A novel combustion process has been developed utilizing supercritical gasoline injection-ignition for light-duty compression ignition engines known as Transonic Combustion or TSCi™. Previous publications have demonstrated results for improving fuel economy and emissions under light-load operating conditions typical of those for passenger car vehicles.The TSCi™ combustion process exhibits similarities with HCCI, LTC, PCCI and RCCI with high indicated thermal efficiencies (greater than 45%) and simultaneous reduction of NOx and PM at high EGR levels. The use of EGR at low and medium loads has shown a strong impact on NOx without compromising particulate emissions. However at higher loads with HCCI, LTC, PCCI and RCCI the operating range is limited by excessive pressure rise rates and control of combustion phasing, whereas the TSCi™ combustion process, due to its partially premixed and partially stratified mixture preparation, is not limited in the same manner. For the TSCi™ process the use of copious EGR levels have demonstrated to be effective in reducing NOx and cylinder pressure rise rates while maintaining start of combustion control and low soot emissions at light load conditions.The test results presented in this paper are from extensive single-cylinder engine studies. The results demonstrate the operating range capability of the TSCi™ process at low load without EGR, medium load with use of EGR, and high speed low load with EGR. The results further the technical understanding of the performance of the TSCi™ process into operating regions previously unattained. The impact on thermal efficiency, NOx, PM, hydrocarbons (HC), and carbon monoxide (CO), as well as the ability to control pressure rise rates, combustion stability, combustion duration and ignition delay will be presented. The impact of SOI, Boost, fuel temperature and intake temperature on the supercritical combustion process are also reported.