Automotive News - September 22, 2008 - (Page 18)
18 • SEPTEMBER 22, 2008 INSIGHT 4 0 W AY S D E S I G N E R S A R E M A K I N G C A R S A N D T R U C K S M O R E A E R O D Y N A M I C Slippery styling Aerodynamic box One reason boxes are used in vehicle design: They’re an efficient way to carry things. The challenge was making a box aerodynamic, and the designers of the Ford Flex — with its drag coefficient of 0.0355 — succeeded. One way: Block off the top third of the grille to keep unneeded airflow out of the engine compartment. Another Flex tweak: Changes to the rear header radius, where the back window meets the roof, helped lower drag. One more Flex feature: The wind tunnel showed that rounding the taillights more than on the concept model improved aerodynamics. Designers are analyzing modern vehicle bodies like never before, pondering every crease, crevice, gap, nook and cranny — searching for ways to cheat the wind just that little bit more. “We are paying very serious attention to very small details,” says Toyota global design chief Wahei Hirai. Here’s a look at some things stylists are doing to improve aerodynamics. New angle Instead of using rounded front corners, Toyota is moving toward angled corners that provide a flush surface in front of the wheel as on the iQ minicar. The company’s aero experts say this helps to stabilize airflow and reduce turbulence around the car. Toyota calls the treatment the Aerocorner. Toyota plans to seal the upper front grille of future models as much as possible and make the lower grille the main air intake for cooling the engine. That’s because a yawning hole up high causes too much drag. Placing the grille lower streamlines the front fascia and allows designers to make the grille opening smaller — because air pressure is higher closer to the ground. Fin-shaped fairings The Honda FCX Clarity’s aluminum five-spoke wheels have a distinctly performance look to them, but they were designed using fin-shaped plastic fairings to minimize turbulence. Because it must be exposed to the air, the exhaust system has long been a problem for aero designers. How to get around that? Eliminate the engine. Thus, the Clarity fuel cell vehicle can have an almost-flat bottom. Louver, come back Cadillac’s Provoq concept features front grille louvers that close at highway speeds to improve aerodynamics and open at low speeds to provide maximum cooling — in this case, to the fuel cell stack. Roof racks are a problem. You can eliminate them or — as Cadillac did with the Provoq — design a low-drag rack. Under wraps Pickup beds have long been a challenge to designers trying to manage airflow. The 2009 Chevrolet Silverado XFE and GMC Sierra XFE models use a soft tonneau cover to hide the bed. On the Silverado and Sierra XFE models, vehicle height was lowered 18 millimeters, and the front lower air dam was extended 10 millimeters. For pickups, GM may adopt “vortex generators” — essentially, aerodynamic shapes that could be molded into the roof or body panels. That technique is used on airplane wings. FX vents The redesigned Infiniti FX has side air vents that allow air to flow through the engine compartment and out the side of the crossover. Winnowed wells Smaller wheel wells and lower side sills on the 2009 Dodge Ram 1500 pickup reduce drag. Other Ram aero fixes: Flush-fitting pockets for the fog lamps don’t trap air. The wipers are situated lower to reduce wind noise and drag. The raised lip on the cowl screen directs airflow toward the sides of the windshield. A subtle notch near the rear edge of the side mirrors assists airflow. Even flip-up tow mirrors, normally a major source of wind drag, are designed to minimize wind turbulence. A smaller hood opening improves aerodynamics. continued on Page 20 ▼
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