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Previous studies of gasoline direct-injection compression-ignition (GDCI) showed good potential for very high efficiency, low NOx, and low PM over the full speed-load range. Low-temperature combustion was achieved using multiple-late injection (MLI), intake boost, and cooled EGR. Advanced injection and valvetrain were key enablers. In the current study, a new piston was developed and matched with the injection system. Single-cylinder engine tests were conducted with the objective to reduce injection pressure, intake boost, and swirl levels. Results showed that ISFC could be further improved while maintaining low levels of NOx, PM, and combustion noise. Efficiency loss analysis indicated a very efficient thermodynamic process with greatly reduced heat losses. Injection parameters could be used to control combustion phasing with good combustion stability. Engine simulations were performed to develop a practical boost system for GDCI.