Abstract: This application pertains to reciprocating piston engines supplied hot pressure fluid medium by combustion products pressure generators and controls thereof.This invention pertains to a new improved electro magnetic operated automatic, reversible cut off system for the pressure fluid medium admission valves to the power cylinders of reciprocating piston engines. To control the power and speed thereof. Controlled by speed governor or manual means.This invention pertains to a new improved electro magnetic operated automatic cut off system for the pressure fluid medium admission valves to the high pressure power cylinders of a reciprocating piston engine. Used as a pressure reducing means controlled by the pressure on the exhaust to the low pressure cylinders. This means is especially suitable where the pressure of the fluid medium varies widely.A combination of the two above described cut off control systems used together on a multi cylinder reciprocating piston engine.