The technology, if made production-ready, would give automakers another fuel-efficient powertrain option for the U.S. market. Strict limits on particulates and oxides of nitrogen, or NOx, set by California for 2007 are cited by automakers as one of the primary obstacles to using diesels in cars and light trucks.
Diesels can improve fuel economy by up to 30 percent compared with gasoline engines. They also offer a quicker and less expensive alternative to gasoline-electric hybrids.
Ford claims a diesel-powered Focus sedan that uses a urea injection system gets 59 mpg on the highway, virtually the same as the upcoming hybrid version of the Honda Civic sedan. Ford engineers say the Focus sedan with a turbocharged diesel engine and urea injection system likely will meet the toughest emissions regulations on the books, California's Ultra Low Emissions Vehicle II standards scheduled for 2007.
The diesel Focus' performance is nearly equal to a gasoline-powered Focus and would cost only a few hundred dollars more, said Dick Baker, technical specialist for Ford's Advanced Diesel Systems Group.
But the lack of a distribution infrastructure is a major roadblock for urea, an ammonia and water solution. A supply of urea must be kept onboard the vehicle in a separate tank. The vehicle will continue to run if the urea tank is empty, but it won't comply with emissions regulations.
How it worksUrea is injected into the exhaust system before the exhaust enters the catalytic converter. Along with the catalyst, a particulate filter is used to trap soot. The urea converts NOx and hydrocarbons into nitrogen and water, eliminating nearly all the nitric oxide.
The California Air Resources Board has enacted strict NOx reduction regulations based on the belief that NOx causes cancer.
Only about one-half gallon of urea is needed per 14-gallon tank of diesel, at a cost of about $1.50.
Ford test results show that the system easily meets most ULEV II standards in short mileage tests. Baker says Ford still has to find out whether urea injection can hold down emissions after high mileage tests.
Engineers and automakers are enthusiastic about urea's ability to bring down emissions but are skeptical about solving the fueling issue.
"As of right now, we are looking at it, of course, but I don't see it as the way we are going to go," said Jack Blanchard, GM's assistant chief engineer for diesel engineering. "If we could get it done (fix the infrastructure) as an industry, we'd probably move on it."
Prototype fuel nozzleFord has developed a prototype nozzle that fills the urea tank and the diesel tank at the same time. Drivers would not have to do anything different when they refuel because the nozzle automatically shuts off the flow of urea once the urea tank is full and lets the diesel fuel continue to flow until the tank is full.
Ford's Baker says the prototype nozzle could work with an additive pump sold by Additech Inc. of Brookfield, Conn. Additech sells electronic dispensers to service station owners that allow drivers to put additives such as fuel system cleaners in their tank at the same time they fill up.
Rod Carnes, vice president of marketing for Additech, says there are no barriers to installing the technology and estimates it might cost between $3,000 and $6,000 to outfit each diesel pump with a urea fueling system. The cost, he says, likely would be borne by the distributor of the urea or the filling station owner.