Fuel injection system for internal combustion engine

In a port fuel injection lean burn engine, attaching of fuel spray onto a wall surface, which is a problem at atomizing injected fuel, is reduced, and the quality and shaping state of the mixed gas in cylinders of the engine is improved. The engine comprises a fuel injector (1); an intake valve (6) for opening and closing an intake port; and an intake air flow control device (10). The injected fuel is shaped in a low penetration fuel spray when the engine is operated in a low load and low rotation speed, and the injected fuel is shaped in a high penetration fuel spray when the engine is operated in a high load and high rotation speed, the fuel is injected in synchronism with the intake stroke of the engine, and is transported by the air flow flowing through the intake air flow control device (10) to suppress attaching of fuel spray onto a wall surface.