BIRMINGHAM, AL – Tweaking an engine to produce more horsepower is simple stuff; engineering a vehicle with stellar chassis dynamics and just the right amount of power to deliver both great fuel economy and uncompromised performance is more difficult.

This is the holistic new philosophy of Porsche AG, an auto maker steeped in motorsports history but suddenly having to comply with the U.S. mandate to achieve fleet fuel economy of 35.5 mpg (6.6 L/100 km) by 2016.

“Our engineers are holding back on power – they are looking elsewhere now” for optimum performance, says Alexander Schildt, manager-product planning for Porsche Cars North America.

“We want our customers to be able to pull up in front of their children’s schools and not feel like they are causing climate change all by themselves,” Schildt tells Ward’s during a media preview for the Panamera with its all-new 3.6L V-6, as well as the new-for-’11 Porsche Cayenne.

The Panamera’s new DOHC V-6 mirrors the design and technology of Porsche’s well-regarded 4.8L V-8, minus two cylinders. The engine is the first Porsche-designed V-6 in a production car.

But it makes only 300 hp, a threshold surpassed years ago by mainstream auto makers selling vehicles for a fraction of the cost. Panamera V-6 pricing starts at $74,400, excluding destination charges.

Schildt says industry watchers often place too much emphasis on horsepower and torque ratings but fail to recognize the importance of integrating that thrust into the vehicle.

For instance, Porsche’s 4.8L twin-turbo V-8 produces 500 hp and 516 lb.-ft. (700 Nm) of torque in the ’11 Cayenne cross/utility vehicle.

He says tuning the engine for 600 hp would be easy and invite comparison with AMG, the high-powered performance division of rival Mercedes-Benz.

“That’s not something we want to do, to be in a horsepower war,” Schildt says. “Those horses are hungry and want to be fed.”

In the motorsports world, Porsche has proven out its “Intelligent Performance” theory by often running engines with lower horsepower than its competitors, yet still prevailing at the checkered flag.

The lynchpin in the strategy is to maintain a laser focus on reducing mass from bumper to bumper. “Take weight out of a car and it does magic for the handling,” he says. “That’s how we will continue to satisfy our customers.”

The new water-cooled DOHC 90-degree V-6 has direct injection, four valves per cylinder, a compression ratio of 12.5:1 and standard VarioCam Plus valve timing.

With 300 hp and 295 lb.-ft. of torque, the Panamera’s all-aluminum V-6, coupled with the PDK dual-clutch transmission, sprints to 60 mph (96 km/h) in a respectable 6 seconds. With the Sport Chrono Package Plus, the run can be done in 5.8 seconds. Add all-wheel-drive, and the time drops further to 5.6 seconds.

Meanwhile, the Panamera is rated at 18/27 mpg (13-8.7 L/100 km) in city/highway driving. With AWD, the highway mileage drops to 26 mpg (9 L/100 km).

The new emphasis on fuel economy in the U.S. has placed Porsche at a crossroads, and Schildt says he is certain the proper path takes the brand further into hybrids, such as the all-new Cayenne, which arrives later this year. A hybrid Panamera also is in the pipeline.

“If we want to stay in business, we must do this,” Schildt says of improving fuel economy across the Porsche lineup. “You cannot buy your way out of it.” Historically, Porsche has paid between $3 million and $4 million annually in non-compliance penalties.

Porsche powertrain engineers needed some time to get on the fuel-economy bandwagon, but Schildt says he is certain they are onboard with the mission.

“Yes, they are performance-minded,” he says of the powertrain team. “But they also like a good challenge. The way to solve this problem is with good ideas and great engineering. We think customers will pay for that.”

At this year’s Geneva auto show, Porsche displayed the hybrid Cayenne and two additional hybrid concepts, the 2-seat 918 Spyder and 911 GT3 R, the auto maker’s first hybrid racing car.

“These three cars, together, show we do believe in the future of sports cars, even in a world where CO2 emissions take the lead over performance numbers,” Schildt says.

tmurphy@wardsauto.com