Rajan Wilcox
Fuel injection systems have been used in cars since the 1970s, replacing carbureted engines. There are several types of fuel injection systems, including electronic fuel injection (EFI), mass air flow fuel injection, throttle body injection (TBI), and port fuel injection. The type of fuel injection system in a car depends on various factors, including the make, model, year, and engine size. EFI systems, for example, are known for their precision in producing air-fuel ratios and are controlled by the powertrain control module (PCM). Direct injection systems deliver fuel directly to the cylinder heads, while port fuel injection systems have injectors in the intake manifold.
| Characteristics | Values |
|---|---|
| Ease of maintenance | Carburetors are easier to maintain than fuel-injection systems |
| Cost of maintenance | Fuel-injection systems are more expensive to maintain than carburetors |
| Complexity | Fuel-injection systems are more complex than carburetors |
| Performance | Fuel-injection systems are more precise than carburetors in producing air-fuel ratios |
| Engine issues | Carburetors may cause engine backfires, stalling, flooding, hesitation on acceleration, and other issues that may affect a vehicle’s drivability |
| Emission | Fuel-injection systems produce lower emissions than carburetors |
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What You'll Learn
- Carbureted engines have a single or double barrel, with one or two venturi operating
- Fuel-injected systems are more complex and costly to maintain
- Electronic fuel-injection (EFI) systems are more precise when it comes to producing air-fuel ratios
- EFI systems rely on the powertrain control module (PCM) to pulse the fuel injectors on and off
- Direct injection has fuel that goes to the cylinder heads
Carbureted engines have a single or double barrel, with one or two venturi operating
Carbureted engines are known to have a single or double barrel, with one or two venturi operating. The basic design for a carburetor consists of a single venturi (main metering circuit), but designs with two or four venturi (two-barrel and four-barrel carburetors) are also common. Single-barrel carburetors have only one venturi operating, while double-barrel carburetors have two venturi for additional power. There are also some vehicles that have four barrels, with two primary barrels always operating and the other two secondary barrels opening up at higher speeds.
The multiple carburetors result in the intake air being drawn through multiple venturi. Some high-performance engines have used multiple two-barrel or four-barrel carburetors. The venturi in a carburetor creates what is known as the Venturi effect, which describes the reduction in pressure from the airflow. This reduction in pressure draws fuel into the airstream. The speed of the air passing through the venturi increases at greater throttle openings, which lowers the pressure of the air and draws more fuel into the airstream.
The carburetor was once the simplest form of fuel delivery in an internal combustion engine. However, it eventually lost its popularity with the introduction of fuel-injection systems, which are much more efficient in calculating air-fuel ratios. Carburetors are relatively inexpensive and easier to maintain, clean, and modify when compared to fuel-injection systems. They can also be modified according to altitudes and driving styles. However, they are incompatible with diesel engines and struggle with changes in air pressure and fuel temperature.
Fuel-injection systems, on the other hand, are more precise when it comes to producing air-fuel ratios. They rely on the powertrain control module (PCM) to pulse the fuel injectors on and off and operate the fuel pump relay circuit. There are two types of EFI systems: throttle body injection (TBI) and port fuel injection. There are also two ways of measuring how much air the engine is taking in to calculate the appropriate air-fuel mixture: speed density and mass airflow.
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Fuel-injected systems are more complex and costly to maintain
In a common-rail system, fuel from the fuel tank is supplied to a common header (or accumulator) and then sent through tubing to the injectors, which inject it into the combustion chambers. The accumulator has a high-pressure relief valve to maintain pressure and return excess fuel to the fuel tank. The nozzle is opened and closed with a solenoid-operated needle valve. The common-rail injection is a variety of direct injection, which is one of the two main functional principles of mixture formation systems for internal combustion engines. The other is external, which is called a manifold injection system.
The fundamental functions of a fuel injection system are performed by a single component or multiple components. Fuel injection is operated by spraying pressurised fuel into the engine, which requires a device to pressurise the fuel, such as a fuel pump. Since the 1980s, electronic systems have been used to control the metering of fuel. More recent systems use an electronic engine control unit (ECU) which meters the fuel and controls the ignition timing and various other engine functions.
