Carburetors and fuel injection systems are very similar terms that perform similar functions. Their basic function is to regulate the mixture and emission of air and fuel. This, thereby, regulates the speed of the automobile.
However, while carburetors work mostly with motorcycles and old model cars, fuel injection systems replace carburetors in modern cars. In this article, you will learn more about a carburetor and fuel injector system and how they work.
What are carburetors?
It is the job of a carburetor to mix fuel and air for combustion. At all times, a particular mixture has to be maintained for the smooth running of the engine.
There are other components that work together with the carburetor to maintain the mixture ratio. The carburetor, however, regulates the amount of air and fuel mixture in the internal combustion system. This in turn this controls the speed of the vehicle’s engine. When the driver presses the accelerator of the vehicle, the valve moves and opens more.
This allows a larger quantity of the air and fuel mixture into the engine. It, therefore, causes it to run faster. Consequently, when the accelerator is eased, the valve closes a little.
When this happens, less mixture is let into the engine, thereby, causing it to slow down. When idling your vehicle at lower speeds, the throttle only has to stay open a little bit. This way, there isn’t a lot being pulled in through the valve.
What are Fuel injectors?
A fuel injector is a device present in modern petrol (GDI) and diesel (CRDI) engines that release a precise amount of atomized fuel into the combustion chamber. This release depends upon how fast the engine is rotating. Fuel injector systems are delivery systems that use a fuel injector to deliver pressurized fuel to the engine after atomizing it.
This process is controlled by a computer system in the vehicle. This ensures fuel is sprayed evenly to make burning easy and fast to keep the engine running smoothly.
A throttle present in each cylinder receives the atomized fuel through its intake manifold. Fuel injectors are electronically controlled to inject a precise amount of fuel. This helps in getting better fuel economy (more miles per gallon), especially in diesel engines.
There are sensors that monitor and report back to the computer to regulate the rate of fuel injected and burnt. These sensors must be working properly at all times for your car to operate properly.
How do the carburetors work?
Air enters the carburetor via the intake which is located at the top part of the carburetor. The air is filtered along the way inside the carburetor to eliminate dirt particles and cleanse the air. To start a car engine, a choke automatically blocks almost all the air is blocked from passing through the carburetor.
This reduction of air causes a significant rise in fuel present in the mixture entering the cylinders. This richer mixture of fuel helps the engine start especially from a cold position. A valve attached to the accelerator regulates the amount of air and fuel that flowing into the engine.
Whenever the accelerator is stepped on, the valve opens more and more air and fuel mixture flows into the cylinders. This produces more power for your engine, causing the car to move faster. When the driver steps off the accelerator, the reverse happens and power in the engine is reduced causing it to slow down.
Since the fuel is contained in a separate tank, a float is present in carburetors to regulate the flow of fuel from the tank. As the fuel chamber in the carburetor fills up, the floater reduces and stops fuel from entering. In the same way, as it drains, it lets fuel back in. Also, the fuel in the fuel tank is brought into the carburetor using suction. This is a little complicated process. Watch the video below to see just how carburetors work.
How does the fuel injector work?
The fuel injector is a very crucial part of the internal combustion engine which relies on direct injection. They are small electromechanical devices used to spray fuel into the intake manifold directly in front of the intake valve.
In fuel-injected engines, the fuel is pumped out of the fuel tank with the help of a Fuel-Pump. The Fuel Pump extracts the fuel at very high pressure. The air which enters the ‘Throttle Body’ via the airbox is controlled by the throttle movement. There is a butterfly valve that opens and closes with the throttle input.
The ECU or Electronic Control Unit in modern vehicle engines is the main head behind the combustion process. The ECU takes various signals from the sensors placed at the inlet of air, the temperature of the engine, oxygen sensor, etc. It knows exactly how much air is going in and how much fuel is required to complete that cycle.
The fuel injector is placed very close to the inlet port of the cylinder. It is a small needle-like structure with a very precise and small head that sprays fuel inside the cylinder.
The air enters the ECU, gets the values, and sends the fuel inside at very high pressure. The fuel mixes with the air and the spark ignites it. For every cycle and different loads, the requirements are different. The ECU, therefore, controls all of that using the information gathered from the sensors. Watch the video below to see how Injection systems work.
Advantages of the carburetor
Easy and Cheaper to Tune
The carburetor is easier to tune because it lacks absolute precision by default, which is an added advantage. Because of this, it will respond uniquely to every possible adjustment. Its margin of error is, therefore, bigger than what the fuel injector system can tolerate.
Also, there is no restriction on the amount of fuel drawn to the cylinder from the float chamber. It can provide a denser mixture at high speed for great power. To re-jet, the carburetor is easy and costs $50 or below.
To adjust for modifications of a carburetor, you simply swap in some new needle valves and jets from your kit. The most important feature of the carburetor is its low cost. This is reflected in its low purchase value, maintenance, and modification.
Advantages of Fuel injection systems
Adapts to Altitude
When there is a change in altitude, there is also a change in the engine’s performance. When operating an engine using a carburetor and there is a change in altitude, the operators would need to manually change the jetting of the carburetor.
In EFI however, the ECU detects a change in altitude through the air temperature and density sensor. It then automatically adjusts the fuel flowing through the injectors accordingly. This provides the perfect mixture ratio for the engine to keep running optimally at that altitude.
