Rajan Wilcox
Choosing the right fuel injector size is critical for engine performance and tuning control. Fuel injectors come in various sizes and types, and the right one for your engine will depend on factors such as the fuel type (e.g. gasoline, ethanol, or alcohol), the engine's horsepower, and the injector's physical dimensions and electrical connections. There are also different injector body styles and flow rates to consider, and while there is no industry standard, modern fuel injector manufacturers have solutions that can bring top technology to nearly every vehicle.
| Characteristics | Values |
|---|---|
| Fuel Type | Gasoline, Ethanol, Race Gasses, Alcohol, MTBE, Oxygenators |
| Fuel Injector Flow Rate | 43 psi/3 bar (industry standard) |
| Fuel Injector Sizing | Depends on horsepower, fuel type, and application |
| Fuel Injector Body Style | 34mm, 48mm, 60mm |
| Fuel Injector Calculator | FuelTech, Snake Eater Performance, Evans Tuning |
| Fuel Injector Control | Peak & Hold driver box, ECU |
| Fuel Injector Data | Injector Dynamics |
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What You'll Learn
Fuel injector sizing is critical for performance and tuning control
There are several factors to consider when choosing the right size of fuel injector. Firstly, the type of fuel used is important. For example, ethanol requires approximately 30% more fuel than gasoline to produce the same amount of power. This means that the injector size needs to be at least 30% larger for ethanol-based fuels. Similarly, the desired horsepower level will also impact the required injector size. A simple rule of thumb is to have 1cc/min flow for each horsepower. So, for a 1000 horsepower engine using a fuel pressure of 43 psi, a 1000cc injector is needed.
The physical dimensions of the injector, including its electrical connections, are also crucial. There are three common electrical connectors, and it is important to ensure that the chosen injector has the correct connectors. Additionally, the injector's body style or external dimensions should be considered. Most modern injectors fall into one of three sizes: 34mm, 48mm, or 60mm.
Accurate injector data provided by the manufacturer is essential for proper tuning and performance. This data includes information such as the dead time, which refers to the time it takes for the injector to open and fuel to flow once it receives a signal from the onboard computer.
Ultimately, choosing the right fuel injector size is a complex process that requires careful consideration of various factors. It is important to ensure that the injector is properly sized to achieve optimal performance, efficiency, and control.
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The type of fuel used will impact injector size
The physical dimensions and electrical connections of the injector must also be considered when selecting the appropriate injector size for a specific fuel type. There are three common electrical connectors that are not interchangeable, so it is important to ensure that the chosen injector has the correct connectors.
Additionally, the fuel pressure will impact the fuel flow rate. Higher fuel pressure will increase the flow rate, while lower pressure will reduce it. This can be calculated using a simple formula. For example, an increase in fuel pressure from 43 psi to 58 psi will increase the flow rate of a 42 lb/hr injector to approximately 48 lb/hr.
The impedance of the injector is another important factor to consider when selecting the appropriate injector size for a specific fuel type. High impedance injectors, commonly used in street applications, have a resistance value of around 12 ohms and a continuous current draw of around 1 amp. This design reduces heat buildup, allowing for extended operation. Low impedance injectors, on the other hand, require a peak-and-hold injector driver, which is more expensive and typically found in aftermarket ECUs.
It is also worth noting that the injector size will depend on the engine's airflow. To maintain the same air-fuel ratio (AFR), the fuel delivery rate must be doubled if the airflow is doubled. This relationship between airflow and fuel delivery can be understood by considering the brake specific fuel consumption (BSFC), which is a measure of the engine's efficiency in terms of fuel consumption relative to horsepower.
In summary, when choosing a fuel injector, it is important to consider the fuel type, physical dimensions, electrical connections, fuel pressure, impedance, and the engine's airflow characteristics to ensure optimal performance and efficiency.
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$13.49 $16.99
Injector body styles come in three main sizes
The first of the three main sizes is the Bosch style multi-point injector, which was first introduced in the mid-1980s for GM TPI engines. These injectors are the largest and tallest of the GM injectors. They are becoming less popular because they cannot deliver the high flow rates demanded by today's powerful engines. Bosch injectors used a connector that was known by three different names: Jetronic, Minitimer, and EV1. The Jetronic connector is the oldest, while the Minitimer evolved into the EV1.
