New diesel cars forging ecology path

TOKYO -- Japan, Europe and the United States plan to implement by 2010 drastically toughened restrictions on automobile emissions, with vehicles that fail to clear the standards banned from sale.

European carmakers are set to launch more models in Japan using advanced engines, which are less polluting, while some domestic automakers, including Toyota Motor Corp., will introduce more hybrid cars.

Developments in environmentally sound technologies are becoming more and more important for automakers competing in the world market.

On Aug. 28, DaimlerChrysler Japan Co. released a diesel-powered Mercedes-Benz E-class model.

Though having the same appearance as gasoline-powered E-class models, they have advanced diesel-powered engines, which significantly reduce emissions of both nitrogen oxide (NOx) and particulate matter (PM).

Similar diesel-powered Mercedes-Benz models, using what is known as the common rail diesel engine, have been sold in Europe since 1997 and pass Japan's current car emission regulations.

The sale of these diesel-powered models in Japan has been slow going until recently due to negative impressions consumers have about diesel-powered cars.

A major difference between gasoline-powered engines and those fueled by diesel is that diesel contains more sulfur, which means diesel engines emit more PM when fuel is burned incompletely at low temperatures, and they discharge large amounts of NOx when the fuel is burned completely at high temperatures.

A great challenge presented to makers of diesel-powered cars has been to develop technologies to reduce emissions both of NOx and PM, which has led to the common rail engine design.

The common rail diesel engine stores fuel in a central chamber called a rail at high pressure and then injects the fuel into the engine's pistons at levels that depend on the car's running condition.

With electronic devices to precisely control the frequency and quantity of fuel being injected to keep the balance between high- and low-temperature combustion, the common rail engine has succeeded in reducing emissions of both NOx and PM.

NOx and PM are typical of harmful substances contained in car exhaust. NOx is the cause of photochemical smog and acid rain. PM, or black soot, causes respiratory problems.

Since 1992, Japan has strengthened regulations on such emissions by gradually revising the safety standards under the Road Trucking Vehicle Law.

The current regulation is a long-term one implemented in 2005 that imposes different maximum allowable quantities on each of the harmful substances for gasoline- and diesel-powered cars.

The most strict standard is for diesel-powered vehicles weighing 3.5 tons or more, with the maximum allowable quantity being 2 grams of NOx and 0.027 gram of PM per kilowatt-hour of engine output.

In 2009, a stricter regulation to replace the 2005 one will be implemented, with the maximum allowable emissions to be cut by two-thirds of today's standards.

The United States plans to drastically cut NOx emissions under regulations to be applied in and after 2010.

Euro5, a new regulation to be implemented in 2008 in the European Union, will likely be less strict than those in Japan and the United States concerning NOx and PM emissions. But Europe has strict regulations on the greenhouse gas carbon dioxide.

The common rail diesel engine emits 20 percent to 30 percent less CO2 than its gasoline-powered counterparts, meaning nearly half of all passenger cars in Europe are run on diesel. Thirty percent to 40 percent of passenger cars sold by Japanese makers in Europe are diesel-powered.

Japan's current maximum allowable quantity of NOx in car emissions is, in the case of passenger cars, 0.05 g/kWh. In the 2009 new regulation, the maximum figure for PMs will be newly imposed on some models. The limit will be 0.005 g/kWh for passenger cars.

Gas-powered engines usually discharge relatively little PM, and catalysts in the engine can dissolve NOx.

In addition, hybrid cars by Toyota and other Japanese makers emit less CO2 than normal gas engines by combining gas-powered engines with electric motors.

Many in the automobile industry see hybrid cars as a promising global strategic product for the future.

A Toyota official said the company's Prius hybrid models emit negligible quantities of PM and 0.013 gram or less of NOx per kilometer.

The Prius models likely will be able to clear emission regulations in Japan, the United States and Europe even after standards are tightened, the official said.

It is a task for Toyota and other makers of hybrid cars to further improve environment-related performances of hybrid engines for larger-sized passenger vehicles.