Compare Miller and Atkinson cycles with the standard Otto cycle.

Both Miller and Atkinson cycles improve efficiency by creating an expansion ratio greater than compression ratio. The Atkinson cycle achieves this mechanically with a complex linkage, fully expanding gases to atmospheric pressure. The Miller cycle accomplishes similar results using early or late intake valve closing to create an effective compression ratio lower than geometric ratio, while maintaining full expansion. Toyota Prius uses Atkinson-cycle engines with electric assist to overcome the reduced power density. Miller cycle typically uses supercharging to restore lost power. Both cycles sacrifice power density for efficiency, making them suitable for hybrid vehicles and stationary applications where peak power demand can be met electrically.