Regan Brown
Gas engines have fuel injectors, which are devices that atomize and inject fuel into an internal combustion engine. The use of fuel injectors in gas engines has become increasingly common in the 21st century, with many modern diesel engines also using a common-rail design. The first mass-produced petrol direct injection system for passenger cars was introduced in the 1997 Mitsubishi 6G74 V6 engine. Fuel injectors have been shown to improve engine speed, acceleration, fuel efficiency, and power while reducing emissions.
| Characteristics | Values |
|---|---|
| Fuel Injector Definition | A device for atomizing and injecting fuel into an internal combustion engine |
| Fuel Injector Function | Injectors deliver fuel under high pressure through a tiny nozzle or nozzles into the intake manifold or directly into the combustion chamber |
| Types of Fuel Injectors | Injection valves, unit injectors, mechanical fuel injectors, electronic fuel injectors |
| Fuel Injection Methods | Continuous injection, timed injection (pulsed injection) |
| Fuel Injection System | Direct injection, indirect injection |
| Fuel Injector Maintenance | Use an engine stethoscope to listen for irregular noises; check for fuel leaks; use a laser thermometer to check the temperature of the exhaust manifold |
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What You'll Learn
Injector types
Fuel injectors are electromechanical valves that spray pressurised fuel into an engine's cylinders. They are part of the fuel injection system used in internal combustion engines. The primary function of a fuel injector is to provide fuel to an internal combustion engine.
There are several types of fuel injectors, each with its own unique advantages and limitations. The four basic types of fuel injection systems are single-point fuel injection, multi-point fuel injection, sequential fuel injection, and direct injection.
In a single-point injection system, there is a common fuel injector for all the cylinders in the combustion chamber of the engine. This is the oldest and simplest form of the fuel injection system. It uses one or two fuel injector nozzles in the throttle body and is also called throttle body injection (TBI).
Multi-point fuel injection (MPFI) technology, on the other hand, provides each cylinder in the combustion chamber with its own injector at the front of their inlet valves (outside the intake port). This is why it is also called 'port injection'. Every injector sprays fuel simultaneously, and each cylinder receives a more precise volume of fuel, reducing the possibility of fuel condensation outside the intake manifold.
Sequential fuel injection is the most widely used fuel injection system today. In this system, the fuel injectors function in relation to the cylinders they are connected to. Each injector injects fuel only when the intake valve of the connected cylinder opens and remains idle otherwise. An ECU (electronic control unit) monitors the movement of the cylinders and triggers the injectors only when necessary.
Direct injection focuses on placing the injector inside the cylinder to directly inject the fuel, bypassing the intake valve or manifold. While this type of fuel injection system is usually seen in diesel engines, it is also used in petrol engines, where it is known as GDI (gasoline direct injection).
There are also different types of fuel injectors manufactured by companies like Toyota, Honda, Bosch, and Siemens. Some of these include unit injectors, common rail injectors, and hydraulically actuated injectors. Unit injectors integrate the pump and nozzle into a single unit, offering space efficiency but posing challenges in repair and maintenance. Common rail injectors operate with a high-pressure fuel rail to enable precise fuel delivery at accurate timings across multiple injectors. Hydraulically actuated injectors utilise hydraulic pressure to operate the nozzle and are cost-effective and simpler than electronic variants, but they may compromise precision.
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Injector failure
Gas engines do have fuel injectors. Fuel injectors deliver fuel into the engine's combustion chamber. They spray a fine mist of fuel at a precise angle, ensuring the engine has the right mix to ignite.
- Engine Stalling or Misfiring: The engine may stall or misfire due to an inadequate fuel supply to the cylinders, disrupting the combustion process. This can cause difficulty in starting the engine and a sudden decrease in performance, especially during acceleration.
- Erratic RPM Needle Movement: A faulty injector can send inconsistent amounts of fuel to the cylinders, causing unexpected fluctuations in engine speed. This will be visible as erratic movements of the RPM (Revolutions Per Minute) needle on the dashboard.
- Rough Idling: When a vehicle is idling, the engine speed should be smooth and steady. However, a faulty injector may cause a cylinder to receive too much or too little fuel, resulting in uneven engine speed and rough idling. This can be accompanied by unusual sounds, such as coughing or spluttering.
- Check Engine Light: The check engine light on the dashboard may illuminate, indicating a dirty or malfunctioning injector supplying an incorrect amount of fuel to the engine. This will lead to decreased engine performance and fuel economy.
- Bad Fuel Economy: A faulty injector may not deliver fuel efficiently, causing the engine to consume more fuel than necessary or struggle to utilize the fuel effectively. As a result, you may notice that you're filling up the gas tank more frequently despite no changes in your driving habits.
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Injection systems
Direct injection is a type of injection system where fuel is injected directly into the main combustion chamber of each cylinder. This system is commonly used in diesel engines and, increasingly, in petrol engines. The air and fuel mixture occurs only inside the combustion chamber, resulting in improved power, economy, and reduced emissions compared to indirect injection. Direct injection can be achieved through conventional helix-controlled injection pumps, unit injectors, or common-rail injection systems.
