Three-point-nine-liter diesel engine

The utility model provides a three-point-nine-liter diesel engine. The three-point-nine-liter diesel engine comprises an engine air cylinder body and four air cylinders in the engine air cylinder body, the four air cylinders are arranged in an in-line mode, and each air cylinder comprises a piston, a piston ring, a burning chamber and air valves; the diameter D of the air cylinders ranges from 100 mm to 110 mm; the piston stroke S ranges from 105 mm to 125 mm; the total displacement Vh of the engine is equal to 3.9 +/- 0.1 liters. The number of the air valves of each air cylinder of the engine ranges from two to four. The number of piston rings of the engine ranges from two to four. The piston burning chambers are in a direct spraying mode. The structural type of air cylinder sleeves of the engine is the dry type. Auxiliary cylinder gaps between pistons of the engine and the air cylinder sleeves range from 0.12 mm to 0.15 mm. The axial backlash of piston top rings of the engine ranges from 0.10 mm to 0.14 mm. The cooling mode of the engine is the water cooling mode. The air inlet mode of the engine is the supercharged air inlet mode, the supercharged water-air intercooling air inlet mode or the supercharged air-air intercooling mode. According to the three-point-nine-liter diesel engine, through matching of an engine burring system and optimizing of an electronic control high pressure common rail fuel injection system, the dynamic property and the fuel economic property of the engine are improved.