Editing Otto cycle (section)

==Processes==
The processes are described by:<ref name="Shapiro" />
*Process 0–1 a mass of air is drawn into piston/cylinder arrangement at constant pressure.
*Process 1–2 is an adiabatic (isentropic) compression of the charge as the piston moves from bottom [[Dead centre (engineering)|dead center]] (''BDC'') to top dead center (''TDC'').
*Process 2–3 is a constant-volume heat transfer to the working gas from an external source while the piston is at top dead center. This process is intended to represent the ignition of the fuel-air mixture and the subsequent rapid burning.
*Process 3–4 is an adiabatic (isentropic) expansion (power stroke).
*Process 4–1 completes the cycle by a constant-volume process in which heat is rejected from the air while the piston is at bottom dead center.
*Process 1–0 the mass of air is released to the atmosphere in a constant pressure process.

The Otto cycle consists of isentropic compression, heat addition at constant volume, isentropic expansion, and rejection of heat at constant volume. In the case of a four-stroke Otto cycle, technically there are two additional processes: one for the exhaust of [[waste heat]] and combustion products at constant pressure (isobaric), and one for the intake of cool oxygen-rich air also at constant pressure; however, these are often omitted in a simplified analysis.  Even though those two processes are critical to the functioning of a real engine, wherein the details of heat transfer and combustion chemistry are relevant, for the simplified analysis of the thermodynamic cycle, it is more convenient to assume that all of the waste-heat is removed during a single volume change.