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Experimental investigations were conducted on a multi-cylinder automotive scale HCCI engine in determining a strategy that yields high power output, sufficient for passenger vehicles. A 1.9L Volkswagen TDI, modified for HCCI operation, is used with a compression ratio of 17:1 and boost pressures between 1.0 and 2.0 bar absolute. Various equivalence ratios and combustion times are explored at 1800 RPM with commercial-grade gasoline. The effects of exhaust backpressure that would be caused by a turbocharger in production engines are also explored. The results reveal that the highest power output can be achieved with high boost pressures and high equivalence ratios, and highly delayed combustion timing for controlling ringing. The optimal power output conditions exist near the boundaries of ringing, peak in-cylinder pressure, misfire and controllability.

Steady-state, transient and dithering characteristics of emission conversion efficiencies of three-way catalysts on natural gas IC engine were investigated experimentally on a single-cylinder CFR engine test bench. Steady-state runs were conducted as references for specific engine emission levels and corresponding catalyst capacities. The steady-state data showed that conversion of HC will be the major problem since conversion of HC was effective only for a very narrow range of exhaust mixture. Unsteady exploration runs with both lean-to-rich and rich-to-lean transitions were conducted. These results were interpreted with a time scale analysis, according to which a qualitative oxygen storage model was proposed featuring the difference between oxygen absorption and desorption rates on the palladium catalysts.