Ameer Randolph
Fuel injection systems have been around since the 1930s and 1940s, with the first fuel-injected engines being used for passenger cars. These systems have revolutionised the efficiency and performance of internal combustion engines, injecting fuel directly into the combustion chamber rather than the intake manifold. This is in contrast to carburetted engines, which mix air and fuel before entering the intake manifold. Single-point injection, which replaces the carburettor with one or two fuel injector nozzles, was a relatively low-cost way for automakers to reduce exhaust emissions while improving driveability. More modern fuel injection systems can add 10 to 20 horsepower and are more precise, although they are also more expensive. Direct injection is more common in diesel engines but is starting to be used in gasoline engine designs, and can be used to influence how combustion occurs in the cylinders.
| Characteristics | Values |
|---|---|
| Type | Single-point, Multi-point, Sequential, Batched, Simultaneous, Cylinder-individual |
| Use | Compression-ignition engines (e.g. diesel engines), Spark-ignition engines (e.g. petrol engines) |
| Advantages | Better "driveability", Reduced emissions, Boosted fuel efficiency, Increased power output, Lower oil consumption |
| Disadvantages | More black carbon aerosol production than traditional port fuel injection engines |
| History | First used in the 1930s and 1940s, Widely used in European cars since around 1980 |
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What You'll Learn
- Fuel injection systems have been around since the 1950s, with single-point injection being the earliest and simplest type
- GDI engines inject fuel directly into the combustion chamber, increasing efficiency and power output
- Fuel injection systems can add 10-20 horsepower and reduce exhaust emissions
- Multi-point injection injects fuel into the intake ports, rather than at a central point
- Direct injection gives engineers control over how combustion occurs in the cylinders
Fuel injection systems have been around since the 1950s, with single-point injection being the earliest and simplest type
Fuel injection systems have been around since the 1950s, with the earliest systems using analogue electronics for the control system. The earliest type of fuel injection system is single-point injection, also known as throttle-body injection. This system replaces the carburettor with one or two fuel-injector nozzles in the throttle body, which is the throat of the engine's air intake manifold. Single-point injection was a relatively low-cost way for automakers to reduce exhaust emissions and improve "driveability" (easy starting, smooth running, no engine stuttering). This system was used extensively on American-made passenger cars and light trucks during 1980–1995 and in some European cars in the early and mid-1990s.
The next development in fuel injection systems was multi-point injection, also called port injection. This system uses multiple fuel injectors to inject fuel into the intake ports just upstream of each cylinder's intake valve. Multi-point injection systems are more precise than single-point systems and can better achieve the desired air-fuel ratio, improving all related aspects. Sequential fuel injection, also called sequential port fuel injection (SPFI) or timed injection, is a type of multi-port injection that triggers each injector nozzle independently, resulting in further efficiency and emissions improvements.
Direct injection is another type of fuel injection that injects fuel directly into the combustion chamber, rather than into the intake manifold. This system is more common in diesel engines but is starting to be used in gasoline engine designs as well. Direct injection gives engineers more control over how combustion occurs in the cylinders and can increase engine efficiency and power output while reducing exhaust emissions.
The Bosch K-Jetronic system, introduced in 1974, is an example of a continuous flow fuel injection system, where fuel flows at all times from the fuel injectors but at a variable flow rate. This system was used until the mid-1990s by various car manufacturers.
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GDI engines inject fuel directly into the combustion chamber, increasing efficiency and power output
Gasoline direct injection (GDI) engines, also known as petrol direct injection (PDI) engines, are a type of internal combustion engine that inject fuel directly into the combustion chamber. This is in contrast to traditional port fuel injection (PFI) engines, which inject fuel into the intake manifold before it enters the combustion chamber.
The use of GDI engines offers several advantages over PFI engines. Firstly, they increase engine efficiency and specific power output. This is achieved through the precise control of fuel injection timing and pressure, which optimizes combustion and emissions. GDI engines often employ advanced ignition systems to ensure reliable ignition of the air-fuel mixture, and this precise control of ignition timing further maximizes efficiency and minimizes emissions. Additionally, GDI engines can be combined with turbocharging and engine downsizing to further enhance fuel efficiency and performance. The integration of turbocharging and downsizing with GDI technology allows for higher specific power output while maintaining fuel efficiency.
Another advantage of GDI engines is their ability to reduce exhaust emissions. GDI engines produce lower levels of certain emissions, such as CO2, when compared to traditional PFI engines. However, it is important to note that GDI engines have been found to produce higher levels of other emissions, such as black carbon aerosols and particulate matter (PM), particularly during cold starts and high acceleration. To address this issue, efforts have been made to optimize injector placement, combustion chamber design, and engine control strategies to reduce PM formation.
The design of GDI engines also contributes to their increased efficiency. GDI fuel injectors are mounted directly to the engine's cylinder heads, delivering fuel directly into the combustion chamber. This direct injection allows for lower oil consumption compared to older methods, as oil is injected separately into the crankcase. Additionally, the combustion chamber in GDI engines is designed to facilitate efficient air-fuel mixing and combustion, utilizing optimized piston bowl shapes, strategic placement of the fuel injector, and careful positioning of the intake and exhaust valves.
