Fuel injection is the introduction of fuel in internal combustion engines, mostly automotive engines, using injectors. This process was introduced to keep up with emissions and fuel efficiency laws. Over the years, car manufacturers saw great advantages of fuel injectors, which is where the downfall of carburetors began.
From 1980 onward, fuel injection became an alternative to carburetors on petrol engines. Well, the difference between fuel injection and carburetion is that fuel injection atomizes the fuel through a small nozzle under high pressure. Whereas carburetors rely on drawing fuel into the airstream through a venturi tube.
In this reading, we’ll explore what a fuel injection system is, its functions, parts, types, and how it works. We’ll also learn its advantages and disadvantages.
Let’s get started!
What Is A Fuel Injection System?
The fuel injection system detects the amount of air that enters the engine and gives the necessary fuel for combustion. An ECU controls the amount of fuel injected and the duration for which the fuel injection valves (injectors) remain open. It does this by calculating the amount of fuel to be injected based on signals from a sensor that measures the amount of air intake.
Before the existence of fuel injectors, carburetors have been highly used on engines, and to date, this engine still exists. In fact, many other machines, like lawnmowers and chainsaws, still use carburetors. But because the component got complicated trying to control all requirements on automobiles, a better alternative is released.
Furthermore, carburetors were first replaced with throttle body fuel injection systems. This system is also known as a single-point or central fuel injection system. It is electrically controlled fuel-injector valves into the throttle body.
This was almost the best alternative, which allowed auto manufacturers don’t have to make drastic changes to engine designs. Gradually, as new engines were designed, multi-port fuel injection replaced the throttle body fuel injection. This multi-port fuel injection is also known as port, multi-point, or sequential fuel injection.
In addition, the system contains a fuel injector for each cylinder, which sprays right to the intake valve. It provides more accurate fuel metering and quicker response.
Functions Of Fuel Injection System
The fuel injection system performs a notable function in a car. Below are the common functions of the system:
- The main purpose of fuel injection systems in diesel engines is that the components have a significant impact on their design.
- Fuel injectors help to deliver fuel to the cylinders.
- It enhances the engine in terms of performance, emission, and noise characteristics.
- Fuel is delivered under extremely high injection pressures.
- Its materials are designed to withstand higher stresses for durability that match the engine working.
- Another purpose of the injection system is that fuel is injected at the proper time. That is, the injection timing is controlled.
- The correct amount of fuel must be delivered to meet the power requirement of the engine. This is why the injection metering is controlled.
- Injectors are made of greater manufacturing precision and tolerance to ensure their working efficiency. It also avoids leakage.
- The fuel injector atomizes fuel into a very small fuel particle, ensuring every small droplet of fuel vaporizes and undergoes the combustion process.
- There is enough oxygen to mix with the atomized fuel, which ensures complete combustion.
Diagram Of A Fuel Injection System
Parts Of Fuel Injection System
The fuel injection system consists of several key components, each playing a crucial role in delivering the right amount of fuel to the engine. Here are the main parts:
Fuel Tank
Fuel goes into your fuel tank when you pump it. This holds fuel before it’s injected into the combustion chamber.
Fuel Pump
The fuel pump is a component that is located inside the fuel tank. In addition, the pump is often seen in the tank on modern cars. The fuel pump is responsible for pumping fuel into the engine. And the car’s battery is most likely what powers an electric pump mounted on the fuel tank. However, when the pump is outside, the motor’s movement powers it.
Fuel Filter
A working fuel delivery system depends on the fuel filter. This applies more to fuel injection than carbureted cars. Dirt can damage fuel injectors due to their close tolerances, but fuel-injected cars use electronic fuel pumps.
The electric fuel pump burns itself trying to push past a clogged filter. Cars usually have two filters. One in the gas tank and one at the fuel injectors or carburetor. Only the line filter needs to be replaced unless a severe and unique issue causes a lot of dirt to enter the gas tank.
Fuel Lines
Steel lines and flexible hoses transport fuel from tank to engine. Copper or aluminum cannot be used to service or replace steel lines. Replace steel lines with steel. Use the right hose when replacing flexible rubber hoses. Ordinary rubber, such as that used in vacuum or water hoses, softens and deteriorates. Keep all hoses away from the exhaust.
Fuel Injectors/Carburetors
The fuel injector is the final point for fuel delivery in your engine before it ignites within the combustion chamber. An electrically driven gate opens just long enough to give the engine the right amount of fuel. Most cars used carburetors until the late 1980s.
Manual, non-electric carburetors mix vaporized fuel with air to create a combustible or explosive mixture for internal combustion engines. Electronic fuel injection has replaced carburetors.
Intake Valve
The valve opens to draw air/fuel into the combustion chamber. Deposits on the intake valves can limit or alter the flow of air/fuel into the combustion chamber. Deposits on the intake valve might prevent fuel from entering the combustion chamber. Performance can be lost but can be regained with the help of the appropriate fuel additive.
