|The i-DTEC engine. Click to enlarge.|
At the Frankfurt Motor Show, Honda gave its new advanced 2.2-liter diesel engine a name—the i-DTEC—and put two of them on display. One, the result of “phase one” development, complies with the coming Euro 5 emissions standards. This engine will debut in the new Accord range in Europe in mid-2008.
The second “phase two” engine complies with the US EPA Tier 2 Bin 5 and future Euro 6 emissions standards through the use of a new NOx-reducing catalytic converter. (Earlier post.) With the reduction of engine-out NOx resulting from its combustion system (Premixed Charge Compression Ignition, PCCI), the engine will not require the use of a urea SCR NOx aftertreatment system to meet regulations. This engine is due to debut in the US and Japan in 2009.
For its approach to PCCI, Honda designed a new piston bowl and optimized the nozzle, further cooled the Exhaust Gas Recirculation (EGR), and initiated timing at close to TDC (top dead center). At very light loads, soot and NOx are almost zero. At higher loads, the level of engine out emissions can be lowered drastically, enabling the use of the catalytic converter.
With this catalytic converter, the i-DTEC engine series is capable of exceeding the proposed Euro6 regulation... and we will consider introducing this engine with the catalytic converter in Europe in addition to the US and Japan.—Takeo Fukui, President & CEO, Honda Motor
The new catalytic converter utilizes 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 (N2).
Ammonia is a highly effective reagent for reducing NOx into N2 in an oxygen-rich, lean-burn atmosphere. The system also features enhanced NOx reduction performance at 200–300ºC, the main temperature range of diesel engines.
Alongside developing exhaust gas cleaning technology, Honda is also addressing other technical challenges in developing clean diesel engines, such as handling diesel fuels with different cetane numbers—a particular problem in the US—and meeting US On-Board Diagnostic System requirements.