Difference Between Carburetor and Fuel Injection

Carburetor vs Fuel Injection
 

In an internal combustion engine, the fuel- air ratio of the fuel air mixture has significant influence on the performance of the engine, since it directly controls the power output of the engine.

Carburettors and Electronic fuel injection systems are devices used to mix fuel and air with a proper ratio and control the fuel air mixture given to the engine. The carburetor was first introduced in the late 19th century and the fuel injection methods came into the field around 1920`s. However, it’s only after 1980`s that the fuel injection systems completely overtook the carburetors in engine design.

More about Carburetors

Carburettor is a mechanical device used to control the fuel air mixture in any type of internal combustion engine. When it was first developed it was an ingenious design and served as the fuel control unit for almost a century.

The mechanism of the carburettors involves Venturi effect taking place in a narrow section of the air intake, where the increase in the airspeed causes a drop of pressure in the air flow. In this section, fuel is sucked out of a supply container through a small opening, and the container is connected to the main fuel tank with the flow controlled by a float valve mechanism. The air intake (volume flow rate) is basically controlled by a butterfly valve and acts as the throttling mechanism of the engine. When higher rate of air flow is present, more fuel is sucked out to deliver more power in the combustion, and the at lower flow rate it is the opposite. So this mechanism is used to control the power output of the engine, by basically starving or enriching the fuel mixture available to the combustion. In addition, mechanisms for start up an idle engine conditions are also provided.

Carburettors have been long used because of their ease to rebuild and make alterations. Also, if the engine is purely oriented for power, then the carburettor is the choice because it offers no limitation to the amount of the fuel drawn from the tank.

Despite its ingenious design and long service record, the carburettors have major drawbacks in terms of efficiency, performance at extreme and critical conditions. The high rate of emissions, lesser fuel economy, and the complexity of the system require experience to fine tune the system. In aircraft engines, the high acceleration during the flight maneuvers may cause fuel starvation to the engine, because of the mechanical design of the carburettor.

More about Fuel Injection

Fuel injection systems are used as a solution to the disadvantages of the carburettor and have become the most prominent type of fuel delivery system in the internal combustion engines.

The design of the fuel injection mechanism is extremely simple, but many parts are involved, which are heavily interdependent. A valve controlled by the input of a sensor or a similar mechanism connected to the throttle and the airflow allows pressurized fuel into the airflow to the engine.

Nowadays most common type of the fuel injection method is Electronic fuel injection (EFI), which uses a closed loop control cycle involving the engine control unit (ECU), many sensors, and the fuel injector unit. Based on the inputs from the sensor, the engine control unit actuate the injector.

Fuel injectors have many advantages over the carburettors. The fuel consumption can be optimized to suit the performance of the engine, hence increasing the efficiency and reducing the emissions. It can also allow the engine to perform with various fuels, and the operation from the driver’s perspective is smooth and fast. The complete electronic nature of the EFI allows problems to be diagnosed simply connecting the ECU to a diagnostic device or a computer. EFI is very reliable, and maintenance costs are also low.

What is the difference between Carburettor and Fuel Injection?

• Carburettors are completely mechanical devices, but fuel injection can be either mechanical or electronic. However, the electronic fuel injection (EFI) has become the most used.

• Carburettors are very complex, and specific experience is required for maintenance and tuning, but fuel injection mechanisms are simpler.

• The cost of a carburettor engine is lower than an EFI engine.

• Emissions from EFI system are very much lower than that of a carburettor used engine.