Throttle Body
This part regulates the air entering the engine, controlling engine power and speed.
Combustion Chamber
The air/fuel mixture burns here. Combustion chamber deposits may have an impact on air/fuel compression and heat transmission. Excess heat might lead to early ignition and knocking. Some vehicles have knock sensors to detect engine knock or pre- or post-detonation.
These sensors allow the computer to detune the engine to eliminate this performance-degrading condition. It’s crucial to clean your fuel system since deposits cause knocking.
Piston
The pressure from combustion is converted into motion via the piston’s up-and-down motion. Effective detergent additives can decrease or eliminate deposit-related drivability and performance loss.
Engine Control Unit (ECU)
The ECU manages the fuel injection process by adjusting the timing and amount of fuel injected in response to engine conditions.
Related: What Is A Carburetor? Its Function and How It Works
Types of Fuel Injection Systems
Fuel injection systems can be classified into several types based on their design and operation. Here are the main types:
Single-Point or Throttle Body Injection
The single-point type of injection system is the earliest and simplest fuel injection that replaces carburetors. It contains one or two injector nozzles in the throttle body, which is the throat of the engine’s air intake manifold. This injector system is not as precise as the system that followed, but when compared with carburetors, it has better control, is less expensive, and is easier to service.
Port or Multiport Fuel Injection
In multiport fuel injectors, separator injector nozzles are contained in each cylinder at its intake port. This is why the system is sometimes called a port injector, shooting the fuel vapor close to the intake spot, ensuring it’s completely drawn into the cylinder.
One of the benefits of this injector is that the meter’s fuel is more precise when compared with the single point. It is also perfect for achieving the required fuel-air ratio, and it virtually eliminates the possibility that fuel will condense or collect in the intake manifold.
Sequential Fuel Injection
This type of fuel injector is also known as sequential port fuel injection or time injection. It is a type of multiport injection, even as basic multiport uses multiple injectors. They all spray their fuel at the same time or sequentially, making the fuel hang around for as long as 150 milliseconds when the engine is idling.
The benefits of sequential fuel injection are that the system responds more quickly if the driver makes a sudden change. This is because the valve only has to wait for the next intake valve to open, rather than the complete revolution of the engine.
Direct Injection
Direct injection is common in diesel engines, although starting to be common in gasoline engine designs. It is sometimes called DIG for direct injection gasoline. In its process, fuel is injected directly into the combustion chamber, past the valves. Fuel metering is more precise than other fuel injection types. Direct fuel injection gives engineers another variable to influence precisely how combustion occurs in the cylinders.
The science of engine design examines how air-fuel mixture swirls around in the cylinders. And also how the explosion travels from the ignition point. Direct injection in a gasoline engine can handle things such as the shape of cylinders and pistons. Also, port and spark plug locations, timing, duration, and intensity of the spark. Number of spark plugs per cylinder. All these affect how completely and evenly fuel combusts in a gasoline engine.
How A Fuel Injection System Works
The working of a fuel injector system is quite interesting and easier to understand. The main work is from the fuel injector to the combustion chamber after fuel is pumped to it from the fuel tank. As earlier said, the fuel injector is an electronically controlled mechanical device that is responsible for fuel spraying. The injector gets energized and an electromagnet moves a plunger that opens the valve.
This valve allows the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel, which is responsible for making the fuel easily burn. The amount of time the fuel injector stays open will determine the fuel supplied to the engine. Additionally, an ECU device is in charge of controlling this, which is known as “pulse width.” Fuel injector systems are mounted directly to the intake manifold so that fuel can be sprayed directly into the intake valve.
There is a spring inside the conventional injector that holds the needle valve in a close position. It holds this needle valve until the high-pressure line meets a specific value. There is a pipe called a “fuel rail” that supplies pressurized fuel to the injectors. The right amount of fuel is supplied to the required parts.
Different parts of the engine are equipped with sensors that give information to the ECU about the amount of fuel and make adjustments if needed. The various sensor have been listed and explained in the above part of this article.
Advantages
Below are the benefits of the fuel injection system:
- A precise fuel mixture of fuel and air ensures maximum possible fuel efficiency and power production.
- The combustion process is significantly more efficient in fuel-injected engines.
- Fuel injection engines are more economical, and they maximize and minimize the emission level.
- Cold starting is eliminated in fuel-injected engines, making no need for manual chocking.
- It’s also used on modern performance motorcycles.
- The fuel injection system automatically balances the air-fuel mixture considering the environmental situation.
- Engine vibration is reduced, and the spark plug fouling issue is minimized.
Disadvantages
Despite all the benefits of the injection system, some limitations still occurs. Below are the disadvantages of the system:
- It is a complex electronic-controlled device that works with few electronic sensors.
- Maintenance and repair of the system are very limited. That is, not all workshops can do their work.
- The fuel injection system is quite expensive.
- Good-quality material and fuel are highly recommended.
- There is no solution for low cost and low capacity.