The influence of the number and the size of the fuel-injector orifices and their opening pressure on the performance and emissions of an uncooled, thermally insulated diesel engine was experimentally investigated. Increasing the number of orifices was generally found to decrease the Brake Specific Fuel Consumption (BSFC) and smoke emissions but to increase the nitric-oxide (NO) emissions. Increasing the number of orifices resulted in a slight increase in premixed burning and in a substantial decrease in the duration of combustion. Increasing the orifice size increased the BSFC and smoke emissions but decreased the NO emissions. The heat-release characteristics were not significantly altered, however. Finally, increasing the opening pressure of the injector increased the BSFC and smoke emissions and decreased the NO emissions of the uncooled engine.