The primary means of getting gasoline into the engine cylinder so it can combust and the car can be driven is through fuel injectors. Fuel injection has been around since the 1950s and has been used widely in European cars since 1980. In the United States, the 1990 Subaru Justy was the last car sold with a carburetor; the following model year, the Justy had a fuel injector. Now, all cars sold in the United States have fuel injection systems.
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Electronic fuel-injection (EFI) systems are more precise when it comes to producing air-fuel ratios
Electronic Fuel Injection (EFI) is a modern technology used in the latest vehicles, which replaces the carburetor systems used in older vehicles. EFI is a fuel injection system with electronic control that observes the condition of the engine and determines the capacity of fuel that must enter the combustion chamber. This is achieved by sending a signal to the ECU, which is responsible for controlling all the activities of the car's combustion chamber components. The ECU, or Engine Control Unit, is the brain of the system, and the more sensors it receives, the more efficient the EFI system is.
The ECU is equipped with five sensors that detect each component's performance and play a role in determining the injector's opening and closing periods. These sensors are of five types: MAF, IAT, TPS, CKP, and MAP. The sensors provide voltage to the ECU, which allows for fuel processing. This system of electronic control is what makes EFI more precise when it comes to producing air-fuel ratios.
EFI provides an ideal mixture of air and fuel for the engine, which means the vehicle's engine will work more efficiently. This is because EFI can detect and adjust the air-fuel ratio in real-time, ensuring that the engine always has the optimal mixture for its current operating conditions. The result of this process is what the vehicle uses to run its engine and produce mechanical power.
EFI systems have several advantages over carburetor systems. They are more efficient, with faster engine response and the ability to run in any weather. EFI systems also have an automatic fuel cut, which stops fuel spray during deceleration. This contributes to better fuel economy and reduced emissions.
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EFI systems rely on the powertrain control module (PCM) to pulse the fuel injectors on and off
The Powertrain Control Module (PCM) is a digital computer that contains a microprocessor. It receives input signals from various switches and sensors, which it uses to adjust engine and vehicle operations through devices called engine computer outputs. The PCM is central to a vehicle's EFI system, which is the fuel system of choice for modern cars.
The PCM controls the fuel injectors by pulsing them on and off. It does not send power to the injectors; instead, power is provided by a fuse-controlled circuit from the ignition switch. The PCM grounds the injector, allowing it to inject fuel into the cylinder. It makes and breaks the ground several times per second to allow the correct amount of fuel into the cylinder. This process is called pulse width modulation, and it is measured in the percentage of duty cycle rather than voltage.
The PCM controls the fuel injectors in groups of four, with each pin supplying a signal to four fuel injectors simultaneously. This means that four cylinders are simultaneously in a power stroke and are injected with fuel at the same time. The distributor then fires these cylinders in sequence as they reach the top of their respective compression strokes.
The PCM also has a range of other functions, including full ignition control, transmission controls, traction control, and advanced OBD II diagnostics.
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Direct injection has fuel that goes to the cylinder heads
Direct injection is a fuel injection system that delivers fuel directly to the engine's cylinder heads or combustion chamber. This is in contrast to manifold injection systems, which inject fuel into the intake manifold.
Direct injection systems place a high-pressure injector directly into the cylinder head, allowing fuel to be injected with precision directly into the combustion chamber. This is distinct from indirect injection systems, where a pre-chamber or swirl chamber is used in conjunction with the primary combustion chamber.
The injector's spray pattern is designed to keep the fuel within the combustion chamber, with the edges of the piston's fuel bowl shaped to retain the fuel. This precision in the injection event, particularly the spray pattern, is critical in direct injection systems. Spraying fuel on the outer edge of the piston or cylinder wall can lead to reduced combustion temperatures and incomplete combustion.
Direct injection systems are usually more expensive and complex than manual fuel systems. However, they offer increased fuel efficiency, higher power output, and reduced emissions. The use of direct injection can also help avoid carbon build-up at low piston speeds by ensuring proper combustion.
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Frequently asked questions
Fuel injection systems rely on the engine computer to operate the fuel injectors. If your car has a carburetor, it will be entirely mechanical and rely on cables and vacuums to operate.
Mainstream cars began to feature fuel-injected systems in the 1970s due to their ability to decrease emissions.
Fuel injection is more precise when it comes to producing air-fuel ratios.
