page_title: Atkinson cycle
section_title: Ideal thermodynamic cycle
hierarchical_section_title: Atkinson cycle / Ideal thermodynamic cycle
caption_attribution_description: Atkinson or Miler cycle in p-V diagram.
context_page_description: The Atkinson-cycle engine is a type of internal combustion engine invented by James Atkinson in 1882. The Atkinson cycle is designed to provide efficiency at the expense of power density.
  A modern variation of this approach is used in some modern automobile engines. While originally seen exclusively in hybrid electric applications such as the earlier-generation Toyota Prius, later hybrids and some non-hybrid vehicles now feature engines with variable valve timing, which can run in the Atkinson cycle as a part-time operating regimen, giving good economy while running in Atkinson cycle, and conventional power density when running as a conventional, Otto cycle engine.
context_section_description: The ideal Atkinson cycle consists of:
  1–2 Isentropic, or reversible, adiabatic compression
  2–3 Isochoric heating (Qp)
  3–4 Isobaric heating (Qp')
  4–5 Isentropic expansion
  5–6 Isochoric cooling (Qo)
  6–1 Isobaric cooling (Qo')
caption: Figure 1: Atkinson gas cycle
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