Engines, steam, or internal combustion, have been around for more than a century now. It took no time for the engineering majors to realize the inferiority of steam engines. And in no time, internal combustion engines took over. But even these engines needed to evolve, nurture into more efficient and less poison emissive. Since its inception, engine technologies have added power, performance, and efficiency. Fuel is injected in small pressurized pots, burnt, and churn out power with all those mechanical units. But the important part of the food to these engines is the fuel. And it’s crucial to seek advancement in spitting fuel in the cylinders in the most efficient manner.
The fuel injection parameters define the type of engine, power, efficiency, and some more engineering definitions that we’ll be skipping to avoid jumping into boredom. So why not learn about carburetors and fuel-injection technologies.
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Carburetors have been replaced by fuel injection in modern vehicles, but it was an effective way to dump fuel just a few years back. The basic working principle of a carburetor is related to a Venturi tube. It has a narrow section in the middle, which decreases the air pressure, and creates a vacuum. This vacuum venturi effect helps to suck out fuel from the fuel chamber. Like in the above diagram, the carburetor has two working valves: a choke and a throttle valve. The choke valve, decreases the air volume, increasing the fuel mixture, thus sprinkling rich fuel in the cylinders. This is ideally used during winters or a cold start.
The throttle valve or butterfly valve is controlled in sync with the accelerator, and it regulates the amount of air-fuel mixture that goes into the cylinder. The more the throttle is opened, the more air-fuel mix reaches the cylinder, hence more power, the faster the vehicle moves.
The fuel that comes out of the jet, as shown in the above figure, doesn’t come out randomly, it is precisely calibrated to meet the stoichiometric ratio, for maximum performance and efficiency. A stoichiometric mixture is the ratio of the mass of the air to the mass of the fuel, also known as the ideal air-fuel mix, where both oxygen and fuel combust at maximum efficiency. Attached beneath the carburetor body is the Float-Feed Chamber which is sort of a secondary fuel tank that feeds fuel to the engine. When the fuel level drops to a low, the float triggers a valve to refill the chamber.
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In modern-day vehicles, fuel injection has replaced outdated carburetors. An electronic fuel injection consists of an array of injectors or nozzles, oxygen sensors an electric fuel pump with a pressure regulator. An ECU or electronic control unit of the vehicle takes control over the amount of fuel to be injected into each cylinder, which is also the reason that fuel injectors are more efficient.
The fuel injection technology uses a pump to deliver the fuel. However, there is no prior mixing of air or even achieving air-fuel ratio. The air and the fuel entering the chamber are electronically regulated by an onboard computer that stores a “map” of the optimal settings. There is a fuel injector in each cylinder spraying fuel at the intake manifold. Thus these fuel injectors can change ratios of air-fuel mix according to the in-demand performance and efficiency. The fuel entering the engine is then atomized and vaporized for better ignition.
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The carburetors have been graved a long time ago, by none other than fuel injectors. But how do these modern-day injectors any better than conventional carburetors?
Let’s judge them on different parameters given below:
Versatility- The fuel-injectors are versatile, which means they are fit for both petrol and diesel engines, while the carburetor’s functionality remains to petrol engines only. Diesel injection requires fuel squirting at a certain pressure.
Performance- When it comes to performance, the carburetor is only dependent on the action of the throttle valve. While the fuel-injectors are controlled electronically and are guided by onboard computer-stored maps. Thus the ECU can sense the demand for more power and inject more fuel for more power.
Fuel economy- Again, the carburetors are limited to the throttle valve, which means the more the valve is open, the more fuel is dumped by the jet. While in the case of fuel injectors, the ECU can sense the throttle position and deliver maximum efficiency.
Maintenance- This is the only scenario where the carburetors beat the fuel injectors, as the simple construction of the former hardly requires any maintenance.
Reliability- When it comes to reliability, the fuel injectors being electronically controlled and consisting of complex electronics, are more reliable for performance and efficiency than carburetors.
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Yeah, there are more than one type of carburetors and each one serves a purpose, while the next one is generally the upgraded version.
Single body or throttle body injection - As the name is self-explanatory, the throttle body injection system has one or two fuel injectors in the throttle body. It replaces the conventional carburetors which were dependent on the throttle valve only and the air-fuel mix remained constant. The TBI meters better efficiency over carburetor, better control, is less expensive, and easier to maintain.
Port or Multipoint fuel injection- The port or multi-point fuel injection devotes a separate injector to each cylinder, right outside its intake port. They make sure that fuel vapors are completely drawn into the cylinder easily. These outperform TBI by achieving desired air-fuel mixture, and improving all related aspects; performance, and efficiency majorly.
Sequential fuel injection- Though multipoint fuel injection was progressing over TBI and carburetors, they had a major shortcoming. They would inject the fuel at the same time, and the fuel would hang around the ports for 150 milliseconds, which reduces the efficiency. The sequential fuel injection timed with the spark plug, injecting fuel just before the power stroke. This improves both efficiency and emissions.
Direct injection- These are mostly reserved for diesel engines, and here the injectors squirt the fuel directly into the cylinder where the air has just entered the chamber. These increase the efficiency and reduces the emission drastically.
With this, we have recollected the major facts about carburetors and fuel-injection and how the latter is more efficient than carburetors. The fuel injection system has further classified into types. Direct injection systems are majorly used in the industry for their efficiency and reduced emissions and are more reliable than any other fuel-injection technology.