The invention relates to an improved system of electro-mechanical hydraulic valve lifters for piston engine automobiles that increases fuel economy and reduces fuel emissions. The electro-mechanical hydraulic valve lifters contain that enclose a magnetorheological fluid chamber, containing magnetorheological fluid. A control module manages voltage sent to the magnetorheological fluid in the magnetorheological fluid chamber. The control module introduces various amounts of magnetic flux to the magnetorheological fluid in the magnetorheological fluid chamber. The magnetorheological fluid's viscosity changes based on the amount of magnetic flux applied to it from the electromagnets and, along with the magnetorheological fluid chamber spring, controls how much an intake and exhaust port of the spark plug engine opens to control the amount of fuel used and exhaust let out of the engine.

In one embodiment, a lifter assembly comprises a lifter having a latching mechanism, a slot arranged on an outer wall of the lifter and comprising an inlet that provides access to the latching mechanism, and a pin comprising a fluid channel. The latching mechanism is switchable between a latched position and an unlatched position. The pin is configured to interface with the slot such that the lifter is prevented from rotation about a lifter axis. The fluid channel is configured to be fluidly coupled to the inlet of the slot.

In one embodiment, a lifter assembly comprises a lifter having a latching mechanism, a slot arranged on an outer wall of the lifter and comprising an inlet that provides access to the latching mechanism, and a pin comprising a fluid channel. The latching mechanism is switchable between a latched position and an unlatched position. The pin is configured to interface with the slot such that the lifter is prevented from rotation about a lifter axis. The fluid channel is configured to be fluidly coupled to the inlet of the slot.