Direct injection through a twining injection system enables an increase in output power of dual-fuel engines, improves the speed control capacity, and allows the engine to use flexible gaseous fuel blends of syngas-biogas-hydrogen with large variation of compositions. The stop injection angle is determined by the maximum power and rated speed of the engine. The air to fuel equivalence ratio is adjusted by the start injection angle. When the injection pressure is reduced from 5 bar to 3 bar, the start injection angle is advanced by 20TK and the gauge pressure in the cylinder drops by 0,1 bar. In syngas fueling mode, with an injection pressure of 3.5 bar, to achieve =0.75 at a crankshaft position of 250TK, the start injection angles are 80TK, 50TK, and 25TK corresponding to engine speeds of 2000 rpm, 2400 rpm, and 2800 rpm, respectively. The gauge pressure in the cylinder is 0.77 bar, 0.85 bar and 0.89 bar, respectively, correspondingly increasing by 100%, 97%, and 79%, compared to natural aspiration fueling mode.