The Square Piston Engine (SPEC), a two-stroke engine with a square piston, has an improved power-to-weight ratio compared to existing engines. The engine features the same three moving parts as a conventional two-stroke engine: crank, gudgeon, and piston. The delayed opening of the exhaust port on the power stroke provides a cleaner burn of the fuel, yielding more torque and lower emissions. The SPEC also has a closed-loop engine oiling system, which provides component durability and reduced hydrocarbon consumption. The engine is modular in design, providing significant manufacturing flexibility.A number of prototypes have been constructed and have operated on a variety of fuels. One such prototype has run in excess of 500 hours. Further development work is required to enhance engine efficiency through software modeling of port placement.