We report a proprietary closed liquid magnetohydrodynamic cycle, the simplest application of Lorentz’s law to a moving conductor with crossed electrodes and a magnetic field with no moving parts, having a potential of MHD power conversion efficiency that approaches the loading factor W (ratio of the electric field across the load to the open circuit electric field). Since the MHD efficiency may approach W = 1, the electrical conversion of the power of the plasma into electricity may approach the efficiency of pressure-thermal to kinetic energy conversion wherein the corresponding nozzle efficiencies of 99% have been realized. Calculations were carried out for a flow rate of 1 kg/s, a gas conductivity 106 S/m, a uniform magnetic field of 2 T, and inlet pressure, temperature, and velocity equal to 1 atm, 1000 K and 1000 m/s, respectively. These parameters result in the extraction of 471 kW of MHD power from a 16 cm long channel with 4 cm2 maximum cross section and gas exit temperature of 1800 K wherein the heat inventory is recovered by gas absorption in molten silver. The silver is recycled with insignificant power using electromagnetic pumps having no moving parts. The channel volume is 20.4 cm3 so the corresponding MHD power density is about 23.1 kW/cm3 (23.1 MW/liter) which compares very favorably with typical power densities in the range of only about 30 kW/liter for state-of-the-art high-speed heavy-duty diesel engines.