Automobile Engine Fuel Injector

For most of the life of the internal combustion engine, the carburetor has been the piece of equipment that supplied fuel to the engine. On many other machines, such as lawnmowers and chainsaws, it still is. But as automobile engines evolved, the carburetor got more and more complicated trying to handle all of the operating requirements. For instance, to handle some of these tasks, carburetors had five different circuits:

* Main circuit
* Idle circuit
* Accelerator pump
* Power enrichment circuit
* Choke
In order to meet stricter emissions requirements, catalytic converters were invented. Very careful control of the air-to-fuel ratio was required for the catalytic converter to be effective. Oxygen sensors monitor the amount of oxygen in the exhaust, and the engine control unit (ECU) uses this information to adjust the air-to-fuel ratio in real-time. This is called closed loop control — it was not feasible to achieve this control with carburetors. There was a brief period of electrically controlled carburetors before fuel injection systems took over, but these electrical carbs were even more complicated than the purely mechanical ones.

At first, carburetors were replaced with throttle body fuel injection systems that incorporated electrically controlled fuel-injector valves into the throttle body. These were a bolt-in replacement for the carburetor, so the automakers didn’t have to make any drastic changes to their engine designs.

Gradually, as new engines were designed, throttle body fuel injection was replaced by multi-port fuel injection. These systems have a fuel injector for each cylinder, usually located so that they spray right at the intake valve. These systems provide more accurate fuel metering and quicker response.

When You Step on the Gas, the gas pedal in your car is connected to the throttle body, this is the valve that regulates how much air enters the engine. So the gas pedal is really the air pedal.

A partially open throttle valve When you step on the gas pedal, the throttle valve opens up more, letting in more air. The engine control unit “sees” the throttle valve open and increases the fuel rate in anticipation of more air entering the engine. It is important to increase the fuel rate as soon as the throttle valve opens, otherwise, when the gas pedal is first pressed, there may be a hesitation as some air reaches the cylinders without enough fuel in it.

Sensors monitor the mass of air entering the engine, as well as the amount of oxygen in the exhaust. The ECU uses this information to fine-tune the fuel delivery so that the air-to-fuel ratio is just right.

Read more about fuel injection systems in our next bog post. Education is fun, it also makes a better consumer. Enjoy. GotEngines.com @ 1-888-344-8044.