Six-stroke engine high level of efficiency (US Patent 4.809.511 & 4.513.568) 1st. stroke Intake of pure air in the cylinder (5). The valve (1) is open. 2nd. stroke Compression of pure air in the heating chamber (7). The valve (2) is open. 3rd. stroke, power stroke (work) Release of combustion gases in the cylinder (5). The valve (3) is open. 4th. stroke Exhaust of the combustion gases. The valve (4) is open. 6th. stroke Recompression of the pure air in the heating chamber. 5th. stroke, power stroke (work) Release of pure air into the cylinder (5). Six-stroke engine explanations During the 1st. and the 2nd. strokes, the air in the combustion chamber (6) can receive the injection of fuel and ignition is triggered. During the 3rd. and the 4th. strokes, the temperature of the pure compressed air in the heating chamber (7) is sharply raised by heat exchange from the combustion chamber (6). 1. Intake valve 2. Heating chamber valve 3. Combustion chamber valve 4. Exhaust valve 5. Cylinder 6. Combustion chamber 7. Air heating chamber 8. Wall of combustion chamber 9. Fuel injector 10. Heater plug