What Are the Difference Between Carburetor and Fuel Injector?

What Are the Difference Between Carburetor and Fuel Injector?

                     A carburetor is a device that blends air and fuel for an internal combustion engine. The carburetor comes from the French carbure meaning 'carbide'. To carburete means to combine with carbon. In fuel chemistry, the term has a more specific meaning of increasing the carbon content of a fuel by mixing it with a volatile hydrocarbon. Too much fuel in the fuel-air mixture is referred to as too rich, and not enough fuel is too lean. The mixture is normally adjusted by one or more needle valves on an automotive carburetor or a pilot-operated lever on piston-engined aircraft.

                      The air to gasoline ratio is 14.7:1, meaning that for each weight unit of gasoline, 14.7 units of air will be consumed. the air-fuel mixture is different for various fuels other than gasoline. To check carburetor mixture adjustment include: measuring the carbon monoxide, hydrocarbon, and oxygen content of the exhaust using a gas analyzer, or directly viewing the color of the flame in the combustion chamber through a special glass body, spark plug sold under the name 'color tune for this purpose. The flame color of stoichiometric burning is described as a 'bunsen blue', turning to yellow if the mixture is rich and whitish-blue if too lean. The mixture can also be judged after the engine running by the state and color of the spark plug; black, dry sooty plugs indicate a too rich mixture, white to light grey deposits on the plugs indicate a lean mixture. The correct color should be a brownish gray.

                      Most American market vehicles used special feedback carburetors that could change the base mixture in response to signals from an exhaust gas oxygen sensor. These were mainly used to save costs but eventually disappeared as falling hardware prices and tighter emissions standards made fuel injection a standard item. where multiple carburetors are used the mechanical linkage of their throttles must additionally be adjusted to synchronism for smooth engine running.

                      MPFI is used in gasoline/petrol Engines. For diesel engines, there is a similar technology called CRDI. MPFI system uses a small computer to control the car's engine. A petrol car's engine usually has three or more cylinders or fuel-burning zones. So in the case of an MPFI engine, there is one fuel injector installed near each cylinder, that is why they call it multi-point fuel injection. Before the MPFI system was discovered, there was a technology called 'carburetor'. The carburetor was one chamber where petrol and air were mixed in a fixed ratio and then sent to cylinders to burn to produce power. This system is purely a mechanical machine with little or no intelligence. It was not very efficient in burning petrol, it will burn more petrol than needed at times and will produce more pollution. But with the advancement of technology, this was changed.  MPFI emerged as an intelligent way to do what the carburetor does. In the MPFI system, each cylinder has one injector. Each of these injectors is controlled by one central car computer. This computer is a small microprocessor, which keeps telling each injector about how much petrol and at what time it needs to inject near the cylinder so that only the required amount of petrol goes into the cylinder at the right moment.

                      There is the major key difference is that MPFI is an intelligent system and carburetor is not. MPFI system is controlled by a computer which does lots of calculations before deciding what amount of petrol will go into what cylinder at a particular point in time. It makes that decision based on the inputs it reads. For the inputs, the microprocessor reads several sensors. Through these sensors, the microprocessor knows the temperature of the engine, The speed of the engine, it knows the load on the engine, it knows how hard you have pressed the accelerator, it knows whether the engine is idling at a traffic signal or it is actually running the car, it knows the air pressure near the cylinders, it knows the amount of oxygen coming out of the exhaust pipe. Based on all these inputs from the sensor, the computer in the MPFI system decides what amount of fuel to inject. Thus it makes it fuel-efficient as it knows what amount of petrol should go in.

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