Six-stroke engine  high level of efficiency (US Patent 4.809.511 & 4.513.568) External combustion cycle : (divided in 4 events)
No direct contact between the air and the heating source.
e1. (Event 1) Pure air intake in the cylinder (dynamic event). 
e2. (Event 2) Compression of pure air in the heating chamber (dynamic event). 
e3. (Event 3) Keeping pure air pressure in closed chamber where a maximum heat exchange occurs with the combustion chambers walls, without direct action on the crankshaft (static event). 
e4. (Event 4) Expansion of the super heated air in the cylinder, work (dynamic event). Internal combustion cycle : (divided in 4 events)
Direct contact between the air and the heating source.
i1. (Event 5) Re-compression of pure heated air in the combustion chamber (dynamic event) 
i2. (Event 6) Fuel injection and combustion in closed combustion chamber, without direct action on the crankshaft (static event). 
i3. (Event 7) Combustion gases expanding in the cylinder, work (dynamic event). 
i4. (Event 8) Combustion gases exhaust (dynamic event).