- - Thursday, September 8, 2011

As gas prices fluctuate and consumers demand roomier, fuel-efficient passenger cars, aerodynamic design is an important contributor to saving money at the

pump. Preproduction models of the all-new 2013 Malibu are achieving a drag coefficient comparable to a Corvette and nearly as efficient as the Volt electric car.

In fact, aerodynamics help the new Malibu Eco achieve the best-ever fuel economy of a Chevy midsize car. The Malibu ECO with fuel-saving eAssist technology is expected to achieve an estimated 26 mpg city and 38 mpg highway based on GM testing, while an all-new 2.5L Ecotec engine debuting on the Malibu next summer is expected to achieve more than 30 mpg on the highway, based on GM testing.

Aerodynamic design efficiencies and a new body style helped engineers shave 60 counts of fuel economy-robbing wind drag from the model it replaces, the equivalent of adding up to 2.5 mpg more highway driving range.

The new Malibu’s Cd rating of .29 - the number used to indicate the aerodynamic drag force on a vehicle - is down from the current model’s .35 Cd. The higher the number, the greater the drag force a vehicle’s engine must overcome at any road speed. The Volt has a .28 Cd.

“With the new Malibu, the design and aero teams collaborated to achieve maximum fuel efficiency for our customers without compromising the car’s visual appeal,” said John Cafaro, Chevrolet Malibu exterior design director. “The aero and aesthetic evolved simultaneously - working together, we sculpted the car in a way that makes it more slippery, applied innovative technologies like eAssist and active shutters, and we intentionally designed components such as the rear deck lid and outside rearview mirrors to help maximize fuel economy.”

Malibu aero engineers and designers conducted more than 400 hours of wind tunnel testing to ensure optimal fuel economy. In addition to saving fuel, the 2013 Malibu’s new shape, dimensions and sculpted forms reduce cabin noise, another priority for midsize car buyers. On top of a lower coefficient of drag, the new Malibu has a 4.5-inch (114 mm) shorter wheelbase and 62-inch (1,574 mm) front and rear tracks that are more than 2 inches (51 mm) wider than the model it replaces.

“Aerodynamics is driven by science.” said John Bednarchik, Chevrolet Malibu lead aerodynamic engineer. “While car designers favor wheel flares, sharp creases and other details that add style to a car, what catches the eye may disrupt the airflow, creating unwanted air turbulence and increasing drag. The new Malibu balances design needs with aerodynamic efficiency to truly benefit the customer.”

For the first time on a Chevrolet midsize sedan, Malibu LT and ECO models feature active aerodynamics, which change body surface geometry on one or more parts of the vehicle.

Malibu’s active aerodynamics includes a pair of louvers, or shutters, in the lower grill opening of the front fascia. They open or close automatically to maximize aerodynamic efficiency. This increases airflow in certain conditions, such as high-engine loads at low speeds, while the shutters remain closed as often as possible to reduce aerodynamic drag.

While some active aerodynamics merely activate when traveling above or below certain speeds, the aerodynamic shutters in the Malibu have a GM proprietary algorithm that monitors several variables in real time - including engine load, vehicle speeds and ambient temperature - to determine if the shutters should be opened or closed.

When ambient temperatures fall below freezing, the active shutters operate in “ice mode.” By working with a thermometer that monitors outside air temperature, the ice mode will prevent movement of the aero shutters until ambient temperatures rise above the freezing mark. Sensors work with onboard computers to calculate when the ice mode is appropriate.

Four underbody panels - two in the mid-body area under the floor pan on either side of the center tunnel, and two in the rear area covering the fuel tank and rear area on either side of the exhaust - deliver about 10 counts of aero benefit. Constructed of black composite with wind-surfacing, the panels cover approximately half of the underbody. Underbody panels are more commonly found on premium-priced offerings and race cars.

“The underbody panels contribute significantly to the overall aerodynamic performance of the new Malibu,” said Bednarchik. “Customers will never notice the difference, until they check their fuel economy.”

Measured as 0.001 coefficient of drag, a “count” is a precise measurement of aerodynamic drag generated by a vehicle. Reducing aerodynamic drag reduces the energy wasted overcoming pressure drag - due to the difference in pressure in front of and behind the vehicle - and improving overall efficiency.

Vehicle aerodynamics remain a primary driver of overall fuel economy, especially at highway speeds. “Roughly 60 percent of the power used at highway speeds is used to overcome air resistance,” said Malibu aerodynamic engineer Suzanne Cody.

The 2013 Malibu is expected to be among the first cars in the industry to be tested under J2881, the Society of Automotive Engineers’ (SAE) new recommended test procedure for aerodynamic reporting. Under these new industry guidelines, automotive manufacturers will follow a recommended procedure for measuring and documenting the aerodynamic performance in a full-scale wind tunnel of passenger vehicles. Similar SAE procedures for assessing and reporting horsepower and torque are already in place.

The new Malibu will be sold in nearly 100 countries on six continents. It is available in LS, LT, ECO and LTZ models in North America. Malibu production in the United States begins in early 2012 with the ECO model. Malibu will be built in multiple locations around the globe, including the Fairfax, Kan., and Detroit-Hamtramck assembly plants in the United States. Pricing is scheduled to be announced later this year.

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