Common-rail injection systems supply fuel from the tank to a common header (accumulator) and then to the injectors, which inject it into the combustion chambers. The accumulator maintains pressure using a high-pressure relief valve and returns excess fuel to the tank. Common-rail systems include air-guided injection and spray-guided injection, with piezoelectric injectors enabling increased precision and higher fuel pressures.
The design and mounting of gasoline injectors vary, with some mounted in the intake manifold (multi-port injection or throttle body) and newer injectors mounted directly into the combustion chamber (GDI). GDI injectors use a multi-holed nozzle, while multi-port and throttle body injectors use a pointless-style nozzle. Gasoline injection pressures are generally lower than diesel injection pressures.
Modern engines have up to five injection events per combustion cycle, optimising efficiency and emissions reduction. Mechanical fuel injectors use springs and plungers to control fuel speed, quantity, timing, and pressure mechanically. In contrast, electronic control modules (ECM) in modern engines electronically control fuel quantity, pressure, and timing.
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Injection history
Fuel injection is the introduction of fuel into an internal combustion engine, usually a gas or automotive engine, via a fuel injector. The fuel injector sprays pressurised fuel into the engine through a nozzle under high pressure.
The first fuel-injected compression-ignition engine was constructed in 1902 and entered production in 1906. This engine was called the Antoinette 8V and was designed by the French inventor and aviation pioneer Léon Levavasseur. It was also the first production V8 engine in history. However, the first fuel injection system that resembled those of today was invented by British engineer Herbert Akroyd Stuart in 1885. Akroyd-Stuart's invention, the hot-bulb engine, entered production under licence in 1891.
In the early 20th century, most petrol engines used either a carburetor or indirect fuel injection. Carburetors mix fuel and air mechanically, while fuel injection uses electronic monitoring and calibration to precisely control the air-fuel mixture. The primary difference between the two is that fuel injection atomizes fuel through a small nozzle under high pressure, while carburetion relies on suction created by intake air. Carburetors were dominant in automotive design for a long time, and still held a large share of the market well after the introduction of fuel injection.
The concept of injecting gasoline directly into an engine's cylinders was invented by Swedish engineer Jonas Hesselman in 1925. The Hesselman engine burned petrol until it warmed up, then switched to a heavy fuel. Before being switched off, it had to be switched back to petrol to clean the system. This engine was used in buses and trucks from the late 1920s to the early 1940s by makers like Volvo and Scania. The Hesselman engine was the first direct-injected compression-ignition engine used in road vehicles, though its design was more similar to a petrol engine. Its main advantages were its ability to burn low-quality, cheaper fuels and its better fuel economy compared to similar petrol engines at the time.
During World War II, Germany began equipping some fighter aircraft with direct fuel injection to prevent engine stall-out during high-speed aerial maneuvers. In the early 1950s, fuel injection was introduced in passenger car petrol engines and gradually gained prevalence until it had largely replaced carburetors by the early 1990s. Direct injection was introduced in the 1990s as vehicles and engines became more compact, and represented a leap forward in technology. The increased computing power and smaller size of EFI modules in the 1980s also contributed to the success of fuel injection systems.
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Injection efficiency
Direct injection systems, commonly used in diesel engines and increasingly in petrol engines, have played a pivotal role in enhancing injection efficiency. In direct injection, fuel is sprayed directly into the combustion chamber under extremely high pressure, resulting in a more efficient technique compared to indirect fuel injection. This precision injection technology boosts power and economy while reducing emissions.
The evolution from carburettors to fuel injectors is a notable milestone in injection efficiency. Carburettors, which relied on suction to draw fuel into the engine, were inefficient and temperamental. On the other hand, fuel injectors atomise fuel through small nozzles under high pressure, ensuring a fine spray of fuel that enhances combustion and power output.
To further improve injection efficiency, manufacturers have introduced innovations such as higher-pressure injection systems and more advanced control algorithms. For example, the VW group adopted a 5-hole injector design, optimising combustion and power. Additionally, the introduction of electronic fuel injection (EFI) systems, such as the common-rail system, has provided more precise control over fuel delivery, contributing to increased efficiency and reduced emissions.
Maintenance and proper care of fuel injectors are also essential for maintaining injection efficiency. Regular cleaning of the fuel injection system, typically every 20,000 miles for electronic fuel injection systems, is necessary to prevent performance issues caused by dirty injectors. Monitoring the injector's ticking sound and exhaust temperatures are other ways to ensure optimal injector performance and identify potential issues.
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Frequently asked questions
Yes, all gas engines have fuel injectors. They are used to atomize and inject fuel into an internal combustion engine.
Fuel injectors are used to spray fuel into the engine's combustion chamber under high pressure. This is done either with a blast of air or hydraulically.
There are a few ways to identify a failing fuel injector. You can use an engine stethoscope to listen for irregular ticking sounds. You can also use a laser thermometer to check the temperature of the exhaust manifold. A failing injector will record a higher temperature of around 320deg C.
There are two main types of fuel injectors: mechanical and electronic. Mechanical injectors use springs and plungers to mechanically control the fuel speed, quantity, timing, and pressure. Electronic injectors, on the other hand, electronically control the fuel quantity, pressure, and timing.
