Great news greenies. Porsche will release the new Porsche Cayenne S hybrid in 2010. Despite being able to go 0-100 km/h in under seven seconds, the company claims it will have the same fuel economy as a four-cylinder. Porsche says they will use a similar system on the new Porsche Panamera hybrid after the model is officially introduced.

Unfortunately, Porsche did not reveal the exact efficiency details for their car. However, they anticipate the car will be officially rated at using less than nine litres of fuel per 100 km, or about 26 mpg (US) combined.

Here's what we do know. The Cayenne S Hybrid will use a full hybrid system, with an electric motor capable of getting the vehicle up to 86 mph (138 km/h) without using the combustion engine at all. Porsche claims this lets the vehicle coast as most highway speeds on battery power only, helping to cut down on emissions and increase fuel economy.

Also good news is that Porsche says the hybrid powertrain barely affects the design of the Cayenne. They installed the system without compromising interior and luggage space.

The vehicle uses a supercharged 3.0-liter V6 from Audi. The direct injection engine features 333 horsepower and a maximum of 324 ft-lb of torque. Its hybrid partner is a three-phase synchronous electric motor that dishes out 52 hp and 221 ft-lb of torque. The motor doubles as the alternator, and gets its juice from a 38 kW NiMH battery that weighs in at 154 lbs (70 kg).

Porsche states the battery fits into the spare tire well, but they do not mention if they had to ditch the spare tire to get the job done.

Porsche claims that the "Cayenne S Hybrid is expected to emit some 20 percent less C02 than comparable combustion engine vehicles with similar power output." This is due to the three hybrid settings utilized by the car: combustion engine and electric motor together, engine only, and electric motor only. The automatic transmission triggers engine ignition within 300 milliseconds of the driver's tap on the accelerator. When the engine is running, it sends a recharge to the battery, as do the regenerative brakes when the vehicle is slowed down.

Porsche has made use of an eight-speed automatic transmission for the car, but the top two gears are just icing on the cake. The Cayenne S Hybrid reaches its top speed in sixth, and makes use of the seventh and eighth gears to decrease RPMs, bringing another increase in fuel economy.

Gallery: Porsche Announces Cayenne S Hybrid in 2010

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