EFI means automobile engine is normally provided by injection passage, and an electronic control unit sensor group composed of three parts. An injector If 
mounted on the carburetor original position, i.e. the whole fuel injection engine is only a point, this is a single point fuel injection.
Since the single point injection injector is disposed above the throttle valve, can only improve the atomization and heating the wall temperature at the throttle improve the degree of evaporation of fuel, but it is difficult to ensure that after a period of intake throttle valve film is not formed on the tube wall or oil, the structure of the intake manifold of the mixture gas delivery
and dispensing a significant impact on, and can be difficult to achieve distribution to maintain the desired air-fuel mixture in all operating conditions.
However, single point injection structure is simple, reliable, easy to maintain. One very significant advantage is that a single point of injection is disposed above the throttle valve, a high velocity gas flow directly to the intake duct injection, since there is low pressure (flow rate inversely proportional to pressure), the injection only 0 .1 MPa low pressure spray can, and multi-point injection will have to work until at 0.35MPa, which means that single-point injection system can reduce the requirements for electric fuel pump, saving costs. However, emission standards and fuel economy is not a single point and multi-point EFI EFI is now also slowly being eliminated.