Since the LiquidPiston engine...
Since the LiquidPiston engine has one power stroke per revolution, it can make 1 hp per pound. The theoretical efficiency is at 75 percent, while in the form you see here it is 57 percent thermal-efficient. The engines will fall in the 5 to 100hp range.
Just like each brand of truck has strengths and weaknesses, so does each thermodynamic cycle, including the Diesel, Otto, Rankine, and Atkinson (all named after the inventors). The way engineers determine the engines' ability to turn fuel into work is with pressure-volume (P-V) diagrams. As the engine compresses air, ignites fuel, and expands, its pressure and volume are extremely important. The rate and specific type of heat release determines the efficiency of the engine. Knowing this information as well as the amount of fuel delivered, you can determine power. In practice, a diesel operates in a thicker P-V diagram area but, in theory, an Otto cycle has the highest possible theoretical thermal efficiency because of an obtainable spike. Why not combine the best of all cycles into one engine? That is exactly what LiquidPiston did with its engine that uses a high-efficiency hybrid cycle (HEHC). These are the superdiesels I was talking about in last month's editorial.
 The combustion is held under...  The combustion is held under isochoric conditions and the mixture burns for an extended duration of time before the expansion stroke begins. This ensures that fuel and air has a lot of time to mix and burn. The Otto cycle, standard in a gasoline engine, is also modeled as constant-volume. |  During the compression cycle,...  During the compression cycle, this engine operates like a diesel-only compressing air and at pressures greater than 18:1. |  This is the LiquidPiston intake...  This is the LiquidPiston intake cycle, and the yellow circle indicates where we are on the pressure-volume diagram. At this point in the cycle the diagram is only showing volume of air inside the engine. |
 The engineers at LiquidPiston...  The engineers at LiquidPiston basically told us that, during the over-expansion period, the flame is expanded to near-atmospheric pressure, which requires a larger expansion volume than compression volume (as in the Atkinson cycle). A small amount of water may (optionally) be injected during combustion or expansion. This is this engine's power stroke. |  LiquidPiston claims fuel is...  LiquidPiston claims fuel is injected into the combustion chamber and auto-ignites, also similar to the Diesel cycle. However, instead of immediately expanding, the burning fuel and gas mixture is constrained so that combustion occurs under constant volume. |  The exhaust is clean because...  The exhaust is clean because the reaction had time to fully complete. The arrow points to a gate which regulates EGR |