Low-pressure dual fuel (LPDF)

A low-pressure dual-fuel engine admits gas at a few bar into the cylinder or port and ignites the lean premixed charge with a small pilot of liquid fuel, running an Otto (lean-burn) cycle in gas mode and a diesel cycle on liquid backup. Wartsila 31DF and 50DF and the WinGD X-DF two-strokes are examples. The trade is much lower fuel-gas supply pressure than high-pressure (Diesel-cycle) injection, against a risk of methane slip and knock at high load.