Rajan Wilcox
Fuel injection systems have been used in cars since the 1950s, and all cars sold in the United States have been required to have them since the 1990s. There are several types of fuel injection systems, including single-point, multi-point, direct, and indirect injection systems. The type of system used depends on the vehicle's engine and performance requirements. Fuel injection systems have evolved to become more efficient and eco-friendly, and modern systems are electronically controlled and use a wide array of data sent from various sensors to regulate the amount of fuel injected into the engine.
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What You'll Learn
Carburettors vs fuel injection
Fuel injection and carburettors are the two primary types of fuel delivery systems used in cars, motorcycles, planes, and other vehicles. The end goal of both systems is to mix the right proportions of air and fuel and send it to the cylinder, where it can be ignited by the spark plugs. However, there are several key differences between the two systems.
A carburettor is a device that physically mixes air and fuel in the required ratio before letting it into the combustion chamber. It is technically simple, inexpensive, and easy to maintain. It does not require electricity, instead relying on the engine's natural air suction. Carburettors use a Venturi Tube that narrows in a section, decreasing air pressure and creating a vacuum. This vacuum pulls fuel into the carburettor, and the ratio of air to fuel is adjusted using two valves: the choke and the throttle. The choke decreases the amount of air and increases the flow of fuel, causing the engine to run lean, which is useful during cold starts. The throttle valve, or butterfly valve, regulates how much of the air-fuel mixture flows into the engine. Opening the throttle valve wider allows more of the mixture to flow in, pushing the car to accelerate.
Fuel injection, on the other hand, atomizes the fuel through a small nozzle under high pressure, resulting in a more precise fuel control. The fuel injectors may spray fuel directly into the cylinders (direct injection) or into the manifold leading to each cylinder (indirect injection). The injectors are fed pressurised fuel by an electric fuel pump and an array of sensors and an electronic control unit to precisely meter out the amount of fuel being injected. This allows fuel injection systems to deliver the best mix of power and fuel economy and makes them more reliable, effective, and eco-friendly. They are also easier to diagnose, as an OBD2 scanner can be plugged in to query the computer system for errors.
Carburettors were the predominant fuel delivery system before the new era of microchips and complicated automotive electronics. However, starting in the 1980s, injector technology began to replace carburettors. Today, fuel injection systems have largely superseded carburettors in new automobiles, although carburettors are still in use in simpler engines for scooters, motorboats, chainsaws, or lawn mowers.
There are several advantages and disadvantages to each system. Carburettors are cheaper to buy and repair, and they are more tolerant of substandard fuel. They also do not require electricity to function. However, they are harder to tune to pass emissions regulations and are more prone to fuel and air leaks. They may also struggle in forced induction applications and at colder temperatures and higher altitudes without adjustment.
Fuel injection systems, on the other hand, provide better fuel economy, increased power at lower engine speeds, and improved overall stability. They are also more reliable and effective at starting in cold temperatures. However, they may be more expensive and complicated to set up, and they require electricity to function.
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Different types of fuel injection systems
Fuel injection systems are a combination of mechanical and electronic circuits that supply fuel to the engine. Over the last century, these systems have evolved considerably, from carburetors to single-point injectors to today's direct fuel injection systems.
There are two main functional principles of mixture formation systems for internal combustion engines: internal and external. A fuel injection system that uses external mixture formation is called a manifold injection system, which can be further divided into two types: multi-point (or port) and single-point (or throttle body) injection.
Single-point injection, also known as throttle body injection (TBI), is the oldest and simplest form of fuel injection. It uses one or two fuel injectors in the throttle body, which deliver the appropriate ratio of fuel-air mixture to each fuel intake manifold in the engine. The drawback of this system is that cylinders closest to the fuel injectors receive a better mixture than those farther away.
Multi-point injection, also known as port injection, injects fuel into the intake ports just upstream of each cylinder's intake valve, rather than at a central point within an intake manifold. This system allows for more even fuel distribution and is more efficient than TBI, resulting in enhanced fuel economy.
Internal mixture formation systems can be further categorized into several different varieties of direct and indirect injection. The most common type is the common-rail injection, a variety of direct injection. In a direct injection system, the fuel is injected directly into the combustion chamber or cylinder, resulting in no wastage of fuel or carbon deposit at the intake valve. Sensors monitor the exact amount of fuel needed and supply it to the chamber, making fuel metering more precise.
Another type of fuel injection system is the sequential fuel injection system, which is the most widely used today. In this system, the fuel injectors function in coordination with the cylinders they are connected to, injecting fuel only when the intake valve of the cylinder opens. This system saves maximum energy and improves emissions.
While direct injection was initially more common in diesel engines, it has increasingly been used in petrol engines as well.
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Advantages of fuel injection systems
Fuel injection systems have become increasingly common in cars since their introduction in the 1930s and 1950s for diesel and petrol engines, respectively. They have several advantages over carburetor motors, which they have largely replaced.
One of the main advantages of fuel injection systems is their accuracy and precision. Modern fuel injection systems are controlled electronically, allowing them to be much more accurate than carburetors. This accuracy enables them to comply with strict emission standards, as well as provide more power at lower engine speeds and increase overall stability.