The second size is the tall LS1 style injector, which is slightly shorter than the older Bosch TPI injectors and uses the EV1 electrical connector. The third size is the latest Gen IV style injector, also known as the LS3 style. It is the shortest of the GM injectors, and the first-generation LS1 injector is the next in line in terms of height. This injector is much slimmer and slightly shorter than the early Bosch injectors, taking up less space. While these early injectors were used in passenger car LS1 applications, they retained the EV1 or Minitimer/Jetronic connector.
In addition to the physical size of the injector, other factors to consider when choosing a fuel injector size include the type of fuel, the target power level, and the electrical connections. For example, ethanol requires approximately 30% more fuel than gasoline to produce the same amount of heat, which means that an injector for E85 fuel would need to be at least 30% larger. It is also important to note that there are three popular electrical connectors that are not interchangeable, so the chosen injector should have the correct connectors for the existing wiring harness.
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High and low impedance injectors
When choosing a fuel injector size, it is important to consider the differences between high and low impedance injectors. Impedance is a measure of opposition to the flow of an electrical current, or how much a material resists the flow of electricity. The higher the impedance, the more the material resists the flow of electricity.
High impedance injectors are the most common selection for street applications. They have a resistance value of around 8-16 ohms, although some sources put this range at 10-14 ohms or 12 ohms. This results in a continuous current draw of around 1 amp, reducing heat buildup and allowing these injectors to run for extended periods with excellent reliability. They are also more cost-effective.
Low impedance injectors, on the other hand, have a coil resistance of 4 ohms or lower, with some sources stating a range of 2-3 ohms. They require a peak-and-hold injector driver, which is more expensive and typically only used in aftermarket ECUs. The peak-and-hold system allows for faster opening and closing times, making tuning large-sized injectors easier. Low impedance injectors can flow a lot more fuel than high impedance ones without causing as many problems with startup and idling. However, the extra current flowing through them causes more heat within the injector, and they require a driver to work properly.
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The importance of accurate injector data
Accurate injector data is crucial when selecting the right fuel injector size for your engine. Fuel injectors play a vital role in the performance and efficiency of your vehicle, and choosing the correct size ensures optimal performance, fuel economy, and emissions control.
Injector data provides a clear understanding of the injector's flow rate, offset, and voltage latency. The flow rate indicates how much fuel the injector can deliver, while the offset measures the delay in the opening and closing of the injector, ensuring equivalent fueling in each cylinder. Voltage latency information is also key, as it helps tuners verify that the correct commands are sent to the injectors, affecting their actuation and deactivation.
Accurate injector data allows for precise matching and scaling, ensuring that all injectors work harmoniously. This data is especially important when dealing with electronic fuel injection (EFI) systems, where the injector's performance directly impacts the engine's overall performance. By using tools like the Fuel Injector Calculator, enthusiasts can make more informed decisions about injector sizing, taking into account factors such as horsepower, induction type, and fuel type.
Additionally, accurate injector data is essential for proper maintenance and upkeep. By understanding the specific characteristics of the injectors, users can ensure they are providing clean fuel, using appropriate additives, and performing the necessary maintenance to extend the life of their injectors. This proactive approach can prevent costly repairs, improve fuel efficiency, and reduce emissions, ultimately enhancing the lifespan and performance of the vehicle.
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Frequently asked questions
Choosing the right size of fuel injector is critical for performance and tuning control. Just like a carburetor, bigger is not always better when it comes to fueling your engine.
You need to consider the fuel type you want to run (e.g. gasoline, ethanol, race gases, or fuel additives), the injector harness plug style, and the flow rate. You should also check that the manufacturer provides accurate injector data.
A simple rule of thumb for sizing an injector for gasoline is to use 1cc/min flow for each horsepower. For example, if you want to make 1000 crank horsepower on 93 octane gasoline, using a fuel pressure of 43 psi, you need a 1000cc injector. For ethanol-based fuels like E85, remember to add 30% since ethanol requires more fuel to make the same power. You can also use an online calculator or estimate your brake specific fuel consumption (BSFC) to determine the right size.
Modern fuel injectors mostly come in three sizes: 34mm, 48mm, or 60mm.
