Porsche has always been a purist when it comes to building sports cars. Still is. However, the German automaker has recently had to expand its famed “There is no substitute” design philosophy to remain competitive in the global market, as well as to satisfy those pesky government regulators, both here and in the homeland. Don’t worry: The company will continue to craft blindingly fast, nimble machines for your driving pleasure. Only now, it will also offer them — or some of them — with diesel and hybrid powertrains as well.

The first Porsche diesel, in its Cayenne SUV, recently went on sale in Europe. And in late 2010, will bring to market its first hybrid powertrain.“If you want to grow, you have to enter new segments,” said Klaus-Gerhard Wolpert, Porsche’s director of Cayenne operations. “We are strongly convinced we can reach a business case with this system.”

While the diesel Cayenne won’t make the trip to this side of the pond any time soon, Porsche will bring its first hybrid-powered vehicle stateside in late 2010.

Why Hybrid?

It’s no secret that hybrids have gained popularity in the U.S. With this in mind, Porsche’s board of directors began looking into developing a hybrid system by first driving the competition to see if the idea would fit with Porsche’s fun-to-drive character. They decided that hybrid driving has a fun factor all its own, and that adding the fuel-sipping technology into the company’s mix of high-performance machines would satisfy both its desire to be socially responsible and ever-changing European and U.S. environmental legislation. Plus, the automaker’s loyal customers might just love the tax incentives.

Coincidentally, , which had worked with Porsche on the Colorado Project (which became the Cayenne and VW Touareg), saw a need for a hybrid as well. So, the two companies paired up. The project began in earnest in 2006, when Porsche and Volkswagen sent about 100 engineers to work together in Isenbottel, a small town about 100 miles north of VW headquarters in Wolfsburg, Germany. A working prototype was unveiled in 2007. Now, Porsche is ready to put it into production.

We recently had the opportunity to test the Porsche hybrid system, and this is what we learned.

How Porsche’s Hybrid System Works

The Porsche-VW hybrid system is unlike any on the market. For the most part, the hybrid is a straightforward parallel system similar to Honda’s Integrated Motor Assist (IMA). However, Honda’s IMA is not a full hybrid because the electric motor can only aid the engine, not propel the vehicle by itself (except in some light cruising conditions). As such, the IMA is considered a “power assist” system.

By comparison, Toyota’s Hybrid Synergy Drive is a power-split full hybrid system that works both in parallel and in series. The power-split device sends most of the engine’s power to the wheels, but also directs some of it to an electric motor that acts as a generator. A second electric motor (and a third in all-wheel-drive applications) aids motive power, and the transmission is a continuously variable automatic instead of a conventional automatic. It is a full hybrid because it can run on engine power, electric power or both.

The Porsche system has basically the same components as Honda’s IMA with one major difference: a disengagement clutch that allows the vehicle to run on gas power, electric power, a combination of both, and no power at all.

It’s easier to understand when you follow the power flow. The Porsche system originates power at the engine, a supercharged, direct-injected 3.0-liter V6 that also powers the Audi S4. Then it flows through the disengagement clutch and a single 38-kilowatt (52 horsepower) electric motor to a new Aisin 8-speed automatic transmission with two overdrive gears that turn the vehicle’s driveshaft and, thus, its wheels.

The clutch is the key component here. It is controlled by a sophisticated Hybrid Manager (basically, a high-power computer) and can disconnect the engine from the drive line (allowing the electric motor to power the vehicle alone) or allow the electric motor to aid the engine when extra oomph! is needed under hard acceleration.

It also gives the system the ability to “coast” or “sail” at highway speeds up to 86 mph. In other words, the Hybrid Manager turns the engine off at highway speeds when it is not needed, such as when traveling downhill. According to Porsche, the start/stop and coasting features allow the Hybrid Manager to turn off the engine 44 percent of the time in the New European Driving Cycle, the equivalent of the EPA’s fuel economy rating cycle. Since the engine can be shut down on the highway, the Porsche system improves highway fuel economy, a plus that not even Toyota can claim.

Porsche quotes total output at 374 horsepower, with the Audi-sourced supercharged V6 producing 333 of those horses. Total torque is 405 lb-ft, and the engine is responsible for 324 lb-ft of torque. The electric motor serves as the alternator and starter, shutting off the engine at stops and restarting it when needed. As in other hybrid systems, regenerative braking recharges the battery. Porsche says the electric motor can also recharge the battery under certain partial-load conditions when the engine is running.

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Can Porsche's new take on hybrid technology change the face of high performance?

Finally, the Porsche hybrid system also integrates a couple of other systems. The steering is electro-hydraulic, instead of just hydraulic, and the air-conditioning system is electrical, linked directly to the battery.

The automaker says the hybrid system increases fuel economy by 25 percent and reduces carbon dioxide emissions by 20 percent, versus a vehicle comparable to the Cayenne and with the same amount of power.