LiquidPiston’s HEHC is a patented thermodynamic cycle that combines the advantages of Diesel, Otto and Atkinson thermodynamic cycles. The cycle elements include:
- Compression: For maximum efficiency, air is compressed to a high compression ratio, fuel is injected and compression ignited (CI-HEHC). The X Mini utilizes a spark-ignition (SI-HEHC) version of the cycle with a lower compression ratio standard for gasoline engines.
- A dwell near top-dead-center forces combustion to occur at nearly constant-volume conditions.
- Combustion products are over-expanded using a larger expansion volume than compression volume, as in the Atkinson Cycle.
- Cycle-skipping power modulation allows high efficiencies at low power settings while simultaneously cooling the engine’s walls internally and providing partial heat recovery.
- Water may be injected to internally cool the engine. Some of this cooling energy is recuperated, as the water turns to steam, increasing the chamber pressure.