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Fuel injection systems can add 10-20 horsepower and reduce exhaust emissions
Fuel injection systems have been used since the 1930s and 1940s, with mass-produced diesel engines for passenger cars like the Mercedes-Benz OM 138 being among the first fuel-injected engines for passenger use. In the 1950s, fuel injection was introduced in passenger car petrol engines and had largely replaced carburetors by the 1990s. Today, all cars sold in the United States have fuel injection systems.
Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. A fuel injector is an electronically controlled valve that is supplied with pressurized fuel by the fuel pump in a car. The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open, which is called the pulse width and is controlled by the engine control unit (ECU). The ECU uses input from a variety of sensors to adjust the air-to-fuel ratio in real-time, a process known as closed-loop control. This allows for very careful control of the air-to-fuel ratio, which is necessary for the effective functioning of catalytic converters, which were introduced to meet stricter emissions requirements.
Fuel injection systems can add 10-20 horsepower to an engine. The exact increase in horsepower depends on the engine. Fuel injection systems also reduce exhaust emissions. This is achieved by manipulating the injection strategy, including the injection timing and pressure. Retarding the fuel injection timing, for example, can reduce brake-specific fuel consumption (BSFC) and NOx emissions. Additionally, gasoline direct injection (GDI) engines, which inject fuel directly into the combustion chamber, are credited with boosting fuel efficiency and reducing CO2 emissions.
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Multi-point injection injects fuel into the intake ports, rather than at a central point
Multi-point injection, also known as port injection, is a type of fuel injection system that injects fuel into the intake ports just upstream of each cylinder's intake valve. This is in contrast to single-point injection, which injects fuel at a central point within an intake manifold. In a multi-point injected engine, each cylinder typically has its own fuel injector, installed in close proximity to the intake valve. This allows the fuel to be injected through the open intake valve into the cylinder. The main advantage of multi-point injection is that it meters fuel more precisely than single-point injection, achieving the desired air-fuel ratio and improving various aspects of engine performance.
The history of fuel injection systems goes back to the 1930s and 1940s, when mass-produced diesel engines for passenger cars, such as the Mercedes-Benz OM 138, became available. These were the first fuel-injected engines for passenger car use. By around 1943, engines like the Rolls-Royce Merlin and Wright R-3350 switched from traditional carburetors to fuel injection, using throttle body manifold injection. In the 1950s, fuel injection was introduced in passenger car petrol engines, gradually gaining prevalence until it largely replaced carburetors by the early 1990s.
The primary difference between carburetion and fuel injection is in how the fuel is mixed with the air. Carburetion relies on suction created by intake air accelerated through a Venturi tube to draw fuel into the airstream, while fuel injection atomizes the fuel through a small nozzle under high pressure. Fuel injection systems can be classified into two main types: internal and external mixture formation systems. External mixture formation systems, also known as manifold injection systems, can be further divided into multi-point (or port) injection and single-point (or throttle body) injection.
Single-point injection, also known as throttle-body injection, was a relatively low-cost way for automakers to reduce exhaust emissions and improve "driveability" compared to carburetted engines. However, it did not allow for the precise mixtures required for modern emission regulations and is now considered obsolete. Multi-point injection systems, on the other hand, have evolved to use electronically controlled intermittent injection, with each injector nozzle being triggered independently. This ensures that the fuel is injected in a timely manner, minimizing unburnt fuel and reducing emissions.
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Direct injection gives engineers control over how combustion occurs in the cylinders
Direct injection systems have revolutionised the efficiency and performance of internal combustion engines. This is achieved by injecting fuel directly into the combustion chamber, rather than into the intake manifold.
The air/fuel mixture is produced within the cylinder, with the "swirl" of the entering air mixing with the fuel to form a homogeneous mixture. This results in combustion with exhaust gas that maintains concentrations closer to the optimum for catalytic converter conversion efficiency.
Direct injection also allows for robust control of combustion timing, which is initiated via a spark plug. This is unlike compression-ignited LTC concepts. The spark plug must be placed in such a way that it is in the zone where the mixture is ignitable, which requires very low production tolerances.
Another benefit of direct injection is that it achieves crankcase lubrication by injecting oil into the crankcase, resulting in lower oil consumption than older methods.
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Frequently asked questions
Fuel injection is a system where fuel is injected into the combustion chamber of an internal combustion engine.
Carburetted engines mix air and fuel in the required ratio before letting it into the combustion chamber, using the engine's natural air suction. Fuel injection systems inject fuel directly into the combustion chamber, and the air-to-fuel ratio is adjusted in real-time by the engine control unit (ECU).
Fuel injection systems can increase engine efficiency, specific power output, and reduce exhaust emissions. They also provide better "driveability" (easy starting, smooth running, no engine stuttering) and can add 10 to 20 horsepower.
