Ameer Randolph
Fuel injection is the process of introducing fuel into an internal combustion engine, usually an automotive engine, via a fuel injector. The primary difference between carburetion and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while carburetion relies on suction created by intake air. Fuel injection systems have evolved over the years to keep up with emissions and fuel efficiency laws. The introduction of a secondary fuel injector is defined as the addition of extra fuel into the combustion chamber after the main injection. This is usually caused by residual pressure waves in the high-pressure pipeline connecting the pump and injector.
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What You'll Learn
- Secondary injectors can take advantage of the long column of air at high rpm
- Dual injectors can keep up with the needs of low and high rpm running
- Secondary injectors can be used to add fuel under boost
- Secondary injection in a diesel engine is the introduction of additional fuel after the main injection
- Dual injectors make CPU programming more critical
Secondary injectors can take advantage of the long column of air at high rpm
The introduction of fuel into an internal combustion engine is called fuel injection. All compression-ignition engines (e.g. diesel engines) and many spark-ignition engines (i.e. petrol engines) use fuel injection.
At high rpm, the engine draws in a long column of air. A secondary injector can take advantage of this long column of air. Atomization is the key factor here. Dual injectors can keep up with the demands of both low and high rpm running. Injecting fuel with an injector nozzle as far upstream of the intake port as possible allows the fuel to atomize while being tumbled in the natural turbulence of the intake tract. At 11,000 rpm, the engine gulps huge columns of air, and injecting the fuel upstream gives the gas a much better chance to create an even fuel/air mixture.
The upstream injector is also said to cool down the intake charge, making the mixture denser with oxygen, which translates into more power. This is how secondary injectors can take advantage of the long column of air at high rpm.
Dual injectors, such as those found in Kawasaki's KX250F, make CPU programming more critical. The two injectors must work together seamlessly to optimize fuel delivery. The secondary injector should only be activated when the engine rpm is high enough to utilize it. The extra time it takes for the upstream injector's fuel to reach the combustion chamber must be considered.
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Dual injectors can keep up with the needs of low and high rpm running
Dual injectors are a feature of electronic fuel injection, which uses a fuel pump to spray fuel into the intake tract in metered doses. This type of fuel injection does not rely on intake pressure. Kawasaki's dual-injector system, for example, has a primary and a secondary injector that work together to deliver the optimum amount of fuel based on rpm, throttle opening, and other sensor data.
The placement of the injectors is important. For example, one injector can be placed on the outside and one on the inside of the runner. However, this setup can be inefficient in practice. Having one injector close to the valve and one further away can work well, and if staged, can work even better. For instance, in the case of a high rpm motorcycle engine, it was found that running both injectors together below 5000 rpm resulted in a loss of power, but running the closer injector to the valve below 5000 rpm and then both after 5000 rpm resulted in increased power.
Dual injectors make CPU programming more critical, as the two injectors must blend seamlessly to optimize fuel delivery. The secondary injector needs to come into action when the engine rpm is high enough to utilize it. The extra time it takes for the upstream injector's fuel to reach the combustion chamber must be considered.
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Secondary injectors can be used to add fuel under boost
Dual-injector systems have a primary and a secondary injector that work together to deliver the optimum amount of fuel based on rpm, throttle opening, and other sensor data. At high rpm, when the engine is drawing in a large amount of air, a secondary injector can take advantage of the long column of air. The secondary injector comes into action when the engine rpm is high enough to utilize it. The extra time it takes for the upstream injector's fuel to reach the combustion chamber must be considered.
Dual injectors can keep up with the needs of low and high rpm running. Injecting fuel upstream gives the gas a much better chance to create an even fuel-air mixture. It is also claimed that the upstream injector cools down the intake charge to make the mixture denser with oxygen, which translates to more power.
The use of a second set of injectors to handle boost can be controlled by a piggyback ECU. However, this can lead to lean conditions and driveability problems at the transition points into and out of boost. This is because it can be difficult to predict how much fuel they will run in all situations.
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Secondary injection in a diesel engine is the introduction of additional fuel after the main injection
The purpose of the fuel injection system is to deliver fuel into the engine cylinders, while precisely controlling the injection timing, fuel atomization, and other parameters. The main types of injection systems include pump-line-nozzle, unit injector, and common rail. Modern injection systems reach very high injection pressures and utilize sophisticated electronic control methods. The performance of diesel engines is heavily influenced by their injection system design.
The fuel tank must be capable of storing enough fuel to operate the engine for a reasonable length of time. It must be closed to prevent contamination by foreign objects and vented to allow air to enter, replacing the fuel used by the engine. Diesel fuel lines can be heavyweight, medium-weight, or lightweight, depending on the pressure between the injection pump and the injectors. Diesel fuel must be filtered multiple times in most systems, with a typical system having three stages of progressive filters.
Diesel fuel injectors are arguably the most important fuel system component. They deliver a precise amount of atomized and pressurized fuel into each cylinder. Highly atomized, pressurized fuel distributed evenly throughout the cylinder results in increased power and fuel economy, decreased engine noise, and smoother operation. Modern diesel fuel injectors, such as those found in common rail fuel systems, use piezoelectricity for increased precision and can handle very high pressures.
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Dual injectors make CPU programming more critical
Dual injectors are a more advanced fuel injection system, which has become increasingly common in the 21st century. Fuel injection is the introduction of fuel into an internal combustion engine, most commonly automotive engines, by the means of a fuel injector.
Dual fuel injectors have been used on street bikes for years, with the Honda 2003 CBR600RR being the first bike to use the concept. The bike had a second set of "showerhead" injectors installed in the roof of the airbox. Dual injectors can keep up with the needs of low and high rpm running. At low rpm, the engine takes quick, little breaths and only uses a fraction of the air available. A single fuel-injector nozzle must be placed next to the intake port to deliver fuel at low rpm. However, at high rpm, when the engine is drawing in a large amount of air, a secondary injector can take advantage of the long column of air.
The use of dual injectors can also help to improve the atomization of fuel. Injecting the fuel upstream gives the gas a much better chance to create an even fuel/air mixture. It is also claimed that the upstream injector cools down the intake charge to make the mixture denser with oxygen, which translates into more power.
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Frequently asked questions
A secondary fuel injector is an additional injector that works with the primary injector to deliver the optimum amount of fuel based on rpm, throttle opening, and other sensor data.
Secondary injectors can help to improve the efficiency and performance of internal combustion engines by injecting fuel directly into the combustion chamber. This results in improved combustion efficiency and power output while reducing emissions.
A secondary injector is used when the engine rpm is high enough to utilize it. At high rpm, the engine draws in a long column of air, and a secondary injector can take advantage of this to deliver more fuel.
