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For a long time, the Europeans had a head start compared to the Japanese in the field of automotive technology. Of course, by now, the way the Japanese leapfrogged the technology learning curve to play catch up with the Europeans is part of history lessons that we Indians want to read and emulate.

The case with diesel engine technology is similar, with the Europeans recognising the potential of diesel and investing in this technology early. And the Japanese, the big car manufacturing hub in the East, being rather slow to spot the potential in diesel.

Of the Japanese manufacturers, Honda was a late starter in the field of diesel automotive engines for application in passenger cars.

But, despite its delayed entry, Honda has leapfrogged the technology progression that European manufacturers have had to go through in the fields of diesel fuel injection and exhaust treatment. Honda made a break into the big league with an extremely environment-friendly new diesel engine technology called i-CTDi that was first unveiled at the Geneva Motor Show of 2003.

The 2.2-litre diesel engine featuring this technology is currently offered in the European Spec Accord and CR-V.

The focus with diesel engine technologies continues to be on performance and refinement that benchmarks them with similar sized gasoline engines, however, there is now also a very sharp focus on emissions.

As result, even though the Honda i-CTDi lean-burn, low-emission engine meets Euro 4 norms, it is not good enough to meet the US’ stringent emission norms, where diesel has a good chance making inroads, if the engines can meet the more rigorous Tier II Bin5 emission norm for diesel passenger cars.

The most polluting and difficult to control emission from diesel engines continues to be nitrogen oxides. The US’ emission norm can be met by diesel engines that use special post-treatment catalytic converters where pre-installed equipment injects liquid ammonia or urea into the exhaust chamber. This leads to the conversion of nitrogen oxides (NOx) into harmless nitrogen.

However, this system, which is currently in use in Honda’s own i-CTDi engine and Mercedes Benz’s BLUETEC engines, has a limitation as far as the US market regulator EPA (Environment Protection Agency) is concerned. The ammonia tank needs to be replenished at regular intervals and the emission technology’s performance hinges on the tank having adequate liquid ammonia.

With Honda’s new i-DTEC engine and the self-generating catalytic converter, the company has managed to do away with the requirement for an ammonia tank. In addition to the refinements made to the i-CTDi engine’s combustion chamber configuration and fuel injection system that sports a 2000-bar common rail injection system, the primary changes in the new i-DTEC engine revolves around a new catalytic converter system.

The new i-DTEC engine’s catalytic converter utilises a two-layer structure - one layer adsorbs NOx from the exhaust gas and converts a portion of it into ammonia, while the other layer adsorbs the resulting ammonia, and uses it later in a reaction that converts the remaining NOx in the exhaust into nitrogen.

This ability to generate and store ammonia within the catalytic converter has enabled Honda to create a compact, lightweight NOx reduction system for diesel engines. Further, the car user need not refill an ammonia tank during regular intervals, failing which the emissions target will not be met.

The new i-DTEC engine is likely to be launched by Honda in its 2009 models for the US market.

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