In its ongoing quest to perfect the rear-engined 911 Carrera, Porsche AG will introduce new technologies aimed at improving both the performance and efficiency of the classic sports car.

When they reach U.S. dealers in September, the new ’09 Carrera and Carrera S models will feature for the first time direct-gasoline injection (DGI) on their respective 3.6L and 3.8L DOHC flat-6 boxer engines, as well as an optional 7-speed dual-clutch transmission (DCT).

Porsche says the new drivetrains improve fuel efficiency of the 911 up to 13% in the European driving cycle, while also significantly boosting acceleration.

Carrera and Carrera Cabriolet models with the base 3.6L engine gain 20 hp from the addition of DGI for a total of 345. Coupe and convertible S variants gain even more punch, with the 3.8L boxer up 30 hp to 385 and capable of propelling the Carrera S to 188 mph (303 km/h).

The new 7-speed PDK (Porsche-Doppelkupplung) transmission is similar to other DCT units on the market and will replace the current 5-speed Tiptronic S gearbox. A 6-speed manual will continue to be offered as standard.

Porsche developed its dual-clutch principle more than 25 years ago for racing applications, the auto maker says, and plans to introduce the technology throughout most of its lineup.

While the PDK gearbox features an automatic mode for smooth, everyday cruising, the seamless power delivery through the twin clutches allows for gear changes faster than any human can manage with a conventional manual.

The auto maker says Carrera and Carrera S coupes equipped with the PDK can sprint to 60 mph (97 km/h) in 4.5 and 4.3 seconds, respectively, about 0.2 seconds faster than with the standard transmission.

An additional 0.2 seconds can be shaved from those times with the optional Sport Chrono Plus option, which features a launch-control function, as well as a dash-mounted lap counter and stopwatch.

Distinguishing the new cars is a new front fascia with larger air intakes, along with revised exterior mirrors and light-emitting-diode daytime running lights, taillights and brake lights.

New alloy-wheel designs also are available, as are Dynamic Cornering Lights for the standard bi-xenon headlights.

Much of the interior is unchanged, with updates focused primarily on electronics content.

Porsche’s PCM 3.0 communications system is standard on all models and now is operated via a touchscreen interface.

Additional infotainment options include a hard-disk drive navigation system, XM radio and NavTraffic service, Bluetooth connectivity and auxiliary jacks for personal electronics, such as iPods.

Fuel-economy figures and destination charges will be finalized closer to launch, but the auto maker says the ’09 911 lineup will base from $75,600 (Carrera coupe) to $96,800 (Carrera S Cabriolet), with both the Carrera Cabriolet and Carrera S coupe starting at $86,200.

msutton@wardsauto.com