What is Throttle Body Injection
Thethrottle body injection(TBI) system is still traveling the roads inside the engine compartment of older vehicle models around the world. But not for long. Soon, it will be history. Back in the 1980s, the throttle body injection system came to take the place of carburetors, top and center on the vehicleintake system, because of its better handling and control of the air-fuel mixture. Automobile engines, however, were not the first to use it. Heavy aircraft began fitting their engines with a TBI model 40 years before, starting with the single point throttle body injection system.
The TBI system is a type of fuel injection system, just like the modern multiport fuel system. The TBI, however, can have one or two fuel injection valves right on the throttle assembly. On the other hand, a multiport system provides one injection valve for every cylinder on the engine, distributed around the intake system.
What makes up a throttle body injection system assembly?
The TBI system is made up of a few simple components. The housing itself holds the system assembly together. It includes the mounting surface for the injectors, the fuel pressure regulator, the throttle valves or injectors, and throttle plate to control the flow of air entering the engine. Besides these components, the assembly is equipped with a throttle position sensor to tell the computer the exact position of the throttle plates and a small electric motor to control the plates' position during idle. This simple configuration gave the vehicle’s computer a better control of the air fuel mixture than the carburetor could provide before.
How the TBI system works
Under the control of the vehicle'sengine control module(ECM) or computer, the injector sprays fuel into the top of the assembly or air horn. The computer energizes the valves inside the injector through an electrical circuit to provide fuel to the engine. The air and fuel mixture is then pulled into the engine by atmospheric pressure passed the throttle plates and by intake system vacuum created during engine operation.
TBI system types
Throttle body injection systems don't differ much. In general, this simple design may vary in the number of injection valves and the way fuel is injected into the intake system. A TBI can have one or two injectors on top of the assembly and most TBI systems use the modulated fuel injection model. Under this system, the computer sends a series of electrical pulses to the injector to energize the internal valve during engine operation. The continuous TBI fuel injection model, on the other hand, feeds an uninterrupted stream of fuel to the engine and uses a pressure variation on the injector’s valve to control the amount of fuel going into the engine.
Today, themultiport fuel injection systemoffers a better air fuel and emission control, which is the main reason all newer vehicle models are equipped with this system. Nevertheless, the throttle body injection system is still feeding thousands of engines worldwide. In fact, you can still find replacement parts for many of these models to keep them working as efficiently as originally intended. In a few years, though, the throttle body injection system will be off the roads to take its rightful place in automotive history. And the only place you will find them will be in an automotive museum in your town.