Improved Mileage & reduced emissions
The ECU reads the engine sensor then determines the exact amount of fuel and air mixture to be delivered by the injector. It activates the injectors for a precise amount of time then shuts them off.
This precision in delivery brings about an improved fuel economy and a reduction in vehicle emissions. The fuel injection service, therefore, helps provide vehicle owners with the mileage they achieved when they first bought their vehicle.
Absence of carburetor float problems
Floaters are present in carburetors to regulate the fuel passing through. Sometimes, however, these floaters get stuck and either block the fuel from passing through partially or completely.
They sometimes get stuck and can’t stop the fuel from flowing in, thereby, causing the excess to be present in the cylinder. But an EFI is completely electronic and has an injector, so it simply turns ON or OFF the injector.
Reduced Risk of Vehicle Breakdowns
Here the entire fuel system is sealed very well so as to prevent the gasoline (petrol) from coming in contact with oxygen. This damages the injection system. So there is less replacement or maintenance experienced with injection systems, unlike carburetors. This in turn reduces car expenses.
The brain of the Electronic fuel injection (EFI) engine is the Engine control unit (ECU). This ECU is the reason for many advantages of EFI. The ECU collects, reads, and interprets the information it receives from sensors. This way, it monitors different parameters in the engine so it can efficiently.
Why did carburetors Phase-out of vehicles?
Initially, the cars with gasoline (petrol) engines, were the first to omit carburetors. Due to advancements in vehicle engine technology, it became common that a car has more than one cylinder.
The problem is that each cylinder must have its own carburetor to function. If it is a 4 cylinder petrol engine then you need 4 carburetors with separate air intake and separate filters. This would, therefore, result in increased cost, space required, and an increase in engine size.
Below Other Reasons :
- The carburetor wasn't able to quickly respond to the driver’s intentions. This, therefore, resulted in unmatched performances and became more obvious when the demand for high-performance vehicles increased.
- Since air controls the intake of fuel via suction, there is more chance that the air will move faster into the cylinder leaving the fuel behind it.
- Carburetors limit the number of air-fuel ratios that can be followed. This causes inconsistencies when there is a need to adjust. They generally use various jets (passages to supply fuel when required), to take care of driving under heavy loads and wide-open throttles.
- They were a bit larger when compared to fuel injectors.
- It is a purely mechanical-based system, and this alone had its own limitations.
- Still, most bikes (at least in India) are using carburetors as the emission norms are a bit lean here.
- Regulations on vehicular emissions were becoming tighter and stricter, but some motorbikes still use them.
It is important to note that the 1991 Jeep Grand Wagoner was the last car built with a carburetor in America.
Comparing carburetors to fuel injection
Since the carburetor is a purely mechanical device, it was unable to measure the changing air pressure and fuel temperature so as to correctly tweak and supply the correct air to fuel ratio. This is something that is very easy for the fuel injection system to achieve. It achieves this because it is electronically controlled. It, therefore, constantly tweaks the mixture delivered into the cylinders, thereby, resulting in a better performance.
Due to its purely mechanical nature, the carburetor is unable to adjust the fuel to air ratio according to changing engine conditions. The fuel injection system, however, constantly measures the ever-changing engine parameters. This way, it supplies the precise amount of fuel the engine needs to function properly. This results in less fuel wastage and better all-around fuel efficiency.
This is the only area the carburetor has an upper hand over the fuel injection system. This is because carburetors being purely mechanical are easy to dismantle, clean, and rebuild when they have performance issues. A faulty fuel injection system, on the other hand, requires professional attention and most times, and outright replacement.
Carburetors had a lot of setbacks. One is the fact that it does not function in diesel engines. Fuel injection, however, works well and efficiently for both gasoline (petrol) and diesel engines in electronic and mechanical variation. This flaw caused the carburetor to be phased out of the automobile industry by the mid-1990s and replaced with the growing popular fuel injection.
Dealers, for instance, sell an Edelbrock 1406 Performer 600 carburetor for around $368. Whereas, an Edelbrock 35760 Pro-Flo 4 fuel injection kit goes for around $1,895. The price gap is staggering but is a good investment. This is because the EFI (electronic fuel injection) will typically run four to five times more than its carburetor equivalent.
Which is the better option?
The Fuel injection system is obviously a better option. Due to stricter regulations on emissions, most automobile industries switched and more will continue to switch to fuel injection systems. This is to save our environment from air pollution and degradation. Because of the high cost of fuel injection systems, however, some will still remain loyal to carburetors.
Engines can generate more horsepower because of the ability of the fuel injection system to constantly alter the fuel and air supplied. This in turn means vibrations experienced by the engine are greatly reduced.
This Is because it doesn’t need to overwork to burn the excess fuel present while doing minimal work. Also, it overcomes very steep terrains better due to its flexibility.
- Both systems are good but the injection system is better.
- Carburetors are present in a very little percentage of modern cars.
- The 1991 Jeep Grand Wagoner was the last car built with a carburetor in America.
- Carburetors even though cheaper, injection systems are better for the long term.
- DIYers cannot service Fuel injection systems because of their complexity. Users must visit professional auto mechanics.