Method and system for internal combustion engine

A method for operating an improved internal combustion engine unit, the engine unit having a piston moving in a cylinder enclosing cylinder volume, an intake valve controlling closing and opening of an intake aperture connecting the cylinder volume to an intake manifold, and an exhaust valve controlling closing and opening an exhaust aperture connecting the cylinder volume to an exhaust manifold, the improved engine unit further comprising a separating aperture between the cylinder and a separation chamber, and a separating valve for controlling closing and opening said separating aperture, the separation chamber being connectable to the intake manifold and to the exhaust manifold respectively by the intake and exhaust apertures, the method of operating the improved engine unit comprising:

• (a) opening said separating valve and while said separating valve is open:
• (i) opening the exhaust valve, enabling combusted gas flow from the cylinder volume to the exhaust manifold through the open separating aperture, the separation chamber and the open exhaust aperture;
• (ii) closing said exhaust valve for stopping said combusted gas flow;
• and
• (iii) opening the intake valve, enabling gas flow from the intake manifold to the cylinder volume through the open intake aperture, said separation chamber and said open separating aperture, and;
• and
• (b) closing said intake valve and closing said separating valve,
• thereby stopping gas flow from said intake manifold, isolating said separation chamber from the cylinder volume during compression and combustion strokes, and providing double isolation of said intake manifold and said exhaust manifold from the cylinder volume during compression and combustion strokes.