It’s a good question and one that deserves an appropriate answer. For those people who remember carburetors in older cars or who still use them, there is a fondness for the old-style engineering. However, fuel injection has given us the means to increase fuel efficiency and meet the constantly changing standards issued by governments. Of course, there are those who miss the old carburetors, but there were a variety of reasons for ending their use in modern automobiles.
First, the carburetor was simply unable to keep up with the increased standards for fuel efficiency and exhaust emissions. As these standards increased, the older manual carburetors were replaced with electronically controlled carburetors. Unfortunately, these new carburetors became too complex for many cars to use and eventually needed to be replaced. Fuel-injection had been used in some high-performance cars, such as those used for racing, since the 1950’s and seemed to be what the automotive industry was looking for.
The single-point fuel injector was first used by automakers since it was easy to simply bolt into place where the carburetor would have been. Although a great advancement, automakers soon realized the need for multi-point fuel injectors that would individually deliver fuel to each cylinder. In doing so, the multiple injectors could more easily control the amount of fuel use while delivering that fuel as a fine vapor or mist. Since a vapor exposes more surface area of fuel to the oxygen present in the cylinder, the fuel will burn more efficiently and completely. The oxygen sensor in the exhaust system monitors the amount of oxygen leaving the cylinders and allows the car’s computer to adjust the richness of the fuel mixture.
The engine control unit (ECU) maintains control of the amount of fuel released by the fuel injectors. As you apply pressure to the accelerator pedal, an air throttle opens to allow air inside the engine. The ECU “sees” this opening and measures how much air enters the engine. Then, it uses this information to determine how much fuel to release through the injectors. A small electromagnet inside each injector causes a plunger to move, opening the end of the injector to allow a small amount of fuel to enter the cylinder valve directly. The amount of fuel needed determines how long the plunger remains open. Each cylinder has its own fuel injector and on occasion one or more injectors may need replacement as they age.