TBI fuel injection is a type of fuel injection system where the fuel is injected into the throttle body. The throttle body fuel injection system, or TBI as referred, works using a single or pair of injectors. The throttle looks like a carburettor without the fuel bowl, the metering jets or the float.This type of fuel injection system consists of only two major castings - the fuel body and the throttle body. The fuel body supplies the fuel while the throttle body has a valve that controls the flow of air. On the throttle, there are ports that gather signals to relay to the manifold absolute pressure sensor and to the emission control system.