Error 404--Not Found

From RFC 2068 Hypertext Transfer Protocol -- HTTP/1.1:

10.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent.

If the server does not wish to make this information available to the client, the status code 403 (Forbidden) can be used instead. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address.

Error 404--Not Found

Error 404--Not Found

From RFC 2068 Hypertext Transfer Protocol -- HTTP/1.1:

10.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent.

If the server does not wish to make this information available to the client, the status code 403 (Forbidden) can be used instead. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address.

Global Viewpoints
GM's PNGV concept sedan


Development of GM's PNGV concept car involved the first comprehensive use of the automaker's proprietary shape development software with neural networks, which allowed evaluation of shape ideas more quickly.

Development of General Motors' Partnership for a New Generation of Vehicles (PNGV) concept car is the first comprehensive use of the automaker's proprietary shape development software with neural networks. The software was "trained to understand consequences to the aerodynamics of different surface shapes, which allows you to keep evaluating more ideas, more quickly," explained V. Sumantran, Lab Group Manager at GM's research and development center. Other aerodynamic assessments entailed math-based computational fluid dynamics (looking at six shapes) as well as wind-tunnel tests on six 1/10-scale models; wind tunnel tests on one-third scale models (five sessions, each with a refined surface); five modified EV1 test mule wind tunnel sessions; and 10 full-scale-model sessions.

"The total wind tunnel time was 160 h — half dealing with shape and features, and half dealing with rear thermal system development," said Mike Kutcher, Team Leader and Engineering Group Manager at GM Advanced Technology Vehicles. GM's PNGV concept four-door sedan scores a 0.163 coefficient of drag, besting the production record-holder EV1 coupe's Cd of 0.19. "The aerodynamics achieved on this program was just astonishing, and equates to a 12 mpg increase for this highly efficient vehicle compared to today's midsize sedan," Kutcher said, noting the 12 mpg increase is a composite highway/city number.

After a 10-month research and development to final wind tunnel test timetable, the sedan earned a CdA (drag coefficient x frontal area) of 0.332; a CdBar (average) of 0.180; and a frontal area of 2.034 m2 (21.9 ft2).

Design features contributing to the aerodynamic performance are a rear engine layout, a flat underbody, an electronic rear vision system, and the aforementioned rear thermal system.

Instead of outside side mirrors, the car uses tiny cameras — a set-up similar to that seen on the Cadillac Evoq concept car unveiled at the 1999 North American International Auto Show. "We knew we couldn't afford the 30 counts of drag, so we went with camera mirrors," said George Claypole, Vehicle Integration Engineer for GM's Advanced Technology Vehicles.

The rear thermal system draws air in through quarter-moon-shaped intakes aft of the rear wheels. (There are no intakes on the front end.) Air flowing through the radiators and intercoolers is exhausted via an outlet located between the taillights.

The basic shape of GM's PNGV concept car had a Cd of 0.15 without exterior features such as joints/seams and rear thermal inlets/outlets.

"It's very hard to point to any single item being the dominant aerodynamic factor. It's the combination of details when they all work together," explained Sumantran.

Once the vehicle hard points were established, more than 12 designs were reviewed. The widest area of the vehicle is the front one-third. "It does not turn out to be the aero-potato. This is very modern, aggressive styling," said Ron York, Director of GM's PNGV. Vehicle design and engineering work involved Advanced Technology Vehicles, the Aerodynamic/Thermal/HVAC Engineering Center, GM Research & Development, and GM's design staff.

The concept car is a parallel electric hybrid with a turbocharged diesel engine. The first physical vehicle viewing will be at the 2000 North American International Auto Show in Detroit. DaimlerChrysler and Ford also are slated to unveil PNGV concepts at the NAIAS.

PNGV, a partnership formed in 1993 by GM, Chrysler, Ford, and the U.S. government, targets development of midsize sedans that achieve 80 mpg. Production PNGV prototypes are due in 2004.

Kami Buchholz

Error 404--Not Found

Error 404--Not Found

From RFC 2068 Hypertext Transfer Protocol -- HTTP/1.1:

10.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent.

If the server does not wish to make this information available to the client, the status code 403 (Forbidden) can be used instead. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address.