Honda diesels clean up

Honda's next generation of diesel engines will meet upcoming emissions standards anywhere in the world, for years to come.

And they will do so using a common chemical usually associated with breaking up mud and greased tracked in on a house-proud home-owner's kitchen floor.

Diesels are traditionally worse polluters than petrol engines, when measuring particulates and nitrous-oxides (NOx). That's why the Americans are pursuing hybrids, and particularly plug-in hybrids for the US market, which is following California's draconian emissions legislation lead.

California's legislation has been the 'catalyst' for new US federal legislation titled 'Tier II/Bin 5', said to be more restrictive than the proposed parameters of the European Union's 'Euro 6' emissions standard.

Tier II/Bin 5 will apply fully from 2009 and is equivalent to California's LEV II standard. The two standards will force manufacturers' light vehicle fleets to achieve a level of NOx emissions as low as 43.5 mg/km.

Honda's 'super-clean' engine was introduced at Frankfurt and it's this engine that will meet the proposed American standard as well as the proposed standards in Europe and Japan.

The 'Super-clean' engine is fitted with a lean-burn catalytic converter that creates a chemical reaction between ammonia and nitrous-oxide (NOx) to convert the toxic chemical to nitrogen, which is inert and constitutes 80 per cent of our atmosphere.

Similar results have been achieved using urea to convert the NOx, but the beauty of Honda's system is that the ammonia is created within the car's exhaust system, by selectively removing NOx from the exhaust gas in one layer of the 'cat' and mixing it with hydrogen scavenged during rich running to produce ammonia. The ammonia is stored in a second layer of the catalytic converter and then mixes with the NOx to convert to Nitrogen.

Honda claims to have achieved better results with this method in the 200-300-degree Celsius engine exhaust temperature range.

Conventional diesel engines equipped with three-way catalytic converters only succeed in reducing NOx by approximately 10 per cent, compared with petrol engines that can reduce NOx by as much as 99 per cent. The 'Super-clean' Honda engine can achieve petrol engine levels of NOx reduction.

Being a relatively compact system, the additional catalytic converter doesn't impinge unnecessarily on vehicle design and packaging either.

In the more immediate future, the first i-DTEC engine (pictured) -- an upgrade of Honda's existing diesel engine family and apparently an abbreviation of 'Intelligent Diesel TEChnology' -- will make an appearance in next year's Honda Accord, the car that has been revealed in its 'Tourer' concept (more here).

Displacing 2.2 litres, the new diesel is more powerful (developing 102kW) and more economical, as well as being cleaner.

This engine will comply with Euro 5 emissions levels, which calls for diesel particulates to be reduced 80 per cent from the levels permitted under Euro 4 and nitrous-oxides are to be cut from 250 to 180 mg/km.

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