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InsightCentral.net - Encyclopedia - Honda Insight Advance Catalyst System

The insight is designed to operate at a very lean air fuel ratio during light throttle cruise conditions. The mixture can be as lean as 22:1 if conditions allow. This provides very good fuel economy, and low HC and CO emissions. However, the lean mixture also causes a rise in combustion temperature, and high NOx production is the result.

In order to prevent high NOx tailpipe emissions during lean burn operation, the Insight uses a dual catalyst system that includes an extra NOx storage/NOx reduction catalyst.

The 3-way catalyst is closely coupled to the exhaust manifold to minimize heat-up time, thus reducing emissions after a cold start.

Lean NOx Catalyst Functioning

The lean NOx catalytic converter is comprised of a ceramic A1203 substrate, a platinum (Pt) catalyzing surface, and a titanium-sodium (Ti-Na) NOx storage surface.

During lean burn operation, the exhaust gas contains a larger percentage of oxygen (O2) and NOx, the NOx being primarily nitrogen monoxide (NO). The platinum catalyzes the O2 and NO to produce nitrogen dioxide (NO2), which is able to be stored on the Ti-Na surface.

When it determines that the Ti-Na surface is saturated, the Insight temporarily richens the mixture. This action decreases the NOx and O2 in the exhaust, and raises the levels of hydrocarbons (HC) and carbon monoxide (CO). The platinum is then able to use the HC and CO to catalyze the NO2 (that has been stored) into harmless nitrogen gas (N2), carbon dioxide (CO2) and water vapor (H20).