MPG now! Automakers race to boost efficiency
'Automotive News' reports on efforts by automakers to increase fuel economy.
DETROIT -- During the 18 months he worked on a new version of the Chevrolet Cobalt, Mike Danowski saw consumer tastes change before his very eyes.
When he started, studies showed that styling was the No. 1 reason people bought Cobalts. By the time the vehicle rolled out, fuel economy had leapt to the top of the list, the Cobalt XFE project manager says.
The Cobalt team's timing couldn't have been better.
A combination of revised gear ratios, engine recalibration, and low-rolling-resistance tires improved highway fuel economy 9 percent, from 33 miles per gallon in highway driving for the base Cobalt to 36 mpg for the XFE.
When the Cobalt XFE hit the market in March, consumers applauded. The XFE accounts for about 8 percent of Cobalt's sales volume. "We thought it would be in the 2 to 3 percent range," says Chevrolet spokeswoman Nancy Libby. She says dealers have an 18-day supply of XFEs, the fastest turn of any Cobalt version.
Across the automotive world, designers and engineers are bending sheet metal, trying new tires, tweaking power trains, and performing automotive liposuction to eke out better mileage.
Huge changes will be needed in the future, but many are years away. Carmakers need better mileage today.
The top candidates for near-term improvement:
-- Better aerodynamics. Seemingly minor changes can make air flow more smoothly around a car.
-- Adjust engines. After decades of tuning the computer chips that govern engines for performance, engineers now favor fuel economy.
-- Lose weight. Even tough-guy trucks are dropping rugged steel hoods for aluminum ones.
Take the Ford Flex; based on the boxy Fairlane concept, it was never going to be aerodynamically slippery.
After the Fairlane's positive reception on the auto show circuit, Ford had decided to keep the same basic look.
"From an aerodynamic standpoint, that really limited what we could do," says Wayne Koester, a Ford aerodynamic development engineer. "We couldn't change the shape of the roof or the sides because that's what made this a Flex--the boxiness."
So, designers and engineers focused on tweaking the details, such as squaring up the front fascia and "finessing" the rear corners.
Fairly minor tweaks reduced drag enough to improve fuel economy by one mile per gallon in highway driving.
The Flex has a coefficient of drag--a measure of a vehicle's air resistance--of 0.355. For competing vehicles, Ford says, the number is 0.375. Lower drag brings better fuel economy.
"Aerodynamics is one of the best ways" to boost fuel efficiency, says Richard Gresens, Flex chief designer. "If I'm going to change something a little bit on the sheet metal, and it gives me a little better aero co-efficient--hey, let's do it."
Tweaking the Hemi
Ralph Gilles, chief designer on the 2009 Dodge Ram, and his team turned to aerodynamics to boost the pickup's mileage. An associate says Gilles has made aerodynamics a "religion" in Chrysler LLC's design department.
The truck, redesigned for 2009, emerged from more than 200 hours in a wind tunnel with a coefficient of drag of .419 for the Ram 1500 Crew Cab 4x4. That compares with a coefficient of .463 for the 2008 Ram Quad Cab 4x4. For some pickups, coefficient of drag can be 0.5 or higher.
Chrysler engineers also tweaked the Hemi engine's cylinder cutoff system so it operates in a wider rpm range, enabling the vehicle to run longer in four-cylinder mode.
"There's more torque in the four-cylinder mode," says Mike Cairns, Ram chief engineer. "So you're able to propel the vehicle in four-cylinder mode more often."
Also, compression is up, and the efficiency of air and fuel flowing through the engine has been improved. The Hemi added the fuel-saving feature of variable valve timing, which changes the time the valves open and close to let the engine run at peak efficiency.
Then the pickup went on a diet. Engineers cut out 80 pounds, which might not seem like much on a 6,700-pound vehicle. But the weight loss, engine tweak, and improved aerodynamics combined to achieve a one mile per gallon improvement in fuel economy. That may seem paltry, but as Chrysler spokesman Bryan Zvibleman says, "We're fighting for every mile per gallon in this ultracompetitive segment."
Little changes add up, says Derrick Kuzak, Ford group vice president of global product development. He says he tells his team, "We need to treat every joule of energy in a vehicle like a precious commodity."
That means improving "every element of a vehicle, whether it's aero, rolling resistance, power train," driveline efficiency, or energy drains that don't move the vehicle, such as power windows or heated seats, he says.
"All of those, we're working on. We benchmark. We're improving."
Amy Wilson and Jamie LaReau contributed to this report.
(Source: Automotive News)