In two-stroke S.I. engines, direct fuel injection prevents fuel loss from the exhaust port, since only air is employed for the scavenging process. However, to solve the problem of combustion irregularity at light loads due to excessive presence of residual gas in the charge, fuel injection should also produce charge stratification. An alternative to stratification is ATAC (Active Thermo Atmosphere Combustion), which turns the effect of residual gas from negative to positive, since residual gas energy is exploited to prime the combustion of fresh gas. For the first time, the feasibility of ATAC combined with liquid high-pressure direct injection is proved in this paper. To illustrate the compatibility of ATAC with fuel injection, ATAC behaviours are shown in the cases of liquid high-pressure direct injection, air-assisted medium-pressure direct injection and indirect injection.