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Extensive simulation was carried out to investigate cam strategies for SI engine part load operation. Performance of the engine with dual independent variable cam timing (VCT) system is assessed. Over a wide range of part load operating conditions, engine performance parameters, such as fuel consumption, were expressed in forms of contour maps as a function of intake and exhaust cam timings. Based upon the simulation results, cam timings were optimized for various part load conditions. A cam strategy incorporating intake and exhaust cam retard was developed to improve fuel economy and emissions. Influences of intake and exhaust cam timing on the gas-exchange and combustion processes were also analyzed. It was shown that the fuel economy improvement by dual independent VCT is achieved primarily through reduction of pumping loss. Effects of in-cylinder charge motion and the use of differential intake cam profiles on fuel economy were examined.