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article imageMaking The Diesel Less Dirty - Particle Filters Seen As The Answer

By Christian Ebner     Sep 8, 2001 in Technology
FRANKFURT - Most motorists agree these days that diesel engines are no longer noisy and sluggish but fears that emissions from compression-ignition motors are more harmful than their petrol- driven counterparts refuse to go away.
Clouds of black smoke are a thing of the past with modern diesel engines yet these still generate microscopic particles of soot which scientists strongly suspect of causing lung damage and even cancer.
Modern filters can neutralize most of these soot emissions but only now have they become so effective that they are being endorsed by the strictest environmental watchdogs.
In Germany the vice-president of the ADAC car club, Werner von Scheven, spoke this week of a "quantum leap" in diesel technology after the particle filter of a stock Peugeot 607 saloon was found to be functioning perfectly after clocking up 80,000 kilometres.
The filter in the 2.2-litre French-made engine had contained and burned up 99.9 per cent of the soot emissions, thanks to exhaust-gas recirculation.
It was enough to earn the praise of Germany's biggest motoring organization and also the country's Environment Ministry (UBA). Both are anxious to see Germany's growing fleet of diesel vehicles kick the soot habit.
"It's not a question of the amount of soot but the concentration of it," said Axel Friedrich who heads the ministry's environment and traffic department. Chemist Ulrich Hoepfner of the Institute for Energy and Environmental Research in Heidelberg believes there is a consensus among scientists that the tiny soot particles could penetrate further into the human body. They may be even more harmful than was previously suspected.
The ADAC will not come out and admit a substantial difference between the filter fitted to the Peugeot by its makers PSA (Peugeot, Citroen) and all the "other suitable technologies" since the big German carmakers have up until now been reticent about particle filter solutions.
Europe's biggest carmaker Volkswagen plans to beat the soot particles by making the combustion of the engine more efficient, so that fewer waste products are exhausted, and by calling for sulphur- free fuel which reduces emissions of harmful hydrocarbons and oxides of nitrogen.
The company also points out that thanks to increasingly strict conditions regarding the composition of exhaust gases, particle emissions from diesel engines have been cut overall by 90 per cent since 1979.
The VW stance notwithstanding, ADAC's von Scheven is convinced that the French filter technology will prevail. The club is soon to gain a powerful ally in the shape of Ford which plans to install filters in its cars.
A spokesman for Ford Germany in Cologne said the latest Fiesta minihatch and the Ka compact will soon be available with a diesel engine fitted with a soot particle filter and developed jointly with Peugeot.
Gerd Lottsipen of the Geman VCD car club, which adopts a more ecological approach, believes the filter battle is entering a decisive phase. The VCD has been campaigning for a long time for all diesels to be equipped with particle filters.
According to the German Environment Ministry, the cost of fitting cars with filter technology works out at about 125 dollars per vehicle.
VW says a figure twice as high is more realistic. Volkswagen also warns that a particle filter makes the frugal diesel use more fuel, something they pointed out when catalytic convertors were first introduced.
The filter is basically a soot particle accumulator but once every 20,000 kilometres the on-board electronic system heats the filter up to 450 degress celsius, destroying the soot deposits inside.
In the case of the Peugeot model a fuel-borne additive called "Eolys" kept in a separate tank causes the soot to burn more easily.
When the car goes in for its 80,000-kilometre service the system is cleaned and the additive refilled. The motor management of a car needs to be programmed to accept the system though, making it hard to retrofit to older vehicles.
However, the French still have problems in reducing the nitrogen oxides in the exhaust of their innovative diesel. Engineers from Volkswagen have boosted the pump injection pressure in their 100- horsepower engine, enabling it to conform with the stringent Euro 4 exhaust standard which does not come into effect until 2005.
Buyers of cars with the Citroen and Peugeot common-rail diesels have to forego the tax break in Germany which is awarded for achieving this ecological benchmark.
The trouble is that agreement on soot particle levels for diesels across Europe is a long way off. International researchers are still trying to devise a universal measuring standard for the minute particles of diesel exhaust which pollute the atmosphere and the introduction of even stricter emission standards for diesels is not in the offing.
More about Mercedes, Diesel, Engines, Peugeot, Vw
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