Ways Automakers Can Meet New MPG Standards

http://www.popularmechanics.com/blogs/automotive_news/4218266.html

June 21, 2007
Top 4 Ways Automakers Can Meet New MPG Standards: Detroit Report

First automakers were standing tough. Then they caved in. But after the Senate voted tonight on the stickiest part of the new energy bill, here’s the reality: America is looking at its first big rise in fuel economy standards in decades. After contentious debate on Capitol Hill and lobbying from the industry, new Corporate Average Fuel Economy (CAFE) standards will jump to 35 mpg for all cars and SUVs by 2020, up from the current 27.5 mpg for cars and 22.5 mpg for trucks. Here are four keys for automakers to bolster their fuel economy. One thing is for certain: This is going to be expensive for everyone. —Chuck Tannert

CUT THE FAT

Dramatic mileage gains demand hefty weight losses. The lighter the load, the smaller and more efficient a vehicle’s powertrain can be, so it uses less gas per mile traveled. First, automakers should start using lightweight, yet strong building materials. Most of today’s cars and trucks are made primarily of steel. Switching to aluminum (quite a few Audis and Jaguars already do) and using a few carbon-fiber body panels (like the Corvette Z06 does) could make an immediate—but of course, expensive—difference. And that’s not all. Glass, for example, is one of the heaviest components of an automotive body—a polycarbonate sandwiched between two ultra-thin pieces of glass could replace traditional tempered glass windows, looking the same but weighing about half as much. In addition, reducing the amount of cables throughout the vehicle would save a surprising amount of weight. Given the state of wireless technology, that’s not out of the question.

BUILD A BETTER POWERTRAIN

The quickest way to boost MPG is to improve the efficiency of your powertrain. Hybrids are no-brainers. And someday perhaps we’ll all have hydrogen-powered rides. But there is a more short-term solution that automakers can easily embrace. “With diesel, you can have your cake and eat it too,” says Rob Moran, public relations manager of product and technology for Mercedes-Benz. Diesel engines (like the one we just opened up) burn 30-percent more efficiently than similar sized gasoline engines—i.e., you get 30-percent more mpg. Also, as PM explained in our May cover story, plug-in technology will become more feasible over the next decade as lithium-ion batteries improve in quality and are produced en masse.

KEEP ON ROLLING

For optimum fuel efficiency, tire manufacturers must design tires for minimal rolling resistance. That’s on the horizon. Tires may not get any skinnier, but they will have new compounds that maintain wet and dry weather grip and decrease rolling resistance. Designing a tire inflation system that could vary pressure depending on the conditions could essentially allow on-demand changes in rolling resistance. A study by the Transportation Research Board, commissioned by the National Highway Traffic safety Administration, found that cutting resistance by 10 percent yielded a 1- to 2-percent improvement in gas mileage. There’s a tradeoff, of course: reduced performance.

GIVE 'EM MORE GEARS

This is one of the easiest ways to improve mileage. Manufacturers already have 6-, 7- and now 8-speed transmissions. More gears equal better mileage, especially when the transmission design has double overdrives. Continuously variable transmissions (CVT) should help, too. Normal transmissions only allow a few different discrete gear ratios to be selected, but a CVT essentially has an infinite number of ratios available within a finite range, so it enables the relationship between the engine speed and driving wheel speed to be selected within a continuous range. This can provide better fuel economy by enabling the engine to run at its most efficient speeds within a narrow range. Nissan is already using them in almost every one of its passenger cars.

There’s no question that Detroit can build cars and trucks that meet the new CAFÉ standard. And Congress is determined to make them do it. But has anybody calculated the costs? Raising fleet standards to these levels would add thousands of dollars to the cost of the average vehicle—carbon fiber and polycarbonate don’t come cheap, folks! We appreciate Congress’s effort to grapple with this issue, and automakers need to respond. But raising CAFE standards is a pretty blunt instrument to encourage complex technological change. We suspect that consumers—and voters—may experience something like sticker shock when they realize they’re the ones paying the bill.