Method and systems for a multi-fuel engine

A system, comprising:

• an engine having at least one cylinder controlled via an intake valve;
• a first fuel system to deliver liquid fuel to the at least one cylinder;
• a second fuel system to deliver gaseous fuel to the at least one cylinder;
• a variable valve timing actuation system to adjust an opening and/or closing timing of the intake valve;
• and
• a controller configured to:
• responsive to a ratio of gaseous fuel to liquid fuel reaching a first threshold ratio, adjust the variable valve timing actuation system to close the intake valve at a first timing prior to a piston of the at least one cylinder reaching a bottom dead center (BDC) position at an end of an intake stroke, further adjust the variable valve timing actuation system based on engine load;
• responsive to the ratio dropping below the first threshold ratio but still above a second threshold ratio, adjust the variable valve timing actuation system to close the intake valve at a second timing, later than the first timing;
• and
• responsive to the ratio reaching the second threshold ratio, adjust the variable valve timing actuation system to close the intake valve at a third timing, earlier than the second timing and later than the first timing.