Fuel injection systems are also more reliable and effective than carburetors. They are less likely to suffer from the issues that affect carburetors, such as providing inconsistent fuel-air mixtures to each cylinder. Fuel injection systems can deliver precise bursts of fuel to each cylinder, ensuring that each one receives the same mixture. This results in increased efficiency, power, and economy, as well as reduced emissions.
Another advantage of fuel injection systems is their ability to respond to sudden changes. For example, in sequential multi-port fuel injection, the system can respond quickly to sudden driver inputs, such as a sudden acceleration or deceleration. This is because the fuel injectors can open at the same time, or each one can open just before the intake valve for its cylinder opens, allowing for a quicker response.
Finally, fuel injection systems are more flexible in terms of engine design. Throttle body fuel injection systems, for instance, can be easily incorporated into existing engine designs as a replacement for carburetors. This allows automakers to avoid making drastic changes to their engine designs, saving on redesign and tooling costs.
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History of fuel injection systems
Fuel injection systems have been used in various combustion engines for over a century, although they only became commonplace in petrol engines relatively recently. The first fuel injection system resembling those used today was invented serendipitously in 1885 by British engineer Herbert Akroyd Stuart, who accidentally spilled a flask of kerosene into a pot of molten tin. Stuart noticed that while liquid kerosene was reluctant to ignite, its vapours burned eagerly. This discovery led to the construction of the hot-bulb engine, which entered production under licence in 1891.
In the early 20th century, fuel injection was used in aircraft design, with several German aircraft engines of the 1930s and 40s employing the technology. Mass-produced diesel engines for passenger cars, such as the Mercedes-Benz OM 138, also became available in the late 1930s and early 1940s, becoming the first fuel-injected engines for passenger car use. In 1940, Alfa Romeo experimented with fuel injection in the 1940 Mille Miglia road race, fitting six electronically controlled Caproni-Fuscaldo fuel injectors to a 2.5-litre engine.
In the 1950s, fuel injection began to appear in petrol engines, with the Goliath GP700 in 1952 becoming the first to feature the technology. In 1954, the Mercedes-Benz Formula 1 team fitted its "Silver Arrow" W196 racecar with Bosch direct injection, derived from the system used in the Messerschmitt Bf 109 fighter plane from World War II. This technology, along with other innovations, helped Juan Manuel Fangio and Stirling Moss win the championship in 1954 and 1955. In the US, Chevrolet introduced its 283 cubic inch "Small Block" V8, the first engine to feature Rochester fuel injectors next to the intake valves. In the same year, the British company Lucas developed its own variant of fuel injection, which was fitted to Jaguar racecars, resulting in a D-type winning the Le Mans.
By the 1970s, fuel injection was appearing in mainstream cars, and in the 1980s, it began to quickly overtake carburetors in auto design due to increased computing power and smaller EFI modules, which allowed for better control and more consistent performance. In the 1990s, direct injection was introduced as vehicles became more compact and engines became smaller and leaner, representing a leap forward in the use of the technology. Since the mid-1990s, it has been impossible to buy a new car without fuel injection in Europe, and today, all cars are fitted with electronically-controlled fuel injection.
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How fuel injection systems work
Fuel injection systems have evolved considerably over the past century. The first mass-produced fuel-injected engines for passenger cars were diesel engines, which became available in the late 1930s and early 1940s. In the early 1950s, fuel injection was introduced in passenger car petrol engines, and by the early 1990s, it had largely replaced carburetors. Today, all cars sold in the United States have fuel injection systems.
A fuel injector is an electronically controlled valve. It is supplied with pressurized fuel by the fuel pump in the car. When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel, creating a fine mist that can burn easily. The amount of fuel supplied to the engine is determined by how long the fuel injector stays open, known as the pulse width, which is controlled by the ECU (engine control unit). The fuel injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.
There are two main functional principles of mixture formation systems for internal combustion engines: internal and external. A fuel injection system that uses external mixture formation is called a manifold injection system, which mixes air and fuel outside the combustion chamber. The two types of manifold injection systems are multi-point (or port) and single-point (or throttle body) injection. Multi-point injection systems use multiple fuel injectors, while single-point injection uses one injector in a throttle body.
Internal mixture formation systems can be separated into several different varieties of direct and indirect injection. In a direct injection system, the fuel is injected directly into the main combustion chamber of each cylinder, and the air and fuel are mixed only inside the combustion chamber. This allows for more control over the engine and more precise fuel measurement. Common-rail injection is the most common system in modern automotive engines. In an indirect injection system, the fuel is injected into a pre-chamber, where it begins to combust before being drawn into the main combustion chamber.
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Frequently asked questions
Yes, all cars today are fitted with electronically-controlled fuel injection. Fuel injection systems have been mandatory in all new cars in Europe since the 1990s and in the US since the 2000s.
Fuel injection is the process of introducing fuel into an internal combustion engine. Fuel injectors spray fuel into the engine in a mist form, allowing for better combustion.
Fuel injection systems offer better fuel efficiency and performance. They are also more eco-friendly as they result in lower emissions.
