Porsche hopes to bolster its bottom line with the 2010 Porsche Panamera.

Imagine a 911 with rear doors and a back seat. That's the Panamera, Porsche's first sedan. It should be as special as any Porsche, so it won't be cheap or plentiful.

What We Know About the 2010 Porsche Panamera

Porsche is readying its first four-door sedan to challenge the swoopy Mercedes-Benz CLS and an expected new flagship BMW based on that company's recent CS concept. Called Panamera, Porsche's fourth model line is slated to bow at the early-2009 Geneva Auto Salon in Switzerland. U.S. sales begin several months later for the 2010 model year.

The 2010 Porsche Panamera borrows some components from Porsche's Cayenne SUV, and has a similar mission in life. Porsche conceived the Cayenne to bolster its bottom line and supplement its traditional sports-car business, where sales swings tend to be more severe than in the SUV segment. Though Porsche purists greeted it as heresy, the Cayenne has done just what Porsche intended. As a result, this small, independent company is now the most profitable automaker in Europe. One of the most influential too, as it's also the largest shareholder in Europe's largest automaker, Volkswagen AG. Porsche relies on VW for Cayenne components and production, and wanted to protect those assets by insuring that VW could never be a takeover target, however remote the prospect. Now that's done, and Porsche can diversify its lineup even further, starting with the Panamera.

Spy photos of late prototypes show the Panamera to be a low-slung "four-door coupe" like the Mercedes CLS, but looking like a stretched version of Porsche's flagship 911 sports car. The engine is up front, where it should be in a high-dollar sports sedan, and the sloped tail incorporates a liftgate, a novelty in this class. The Panamera should be a bit smaller and lighter than the CLS, and in line with promises of Porsche-level performance and handling.

Performance should be plentiful, thanks to a pair of Cayenne V-8s. The mainstay 2010 Porsche Panamera S gets a 4.8-liter unit expected to deliver 400 horsepower, 0-60 mph in about 4.5 seconds, and 180 mph all out. An uplevel Panamera Turbo version is tipped to pack some 520 horsepower, enough grunt to challenge the BMW M5 and Mercedes CLS AMG 63 for the title as world's fastest sedan. Both models will offer a six-speed manual transmission and a seven-speed sequential manual. The latter is a new Porsche-designed twin-clutch unit with automatic shift mode, similar to VW's DSG transmission. Those choices should also apply to an expected base Panamera using a VW-sourced 3.6-liter V-6, tuned for around 300 horsepower.

The 2010 Porsche Panamera will launch with rear-wheel drive, but there's talk of an all-wheel-drive option, again based on Cayenne components, arriving in the second or third year. There will also be a gas-electric hybrid model, but details are sketchy when it will be available. Porsche says it will be a full parallel hybrid--meaning it can run on electric only, gas only, or a combination of the two.

Other details are hazier, but it's probably safe to assume the 2010 Porsche Panamera will also draw on Cayenne for suspension components, brakes, and steering. Another safe bet is Porsche's alphabet soup of stability- and ride-enhancing electronics, including an air suspension. Ceramic brakes, borrowed from high-end 911s, may be optional for the Turbo, and all models should include a 911-type rear spoiler that powers up and down according to road speed. Equally predictable, the Panamera will offer all the goodies expected in high-end cars, plus Porsche's usual bewildering array of custom trim options.

Porsche plans to build 20,000 Panameras per year for worldwide sale, with only 9000 or so here in the United States.

The Panamera may be Porsche's first production sedan, but it's not the first four-door Porsche. Back in 1988, Porsche studied the feasibility of a larger 911 with project 989, basically the normal two-door coupe sports car with an extended wheelbase making room for a pair of rear doors and a proper back seat. A single prototype was built but never publicly shown, let alone acknowledged. The 989 remained only a rumor until some years later, when researchers uncovered photographs. The project didn't get far anyway, due to Porsche's deteriorating financial situation at the time, but it appears the 989, had it been produced, would have retained the 911's signature rear-engine configuration.

Buying Advice for the 2010 Porsche Panamera

Aside from hefty cash, you'll need to be on good terms with a dealer to buy a 2010 Porsche Panamera. Porsche plans to build only 20,000 per year for worldwide sale, with perhaps 9000 or so earmarked for the U.S. That may not be enough to satisfy initial demand, so an early order with a hefty deposit might be well advised.

2010 Porsche Panamera Release Date: As noted, the 2010 Porsche Panamera premieres at the 2009 Geneva Salon in Switzerland. Barring any last-minute delays, U.S. sales should begin that fall, and certainly no later than the first quarter of calendar 2010.

First Test Drive: If all goes well, we'll get to try the 2010 Porsche Panamera in spring or summer of 2009.

2010 Porsche Panamera Prices: One British source reports the base 2010 Porsche Panamera will start around $108,000-in today's dollars, mind--and the line--topping Turbo at $168,000. Similar money buys Mercedes's new CLS AMG 63, a Bentley Continental Flying Spur, or Maserati Quattroporte.

For more inside information on hundreds of new cars of today and tomorrow, check out:

• Consumer Guide New Car Reviews and Prices: Road test results, photos, specifications, and prices for hundreds of new cars, trucks, minivans, and SUVs from the Auto Editors of Consumer Guide.
• 2007 Porsche Cayenne: Read Consumer Guide's full report, including ratings, prices, specifications, and fuel economy.
• Premium midsize cars: The Porsche Panamera will compete in the premium midsize-car class. Here's Consumer Guide's roundup of all the premium midsize cars on sale today.
• Fuel-economy leaders: The EPA admits its fuel economy numbers are estimates. Ours are real. Here are the fuel-economy leaders as determined in Consumer Guide tests.