Hybrids aren't the only way to get more m.p.g.

By Jim Mueller, Special to the Tribune. Tribune auto reporter Jim Mateja contributed to this story
Published September 24, 2006

Mention fuel economy and the talk turns to gas/electric cars and trucks, the hybrids that can top 50 m.p.g. in city driving.

Not far behind are hydrogen fuel-cell vehicles, the technology of tomorrow that promises water vapor as the only tailpipe emission. They got a boost when BMW announced last week that it is putting the system in a 7-Series car.

Both are solutions to the problems of whipsawing gas prices, dependence on foreign oil and air pollution. But they are not the only ones. More modest, and some would say more practical, efforts are ongoing.

Dave Hermance, executive engineer with Toyota's Advanced Technology Vehicles, said consumers can expect increases of 5 percent in miles per gallon as engines are further refined.

Hermance pointed to advances such as dual variable valve timing and direct injection technology, where fuel is burned better to squeeze more energy from each drop of gas.

"There is a 5 to 7 percent fuel economy benefit in cars like Lexus and Avalon with dual VVT," he said. "And direct injection allows leaner combustion. The challenge there is holding the emissions line, managing exhausted NoX [nitrogen oxide levels]."

Then there are more efficient automatic transmissions--those with six speeds or continuously variable systems that allow an infinite number of gear ratios--so engines don't work so hard to maintain highway speeds. Fuel savings? Another 2 to 4 percent, he said.

"Improved aerodynamics and mass reduction are other ways to increase fuel economy," Hermance said. "Taking weight out of the car by using more aluminum and carbon fiber--but those are expensive materials. We're also paying attention to underbody airflow and the frictional loss in bearings. Weight counts when you're accelerating. Friction matters when cruising." Reduce both and boost fuel economy.

Toyota's work on hybrids, a segment in which it is a leader, continues too. "We are making the systems smaller, more powerful and more cost effective," Hermance said.

Dave Lancaster, a General Motors technical fellow for his experience and expertise in engineering, talked along the same lines. But Lancaster stressed the entire vehicle even more.

"Powertrains generate energy," he said. "We also need to consider energy losses: The mass of a car and brake drag and tire and wind resistance. Properly inflated tires and a correct alignment do benefit gas mileage."

Fuel injection has better controlled the way gas is burned since hitting its stride in the 1970s. "Direct injection, which we now have in the [Pontiac] Solstice and [Saturn] Sky, permits us to run a higher compression ratio," Lancaster said. "The engine breathes better."

Lancaster mentioned the 5.3-liter Vortec V-8 as an example of GM engineers tweaking technology to improve mileage. That's the engine with cylinder deactivation that goes from 8- to 4-cylinder operation when optimal.

"There's considerable fuel savings," he said. "I took a [Chevy] Suburban a few weeks ago to drive my daughter to college and the fuel economy display showed 23 miles per gallon keeping it at 70 to 75 miles per hour on V-4 mode." A Suburban, he noted, is EPA rated at 15 m.p.g city/21 m.p.g. highway though he pointed out that the cylinder deactivation makes a direct comparison less precise.

As for hybrids, Lancaster touts GM's development of different systems for various vehicles: a two-mode introduced in transit buses and adapted to pickups and SUVs and another that provides a battery boost at takeoff.

This is in keeping with CEO Rick Wagoner's take on the technology.

"We try to plan a variety of scenarios over a variety of [gas price] levels. When it gets to a $4.50 to $5 a gallon scenario, the hard part is planning how much production capacity you need for hybrids, how much do you ramp up diesels, how many 4 cylinder engines do you substitute for V-6s."

Mark Chernoby of DaimlerChrysler's Advanced Vehicle Engineering Group echoed Hermance and Lancaster, and tossed in the benefits of diesel engines. "Customers don't all come in one size," he said. "Drivers can expect 30 percent better fuel efficiency driving a diesel. And there is a place for diesels in the U.S. market."

Citing their 40 percent market penetration in Europe, Chernoby points out that diesels are not slow and smelly anymore.

"Our challenge is getting that message across, while building the diesel engines that meet stricter U.S. emissions requirements."

And Chernoby's not talking biodiesel, or E85 for that matter. "E85 and biodiesel are more about reducing dependence on foreign oil" than improving mileage, he said. "E85 provides less energy than gas and gets less mileage."

He acknowledged that city drivers tend to benefit the most out from hybrid, but carmaker have to go beyond that.

"Longer term, we will need to move away from oil-based engines toward hydrogen," Chernoby said. "That's when you'll see significant jumps in fuel efficiency."