- The Washington Times - Friday, July 24, 2009

The name Porsche evokes images of checkered flags — dreamy-eyed prizes for indomitable victories in 24-hour sports car races — or maybe thoughts of “I’ve made it” status symbols. But rarely is “fuel economy” associated with Porsche.

And such thinking overlooks the fact that Ferdinand Porsche designed the Volkswagen Beetle, and that VW components figured prominently in early Porsche sports car design. So while the original Porsche 356 tuned its VW Beetle-derived engine for extra power, the small, light sports car with VW power was also fuel-efficient.

The ability to combine speed and efficiency is obvious in very lightweight vehicles, such as motorcycles. But as cars have become increasingly burdened with infotainment and climate-control gadgets and armored against impacts with high-strength-steel buttresses and swarms of airbags, there’s only one place to find truly light sports cars that still weigh less than a ton: in the lineups of tiny specialty manufacturers such as Ariel, with its Atom, and Lotus, whose Elise still adheres to the “less is more” philosophy.

Porsche customers today tend to think that less is, in fact, less, and they want all the available techno-widgets they can get. But that doesn’t mean the cars must be thirsty, Porsche reminds us.

The company underscored this point with an opportunity for journalists to spend a day driving its cars from Atlanta, Ga., to Birmingham, Ala., with fuel economy in mind. Our test car was a 911 Carerra 4. In plain English, that means it is the company’s flagship model, the 911, in its all-wheel-drive configuration propelled by a 345-horsepower version of Porsche’s signature flat six-cylinder engine.

This is a good combination for speedy performance, but an amenity-laden curb weight of 3,300 pounds, efficiency-robbing full-time all-wheel-drive, an automatic transmission and abundant horsepower don’t seem like obvious components for thrifty fuel consumption. Temperatures for our fuel-economy run ranged between the low to high 90s over the course of the afternoon, making the air conditioning load substantial.

But Porsche overcomes these potential obstacles with canny application of new technology, including Direct Fuel Injection and a computer-shifted dual-clutch automatic transmission. DFI is the latest and probably final evolution of fuel delivery for internal combustion engines. This design sees the injector squirt the gas directly into the combustion chamber, as happens in diesel engines, rather than further upstream in the intact tract. This provides more precise control of the fuel and also gives the benefit of having the gasoline evaporate while inside the combustion chamber. This evaporation absorbs heat from the chamber, letting engineers up the compression ratio for still better power and efficiency.

Meanwhile, downstream from the engine, new Porsches feature the company’s automatic PDK (Porsche Dopplekupplungsgetriebe) double-clutch transmission. It’s called dual-clutch transmission because there are two clutches instead of one, each serving one of the two transmissions. Both transmissions are in gear, but only one has its clutch engaged. When it is time to change gears, the computer simply opens the clutch that is in use and engages the other one, and the car goes from using the old gear in one transmission to the new gear in the second transmission without any delay or interruption in power flow.

For our test drive, we did nothing remarkable beyond turning the air-conditioning temperature up to 76 degrees to minimize its use on a hot day. Even with it that high, just by turning the A/C off a few miles before reaching our destination, we saw our average fuel economy rise by a few tenths of a mile per gallon, suggesting that driving with no air conditioning would be worth at least a couple mpg over the long run.

Drivers who seek maximum fuel economy are known to do things such as putting their cars in neutral to coast down hills, maybe even with the engine off. These tricks are not only hazardous because of the reduction in control of the car, but they are completely ineffective in a new Porsche, because the Direct Fuel Injection system completely shuts off the flow of fuel to the engine when going downhill with no throttle application by the driver.

After 200 miles of rural two-lane highways, small towns and some interstate highway driving, all traversed at about the posted speed limit (no 25 mph cheater driving), our dark-brown, 345-horsepower, all-wheel-drive missile wheeled into our destination hotel parking lot. The dashboard computer showed the muscular Porsche’s fuel economy over the course of the drive was 30.2 mpg, topping its EPA fuel-economy rating of 18 mpg city and 26 mpg highway.

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