PSI Designs, Engineers & Manufactures Emission-Certified, Alternatively-Fueled Engines & Power Systems Power Solutions International, Inc. (PSIX) provides integrated turn-key engine and power solutions to leading global original equipment manufacturers in the industrial, off- and on-road markets. Our unique in-house design, prototyping, engineering and testing capacities mean we can customize clean, high-performance engines that run on a wide variety of fuels including natural gas, propane, biogas, gasoline, or hybrid systems to meet and exceed applicable environmental standards.