Cleaner Than You Think
The promise of excellent fuel economy from diesel engines is one of the great, if largely unreported, factors demonstrated by recent government research. The list of 2002 model-year fuel mileage champs was topped by two hybrid gasoline-electric vehicles, the Honda Insight and the Toyota Prius, followed by three diesel-powered Volkswagen models.
"For yet another year, the release of the 2002 Fuel Economy Ratings by the Department of Energy and Environmental Protection Agency again shows us that diesel-powered cars hold three of the top five government ratings for high fuel efficiency," said Allen Schaeffer, executive director of the Diesel Technology Forum, a government-industry group. "With today's very limited number of diesel choices for consumers, these rankings further underscore the importance of advanced clean diesel power to helping the U.S. meet energy and environmental goals."
The Diesel Technology Forum claims diesels can reduce fuel consumption by 30 to 60 percent in some automotive models, obviously a giant reduction. Further, those kinds of reductions can be accomplished with environmentally clean engines fitted with advanced exhaust emissions controls and after-treatment technology. That point of view was recently reinforced by a study by the National Academy of Sciences.
One example of the diesel future is a special Ford Focus recently unveiled by Ford Motor Company. The new diesel-powered research vehicle is said to meet California's Ultra Low Emission Vehicle II (ULEV II) standards. The vehicle uses co-fueling of diesel and urea, an ammonia-based compound, to reduce nitrogen oxide (NOx) emissions to levels previously not achieved with diesel technology.
While the combustion within a diesel engine might never be as clean as that in an internal combustion engine burning, say, compressed natural gas, catalysts and filters can make the exhaust emissions virtually as pure. The keys to the ULEV II Diesel Focus's low emissions are a very efficient NOx reduction catalyst and a soot-trapping particulate filter. The catalyst uses a water solution of urea sprayed on the catalyst to remove NOx from the exhaust. To ensure that urea is always added to the vehicle, a process called co-fueling is employed. Co-fueling fills the diesel and urea tanks at the same time, so the operation is seamless for the customer.
Along with the NOx catalyst, a particulate filter is used to trap carbon particles. The ULEV II Diesel Focus uses advanced filter technology to provide a diesel vehicle that has no smoke and no odor. The 2007 ULEV II standards for both NOx and particulates, which the Ford Focus will meet, are nearly 90 percent lower than today's standards.
"This prototype vehicle is an example of what could be done to make future diesels fully comparable to gasoline vehicles in emission control, with lower CO2 emissions and excellent fuel economy," said Dick Baker, corporate technical specialist for Ford's Advanced Diesel Systems group.
So one day in the not-too-distant future, our roads might well resemble those in Europe where advanced clean diesel engines already account for about one-third of all vehicles. In some countries, clean diesel cars have over 50 percent of the total market share and upwards of 60 percent of new-car sales. In America the growth potential for diesels is huge, because today diesel passenger cars make up only 0.27 percent of the vehicle fleet. With the big fuel economy advantage and new technology to fix the technology's shortcomings, a new age of the diesel engine may be arriving soon.
Luigi Fraschini, a Cleveland-based auto journalist, has often contributed to Driving Today.