Five-stroke engine

The invention discloses a five-stroke engine. The five-stroke engine comprises a first cylinder, a second cylinder, an auxiliary cylinder and a boost mechanism, wherein an intake port and an exhaust port of the first cylinder are both connected with the boost mechanism; the exhaust port of the first cylinder is connected with an intake port of the auxiliary cylinder; an intake port and an exhaust port of the second cylinder are both connected with the boost mechanism; the exhaust port of the second cylinder is connected with the intake port of the auxiliary cylinder; and an exhaust port of the auxiliary cylinder is connected with the boost mechanism. The five-stroke engine realizes out-cylinder low-temperature pressurization, increases the intake density, relieves in-cylinder knocking phenomenon while satisfying the power requirement, improves the engine isometry degree, optimizes the combustion phase, improves the heat efficiency, and on the other hand, reduces the exhaust temperature, and protects turbine blades.