How Fuel Injection Engines Work

Wondering how fuel injection engines work? Since the early '90s every car sold in The United States has come equipped with a fuel injection engine. This is because fuel injection engines, which were introduced back in the 1950s, provide modern cars with improved acceleration and better gas mileage. Prior to this the most common method of delivering fuel to the engine was through a carburetor; however, due to its restrictive design and overly-complicated series of circuits, it was not able to compete with the more efficient fuel injection systems.

Fuel injection engines work quite simply, and it all starts with the gas pedal.  Contrary to its name, the gas pedal controls the flow of air, not the flow of gasoline. When the gas pedal is pushed down it opens the throttle valve, which allows air to move into the engine. A computer within the engine, known as the ECU (Engine Control Unit), measures the amount of air coming in and matches it with fuel from the injection system.

Essentially, a modern fuel injector is a valve controlled electronically by the ECU. The injector opens via an electromagnet plunger when the ECU needs to adjust the air-to-fuel ratio. Modern injectors are capable of opening and closing many times per second, with some high-end models capable of being tuned to the millisecond, which means there is a greater degree of accuracy when small adjustments need to be made. When the injector opens fuel is then atomized into a vaporous mist—allowing an it burn more easily—and then sprayed directly at the engine’s intake valves.  The amount of time the injector stays open is called the "pulse width"and is determined by a series of equations and look-up tables within the ECU.

The fuel makes its way into the cylinder via the intake valve and mixes with the air from the throttle valve. The piston within the cylinder moves upward and compresses the mixture so that the resulting explosion is more powerful. Once the piston is in position, the mixture of fuel and air is ignited by a spark from the spark plug. The force of the explosion drives the piston downward towards the exhaust valve, which opens to discharge any exhaust.  As the piston moves down it turns the crankshaft, which powers the vehicle and allows you to deliver pizzas, get to work on time, or take a joy ride through the mountains.

Once the piston is at its lowest point the fuel injection system sprays more fuel into the intake valve, and the whole process is ready to be repeated.