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Electronic Fuel Injection Throttle-Body Injection / Port-Injection
What: There are two types of fuel injection. Throttle-body (similar to carburetion) and port injection.
How: Throttle-body injection places the injectors in the airstream introducing the fuel into the air as it passes through the venturi similar to the way that a carburetor does. Port injection introduces the fuel into the airstream through ports in the manifold next to the intake valve. Port injection is more efficient because the fuel/air ratio is controlled directly before entering the cylinder but requires a special manifold, plumbing to route the fuel and devices that regulate the injection process. Throttle-bodies just mix the fuel with the air at the venturis the same as a carburetor does but regulates the fuel/air ratio more efficiently. Both systems are controlled by an ECM (engine control module); basically a preprogrammed computer that uses feedback information from sensors to set the optimum fuel/air ratio on a continuous basis.
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