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A research program designed to measure the contribution from fuel absorption in the thin layer of oil, lubricating the cylinder liner, to the total and speciated HC emissions from a spark ignition engine has been performed. The logic of the experiment design was to test the oil layer mechanism via variations in the oil layer thickness (through the lubricant formulations), solubility of the fuel components in the lubricants, and variations in the crankcase gas phase HC concentration (through crankcase purging). A set of preliminary experiments were carried out to determine the solubility and diffusivity of the fuel components in the individual lubricants. Engine tests showed similar HC emissions among the tested lubricants. No consistent increase was observed with oil viscosity (oil film thickness), contrary to what would be expected if fuel-oil absorption was contributing significantly to engine-out HC. Similarly, no effect of crankcase purging could be observed.

A cold-start partial oxidation (POX) system was integrated with a modern flexible fuel engine to assess its impact on cold-start performance and emissions. The POX reactor, a small combustion device operating fuel rich, converts liquid fuel into gaseous fuel species (reformate). The reformate from the reactor, when mixed with combustion air, replaces or supplements the standard fuel consumed during an engine start. This prototype integrated cold-start system has successfully reduced emissions from a cold-start on fuel grade ethanol (E95) at 5°C. The integrated POX system reduced the time-averaged hydrocarbon (HC) and carbon monoxide (CO) emissions by 80 and 40 percent, respectively. Starts on E95 reformate were achieved in less than 10 seconds at temperatures as low as -20°C.