything from cordless drills to washing machines. But Bosch’s primary products are automotive components, which the company designs and sells to most major auto manufacturers. At the event, engineers and executives from the company explained how automakers will meet the stricter CAFE requirements.

By 2020, Bosch CEO Peter Marks said there will be a market for 103 million new vehicles, but only 9 million of those will be hybrids or all-electric. Consequently automakers will rely largely on innovation in the design of gas and diesel engines.

“Getting to 54.5 mpg must be done using a proper mix of technologies,” Marks said. “It requires us to look holistically at vehicle improvements,” adding that Bosch “engineers are excited by the untapped potential of technology” to meet the standard.

Bosch engineers explained the various elements of an automobile that they and others are working on to improve performance. None of these components in particular will lead to dramatically higher fuel economy, but when operated in concert, these elements should yield a corporate average fuel economy of 54.5 mpg or more.

Gasoline Direct Injection (GDI): Many manufacturers, including Bosch, are investing in this technology. In a traditional gasoline engine, fuel and air are mixed in the intake manifold prior to being injected into the cylinder, where it is ignited by a spark plug. The explosion forces the piston downward, thus generating power. In a GDI system, a computer-controlled, high-pressure injector dictates the precise amount of fuel to inject directly into the cylinder. The timing and spray pattern of the fuel injection are also computer-controlled, resulting in a more complete burn than can be achieved in existing engines. The more efficiently fuel is burned, the better the engine’s fuel economy. The cost and complexity of GDI systems have kept the technology from becoming common, but CAFE seems poised to make GDI standard in the coming years.

Turbochargers: These have long been viewed as options for car owners who are speed and performance enthusiasts. But increasingly, they are getting a second look as a way to make small engines perform like big ones while maintaining high fuel efficiency. Turbochargers work by using exhaust gases to power a compressor that delivers more air to the engine, which in turn generates more power and better fuel efficiency from an otherwise normal engine. The Ford EcoBoost engine, for example, combines a turbocharger with GDI to deliver up to 20 percent better fuel economy and up to a 15 percent reduction in emissions while improving overall engine performance.

Clean Diesel: Long associated with dirty, smoky cars, diesel is experiencing a rebirth. By 2013, at least 15 new vehicles from a host of manufacturers will feature diesel engines. Modern diesel engines use “clean diesel” fuel, which is the common name for ultra-low sulfur diesel. Clean diesel, according to Bosch, delivers 30 percent better fuel economy than gasoline engines and 25 percent less carbon dioxide emissions. Bosch also states that since 1990, overall emissions from diesel have been reduced by 95 percent. Diesel engines have been more fuel efficient than gasoline engines because the fuel in diesel engines is ignited in the cylinder by compression instead of a spark plug, which requires a richer mixture of fuel and air.

It should be noted that Bosch has a significant stake in diesel technology as it is a German company and diesel is more commonplace in Germany. But data from the U.S. Coalition for Advanced Diesel Cars — of which Bosch is a member — supports the company’s conclusion. As stated in a white paper from the coalition: “Switching from a gasoline engine to an advanced diesel engine (turbocharged with exhaust after treatment) will improve fuel economy up to 30 percent and reduce [greenhouse gas] emissions as much as 25 percent, at an additional cost of $1,500-$2,000 per vehicle. In the last 20 years, turbochargers have overcome [a] traditional drawback of diesel engines — sluggish engine response — and have greatly improved the driving experience.”

Start/Stop Systems: When an engine isn’t running, it does not use any fuel — that’s the idea behind this technology, which owners of hybrid or electric vehicles already experience. When coasting to a stop sign or waiting at a stoplight, the engine shuts itself off. These systems are more difficult to apply to internal combustion engines, where auxiliary components like air conditioning and water pumps often operate on a belt system that depends on a running engine. Furthermore, the engine starter mechanism was seen to be at risk from the dramatically increased number of engine restarts. There’s also the problem of alternators, which use engine power to generate electricity to operate other engine components. If the engine is off, those components depend entirely on batteries. Bosch is developing advanced starter mechanisms that can handle the stress of multiple engine restarts while incorporating better batteries and regenerative braking to keep componentsoperating with the engine off. Additionally electric motors can be used in place of serpentine belts to allow components to operate without engine power. Bosch estimates that start/stop technology can reduce a vehicle’s fuel consumption by 10 percent.

Electric Power Steering: How can power steering affect a car’s fuel consumption? Like most other components in modern automobiles, power steering systems draw power from the engine to operate the hydraulic mechanisms needed for power steering. In many cases, power steering is a dumb system, meaning it draws power from the engine continuously, whether the system is in use or not. This places a heavy load on engines that requires more fuel consumption. Adding intelligence to the system can yield significant improvements. Most power steering systems today are either purely hydraulic or electronic-hydraulic, which uses an electric motor to pump hydraulic fluid through the system. Electronic-hydraulic systems use only 20 percent of the power that a traditional hydraulic-only system does. Fully electronic power steering dispenses with hydraulics entirely and draws less than 2 percent of the power that a traditional power steering system would. And electronic power steering is on demand, so almost no standby power is required. Electronic power steering can add 10 percent efficiency to each gallon of gas an equipped car consumes. It also reduces engine complexity and simplifies manufacturing.

Better Electric Motors: Like electronic power steering, advanced electric motors for other components in a car can help reduce the load on an engine and therefore reduce the engine’s fuel consumption. Cars made today have on average about 35 electric motors that power various components, such as windshield wipers, lighting and seat adjustment. Engine cooling, air conditioning and power steering are the biggest power users. With improved engineering in the design of these motors, efficiency is being increased while size and weight are being decreased. Engineers at Bosch said that in the coming years, the number of electric motors in cars will grow from 35 to more than 50 in small cars. These changes will further reduce weight and power consumption, leading to more gains in fuel efficiency. In addition, these electric motors take up much less room in the engine compartment compared to traditional component systems, allowing engineers to make better use of available space. More space to design can lead to more aerodynamic cars, further adding to efficiency gains.

So while there likely won’t be a day that the world wakes up to a brand-new propulsion system that changes everything, GM’s Martin thinks very soon we will suddenly realize how much better our cars have become.

“The years will lapse and there will continue to be incremental progress that we won’t notice, until maybe in 10 years we look back and say, ‘Oh my gosh, the car I’m driving gets X mpg compared to cars from today.’ It will be gradual, yet [CAFE] is aggressive, and with any good agreement, it really pushes the hell out of us. Everybody can find something to like in it [or] something not to like in it — and in this day and age that is a rare occurrence in Washington, so we will see what happens.”

Chad Vander Veen  |  Associate Editor