Pochari Technologies has invented a revolutionary new type of piston engine with hugely improved power density. The engine is a conventional piston engine where a single cylinder serves as two separate combustion chambers. A single piston reciprocates in a two stroke cycle or four cycle providing compression in the opposing chamber each power stroke in opposite chamber for two stroke operation, and every other in four stroke operation. A single cylinder, with the same stroke length as a conventional engine, can provide the equivalent amount of power as two cylinders. By eliminating one set of connecting rods, crankshaft, piston and cylinder we can reduce engine weight significantly. This invention allows for increased volumetric power density, and most importantly, a gravimetric power density increase by almost a factor of 2. This technology will be most attractive for weight sensitive applications, such as aviation. The engine can operate on an Otto cycle, Diesel cycle, or a Pochari cycle (closed cycle hydrogen/oxy combustion. We envision this engine being the most attractive for an Otto cycle, since this engine is most attractive for aviation. The engine will be designed firstly on rich mixture spark ignited hydrogen open cycle operation, for use in Pochari Hydrogen general aviation aircraft. For those interested in licencing, please contact Christophe Pochari at firstname.lastname@example.org.