Honda Motor Co. said last week that it will develop a four-cylinder diesel engine within three years that will run as clean as a gasoline engine.
Many automakers are racing to clean up their diesels to meet tightening emission standards. Honda's announcement was a bold statement, given the technological challenges.
CEO Takeo Fukui said Honda will offer two diesel engines in North America, a four-cylinder and a V-6. He said both will meet a U.S. emissions standard known as Tier 2 bin 5. He gave no timetable for the V-6.
The government in 2000 adopted tough new tailpipe emission rules known as Tier 2. The rules - designed to be applied to engines that run on gasoline, diesel or other fuels - are being phased in during the 2004-09 model years. Automakers can engineer for any of eight emission categories, called bins, as long as their fleets meet required averages.
Getting a diesel engine certified to a middle-of-the-pack category, such as bin 5, would be a daunting technological achievement.
Fukui didn't say how the new diesels would meet the standards. Diesels are plagued by high emissions of particulates and oxides of nitrogen.
Honda officials have said they will not follow DaimlerChrysler and other European automakers and use urea. One way to cut diesel emissions is by injecting urea, an organic compound similar to ammonia, into the exhaust.
That leaves two other ways: reducing emissions in the combustion chambers or cleaning up the exhaust with a particulate filter and a trap for oxides of nitrogen.
Automakers prefer reducing emissions in the engine. They are experimenting with high-pressure fuel-injection systems and with lower combustion temperatures achieved by recirculating exhaust gases.
The alternative - adding filters and traps in the exhaust system - hurts engine performance and is expensive.
Diesels are a tempting solution to high fuel costs for drivers and automakers. They deliver about 30 percent better fuel economy than a gasoline engine and are much less complex than hybrids, which use a gasoline engine along with one or more electric motors to power the wheels.
Honda is renowned for its engine expertise. In the mid 1970s, the company introduced the breakthrough CVCC, or controlled vortex combustion chamber, engine.
The CVCC engine enabled Honda to meet 1970 U.S. clean-air standards without using an expensive catalytic converter. Clearly, Honda would like a replay of its CVCC triumph with diesels.
James B. Treece in Tokyo and Harry Stoffer in Washington contributed to this report
You may e-mail Richard Truett at [email protected]