As a result, the fuel may “hang around” a port for as long as 150 milliseconds when the engine is idling. Though basic MPFI employs multiple injectors, they all spray their fuel at the same time or in groups. Sequential fuel injection, also called sequential port fuel injection (SPFI) or timed injection, is a type of multiport injection. Also, where conventional metal intake manifolds must be located atop the engine to conduct heat, those used in MPFI can be placed more creatively, granting engineers design flexibility. Incremental fuel-economy improvements result. This is unnecessary on engines equipped with MPFI, so the intake manifold can be formed from lighter-weight material, even plastic. With TBI and carburetors, the intake manifold must be designed to conduct the engine’s heat, a measure to vaporize liquid fuel. Also, it virtually eliminates the possibility that fuel will condense or collect in the intake manifold. The main advantage is that MPFI meters fuel more precisely than do TBI designs, better achieving the desired air-fuel ratio and improving all related aspects. Shooting the fuel vapor this close to the intake port almost ensures that it will be drawn completely into the cylinder. Multipoint fuel injection devotes a separate injector nozzle to each cylinder, right outside its intake port, which is why the system is sometimes called port injection. Though not as precise as the systems that have followed, TBI meters fuel with better control than a carburetor and is less expensive and easier to service. For some automakers, single-point injection was a stepping stone to the more complex multipoint system. The earliest and simplest type of fuel injection, single-point simply replaces the carburetor with one or two fuel-injector nozzles in the throttle body, which is the throat of the engine’s air intake manifold. Related: Do Fuel Injectors Need Periodic Cleaning? Single-Point or Throttle-Body Injection
Single-point or throttle body injection.The fuel injection types used in newer cars include four basic types: CARS.COM - You’ve heard the term before, but what are the actual nuances of fuel injection? What are the different types of fuel injection in your vehicle? It requires a little bit of basic engine understanding, but we’re here to help.
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