Honda to launch clean diesel in U.S. in 09'

10-02-2006, 08:05 PM

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dillsrotary

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Honda to launch clean diesel in U.S. in 09'

http://www.caranddriver.com/carnews/...ree-years.html
"The brilliant thing about Honda’s new clean diesel technology is that it does nothing to alter the character of the company’s existing 2.2-liter i-CTDi engine as found in the European Accord, which is much like our Acura TSX. It is still a torquey little devil, with a baritone growl and pretty strong acceleration after a slightly soft step-off. In Honda’s new clean-diesel application, the engine’s combustion chamber configuration was optimized for a cleaner burn, the injection time was reduced by a new 29,000-psi common-rail system, and the exhaust gas recirculation (EGR) system efficiency was improved.

But the real big deal in this engine is a new dual-layer NOx catalyst (which supplements the existing carbon-monoxide and hydrocarbon-oxidizing catalyst and particulate trap systems) to help meet stringent EPA Tier 2 Bin 5 emissions regulations. This appears to address the diesel engine’s conspicuous failure to match the gasoline engine’s low NOx production. Gasoline engines run at a carefully controlled stoichiometric air-fuel ratio and the exhaust gases are treated by a three-way catalyzation process which reduces NOx by about 99 percent.

This is impossible in the oxygen-rich environment of a lean-burn diesel engine, where three-way catalysts achieve perhaps a 10-percent reduction in NOx. In response, some manufacturers have been employing urea-injection systems to reduce NOx emissions. But not Honda.

Instead, the company’s new dual-layer catalyst operates in three stages: During lean-burn operation, the lower layer adsorbs NOx from the exhaust stream. Then, when necessary, the engine management system switches to a richer air-fuel ratio, allowing hydrogen (H2) obtained from the exhaust stream to react with the adsorbed NOx to produce ammonia (NH3). An adsorbent upper layer then temporarily adsorbs the ammonia. As the engine resumes lean-burn operation, the adsorbed ammonia in the upper layer reacts with NOx in the exhaust stream, reducing it to nitrogen.

The effect is similar to having an onboard ammonia source (such as Mercedes-Benz’s AdBlue urea supply), but without having to replenish the tank. Honda showed a real-time exhaust-gas trace from conventional and dual-layer-catalyst–equipped cars running the same cycle, and the new engine’s emissions adhered closely to the EPA-mandated level. Only when accelerated hard did the new system spike above that level, but to a much smaller degree than did the conventional diesel.

Honda is naturally circumspect in regard to the exact material specification of the new catalyst, but it’s clear that engine management plays a large role in the control of the new catalyst’s functions. So even when competing car manufacturers reverse-engineer Honda’s components, as they undoubtedly will, they will probably still face significant engineering challenges."

Last edited by dillsrotary; 10-02-2006 at 08:08 PM.

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