At present, a patented technology of energy-saving engine in China has successfully achieved all the indexes of hcci engine. The patent name is: intake and exhaust interconnected piston supercharged engine, and the patent number is 20 1 120375693.4. When the engine is turned off, the air in the closed cylinder is injected into the working cylinder nearby through the intake and exhaust connecting pipe to increase the compression ratio of the working cylinder. The purpose of gasoline compression ignition is achieved without ignition (without spark plug ignition), and the heat energy utilization efficiency is improved in detail, which is 30% higher than that of ordinary engines. In the energy-saving (cylinder closed) state, when the piston rotates around the crankshaft, fresh air will still be sucked in. This technology is skillfully used. The circulation of air in the engine meets the requirements of air uniformity of hcci engine, and the engine is not changed much, so the engine runs better in the closed cylinder state. When the cylinder is closed, the maximum engine speed is above 4,000, which can completely reach the maximum speed 1.20/ hour defined by China highway at present. The engine can be easily switched and operated between the normal combustion state and the closed cylinder hcci state through various sensors.