Porsche unveils plug-in hybrid 918 supercar

• Porsche says the 918 represents it future
• It will have a V-8 engine and electric motors with batteries
• Porsche promises blistering performance

For three years, Porsche has tantalized with its concept version of a plug-in hybrid supercar, the 918. Now comes the real thing, and what a significant car it appears to be.

The 918 Spyder combines a V-8 engine with two electric motors and a lithium-ion battery. It can run up to 18 miles on electric power alone around town, but when the big engine kicks in, it becomes a monster at the track.

Porsche says it will be accelerate from zero to 60 miles per hour in less than 2.8 seconds using full power -- and 7 seconds using electricity only.

"There are a whole bunch of the hybrid supercars coming, and Porsche's is the most extreme as far as the hybridness goes," says Frank Markus, technical editor for Motor Trend who drove a 918 prototype in Germany. "You drive this thing on a racetrack and (when) you slam on the brakes, it's shoveling a lot of energy back in the battery. The charge went up during my drive."

Porsche says its goal with the 918 Spyder droptop was "the parallel improvement of both efficiency and performance without one being at the cost of the other." It says the 918 Spyder "will act as the gene pool for the Porsche sports cars of the future."

That future, as embodied in this single car due to come to market soon, will not be based on a single new technology, but several. Lightness from a body of carbon-fiber reinforced polymers. Separate electric motors on each axle. The latest V-8 engine that develops 608 horsepower.

When that raw engine power is combined with the electrical output, the result should be 887 horsepower. Top speed: 211 miles per hour, or 93 mph on electric power alone.

Yet, as a plug-in, the 918 is designed to be a pussycat in everyday driving. Its electric range is meant to be enough to make for a decent commuter range. It can be recharged from a standard wall socket in about seven hours.

Between its gas and electric power plants, the end result for the 918 should be amazing quickness. The Porsche 918 Spyder prototype was 20 seconds faster than a Porsche Carrera GT in completing the north loop of the famous Nurburgring race course in Germany.

Why so nimble? To keep the 918 pinned to the pavement, there's a retractable wing to add to downforce. There are also shutters around the headlights that open for cooling at slow speeds and close at high speeds.

Despite the extra weigh of having to tote a hybrid battery, the car weighs only 3,715 pounds. The heaviest components are situated low to give the car more ground-hugging characteristics. Also, the rear axle is steerable to make cornering more precise. The car is all-wheel drive.

"It doesn't feel heavy" when driven, Markus says. And "the engine sound is as feral and wild as any other supercar out there."

Drivers will certainly know: "the exhaust is two feet from your ear," he points out.

Only 918 of them will be built, starting on September 18, or 9/18. When it started taking orders a couple of years ago, the price was $845,000.