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Diesels look to rev up their reputations

High-performance diesels will soon exploit the fuel economy benefits of diesel power while delivering the neck-snapping acceleration associated with gas guzzlers. By Dan Carney.
The diesel-powered Mitsubishi Concept-RA sport coupe is no soot-belching school bus.
The diesel-powered Mitsubishi Concept-RA sport coupe is no soot-belching school bus.Mitsubishi / Mitsubishi

Diesel-powered vehicles haven’t enjoyed the best reputation in the United States, despite the well-known benefit of impressive fuel efficiency. Consumers have long been unimpressed by other traits, such as their black clouds of exhaust soot, ear-rattling racket and, ahem, let’s call it “stately” acceleration.

But an emerging generation of new diesel vehicles looks set to upend those expectations. Some high-performance models will soon exploit the fuel economy benefits of diesel power while delivering the neck-snapping acceleration associated with gas-guzzling cars.

Consider the Audi R8 TDI Le Mans, a 500-horsepower V-12 midengined supercar that can reach 186 miles per hour and rockets from a standstill to 60 mph in a shade over four seconds — no soot-belching school bus, this.

“Diesel, in many ways, is the future of performance technology,” said David McConnell, chief designer for Mitsubishi R&D America, the automaker that created the diesel-powered Concept-RA sport coupe, which made its world debut at this year’s Detroit auto show.

Current U.S. emissions regulations demand that diesels must be as clean as gas-powered cars. The result is that there are few diesels currently offered for sale, but a comparative diesel flood will arrive in 2009 as carmakers seek to boost their fleets’ fuel economy to meet tougher new fuel-economy requirements, known as corporate average fuel economy (CAFE) standards.

And while that 10-year-old Dodge Ram pickup with the Cummins turbodiesel and 18-wheeler-wannabe exhaust stacks sitting next to you at the traffic light still forces you to close your window and curse its oppressive noise, today’s diesels are so quiet it’s hard to distinguish them from gas-powered models, and that’s why you probably haven’t noticed them on the road.

But that obnoxiously loud Ram does serve as an indication of things to come in terms of power and performance. Ram drivers embraced those diesel engines and fitted their trucks with hot-rod parts because diesels not only sip fuel, they can also churn out prodigious power.

And now carmakers are harnessing that power for use in sports cars such as the Audi R8. Audi even competes at the prestigious 24-hour sports car race at Le Mans with diesel-powered racecars. They have won that race and others, beating gasoline-fueled racers in the process.

Mitsubishi’s Concept-RA features the company’s all-wheel-drive for its sport coupes, but adds efficient diesel power to ensure such a car will still be relevant if it reaches production in the future.

The Concept-RA’s 201 horsepower is plenty to deliver a sporty driving experience, but by using a diesel instead of a gas engine the car’s owner can enjoy more tolerable fuel economy. Rather than try do disguise this fact, the Concept-RA’s designers highlight the diesel engine by leaving it exposed to view through an opening in the hood.

“The reason we showed that is that diesel power is the prime story around this car,” McConnell explained.

Companies like Ferrari and Bentley have announced plans to reduce the carbon dioxide emissions of future models, but they are expected to stick with gasoline engines, probably using E85 fuel. Both companies say that their customers expect the experience delivered by a gas engine. “Our customers expect a different sound,” than they would get from a diesel, explained Ferrari spokesman Davide Kluzer.

But BMW and Mercedes are embracing diesel power, even for sporty models. BMW has dubbed its effort “EfficientDynamics,” and the company’s diesel lineup includes a 204-horsepower version of the new 1-series compact model. Producing more than 200 horsepower from 2.0-liters of displacement means the engine exceeds the 100 horsepower per liter threshold long seen as the line of demarcation between “regular” engines and true high-performance power plants.

Unlike those automakers building limited production economy or performance models, BMW offers this technology across its product range, explained Norbert Reithofer, chairman of the board of management.

“All models offer higher dynamics at lower fuel consumption,” he said. “EfficientDynamics is not only installed on one or two ecological models. On the contrary, EfficientDynamics operates across the entire model range.”

Audi will offer its Q7 crossover SUV with the monstrous 500-horsepower V-12 diesel in the R8 sports car shown at this year’s Detroit and Geneva auto shows, giving that vehicle improved power and fuel economy compared to today’s gas models. In Geneva, Mercedes showed a concept version of its GLK compact crossover vehicle with a twin-turbocharged diesel backed with an electric motor that together produce 224 horsepower.

The option of diesel power presents the possibility of even traditional American iron like the Chrysler 300 nursing its drink rather than gulping it down. Because the 300 uses the same V6 engine that Chrysler plans to offer in the Grand Cherokee, we know the company is gearing up to use the engine here. The company may opt to sell the diesel version of the 300 that it offers in Europe to U.S. consumers.

General Motors is bullish on diesel’s potential to reduce the consumption of pickups and SUVs, but CEO Rick Wagoner is more guarded about its potential in cars.

“You are going to see an explosion of diesels in the truck segment,” he predicted. “Don’t rule out cars, but we aren’t forecasting a huge increase in the U.S. market demand for diesels.”

Still, the National Academy of Science hopes there will be such an increase, because of the fuel-saving potential.

“The light-duty diesel vehicles in production and in widespread use in Europe have already demonstrated a 30-40 percent reduction in fuel consumption, depending on engine size, compared with 2007 model-year gasoline engines,” said the academy in a report to the government last month on fuel economy standards.

If government regulators remain skeptical about diesel’s potential, maybe they should arrange to take an Audi R8 TDI LeMans for a test drive at the race track.