Sylvie Willis
A fuel injector's current draw, measured in amps, depends on several factors, including the type of injector, the fuel pressure, and the impedance of the injector. Most injectors pull a relatively low amount of current, typically around 1 amp, but this can vary depending on the specific setup and conditions. For example, the current draw of a fuel injector can range from 0.5 to 5 amps or more, depending on whether it is a low or high impedance injector and the voltage of the system. Additionally, the peak current draw of a fuel injector may be higher than the average or holding current draw, with some injectors drawing up to 5 amps or more at peak levels. Understanding the current draw of fuel injectors is essential for proper wiring and to ensure the injector's long life.
Characteristics and Values of a Fuel Injector's Current Draw
| Characteristics | Values |
|---|---|
| Typical current draw | 1 amp (A) |
| Peak current draw | 2-5 A |
| Low impedance injector peak current draw | 4-5 A |
| High impedance injector peak current draw | 0.8-1 A |
| Injector coil draw | 5-15 A |
| Fuel pump draw | 4-8 A |
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What You'll Learn
Injector and coil amp draw
The current draw of a fuel injector is dependent on its impedance. Injectors with low resistance (2-4 ohms) require more current to open (4-5 amps), while those with high impedance (12-16 ohms) operate at lower currents (0.8-1 amp).
Ohm's Law, which states that current (in amps) equals voltage divided by resistance (in ohms), can be used to determine the current draw of an injector. For example, a 12-volt circuit with a 12-ohm injector will draw 1 amp of current.
Most injectors pull very little current, typically around 1 amp each. However, different types of injectors will pull different amounts of current, and fuel pressure can also have an effect. For instance, the 660's injector pulls less than 1 amp, around 0.8 amps, while the LS1 square coils have a maximum draw of around 5 amps.
Peak and Hold driver systems are commonly used with low-impedance injectors. These systems deliver a high opening current (peak) and then maintain the injector open with a lower current (hold). In this configuration, each driver typically services two injectors, providing 2 amps per injector and holding with 0.5 amps.
It is important to note that the average, rather than peak, current draw should be considered when designing a circuit. Additionally, the circuit should be fused for the current capacity of the smallest wire in it.
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Calculating current draw
The current draw of a fuel injector is dependent on several factors, and there are a few methods that can be used to calculate it. One of the most important factors is the impedance of the injector. Typically, fuel injectors have low impedance, ranging from 2 to 4 ohms. However, some injectors may have higher impedance, ranging from 12 to 16 ohms. The higher the impedance, the lower the current draw.
To calculate the current draw of a fuel injector, you can use Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R), or impedance (Z). Mathematically, this can be represented as I = V/R or I = V/Z. For example, if you have a fuel injector with a resistance of 12 ohms and it is connected to a 12-volt circuit, the current draw can be calculated as follows: I = 12V / 12 ohms = 1 amp.
Another factor that affects the current draw of a fuel injector is the type of driver circuit used. There are two common types of driver circuits: saturated driver circuits and peak and hold driver circuits. Saturated driver circuits typically use high-impedance injectors and operate at low current levels, usually between 0.8 and 1 amp. This helps to keep the circuitry cool and ensures a longer life for the components.
On the other hand, peak and hold driver circuits use low-impedance injectors and require more current to open the injector, typically between 4 and 5 amps. However, once the injector is opened, the current drops to a lower level, around 0.5 amps, to keep the injector open. This is because the circuit has a built-in switching mechanism that allows it to hold the injector open at a lower current.
It is also important to note that different types of injectors will pull different amounts of current. For example, older LS1 square coils may have a maximum current draw of around 5 amps, while other injectors may pull as little as 0.8 amps at idle. Additionally, the fuel pressure used can also affect the current draw.
To properly size the power wires for a fuel injector, you may need to consider the peak current, peak time, and hold current settings of your Engine Control Unit (ECU). Typically, the peak current may range from 2.5 to 4 amps for 1-2 milliseconds, after which the current drops to a lower hold current of 0.5 to 1 amp for the remaining time the injector is open.
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Injector drivers
The amount of current drawn by a fuel injector is measured in amps and is dependent on the injector's impedance. A fuel injector with higher impedance will draw less current, while those with lower impedance will draw more. For example, a fuel injector with 12 ohms of resistance in a 12V circuit will draw 1 amp of current. Similarly, an LS injector with 14 ohms of resistance will draw 1 amp at 14 volts.
FuelTech's Peak & Hold PRO Injector Driver is a notable example of an injector driver designed for low-impedance fuel injectors. It features eight channels and offers a range of motor protections in case of injector or connection failure. This injector driver can deliver between 2 and 12 amps of software-selected current per channel and includes an internal temperature sensor, fault diagnosis, and protection against high temperatures.
The PRO Injector Driver from FuelTech also allows for a higher initial current to rapidly open the injector, followed by a reduction in current to approximately one-quarter of the peak value. This feature helps minimise the injector's dead time, which is the duration between the injector being energised and it effectively spraying fuel.
It is worth noting that different types of injectors will draw varying amounts of current. For instance, older LS1 square coils may have a maximum current draw of around 5 amps, while other injectors may pull as little as 0.8 amps at idle. Additionally, the fuel pressure utilised can also influence the current draw of an injector.
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Impedance of injectors
The impedance of injectors is a crucial factor in determining the current draw of fuel injectors. Impedance is a measure of how much a material resists the flow of electricity. In the context of fuel injectors, impedance refers to the resistance of the coil within the injector. This resistance is measured in ohms, and it determines the amount of current, or amperage, that the injector can draw.
There are two types of impedance ratings for fuel injectors: high-impedance and low-impedance. High-impedance injectors typically have a coil resistance ranging from 8 to 16 ohms, with some sources stating a range of 10 to 14 ohms or even 10.9 to 16.8 ohms. These injectors are commonly used in street applications and are known for their cost-effectiveness. The drive circuitry of high-impedance injectors is straightforward, utilising a saturated driver circuit.
On the other hand, low-impedance injectors have a coil resistance of 4 ohms or lower, with some sources specifying a range of 2.3 to 4.5 ohms or even 2 to 3 ohms. These injectors are typically used in high-performance or large-sized injectors and are referred to as peak-and-hold drivers. They receive a more powerful electrical signal, allowing them to open and close quicker than high-impedance injectors. However, low-impedance injectors run hotter and are more expensive.
The impedance of an injector determines its current draw. By dividing the voltage by the impedance in ohms, you can calculate the current draw in amps. For example, a 12V circuit with an injector having 12 ohms of resistance will draw 1 amp of current (12 divided by 12). It's important to note that different types of injectors will pull different amounts of current, and factors like fuel pressure can also influence the current draw.
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Peak and Hold driver systems
The current drawn by a fuel injector is dependent on its impedance. Low-impedance injectors require more current to open (4-5 amps) compared to high-impedance injectors (0.8-1 amp).
The Peak and Hold PRO Injector Driver by FuelTech is an example of a Peak and Hold driver system. It can deliver 2 to 12 amps of software-selected current per channel and has several integrated motor protections in case of injector or connection failure. It features an internal temperature sensor and protection against high temperatures. The module is housed in an anodized aluminium and plastic case, and firmware updates are available through CAN bus communication.
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Frequently asked questions
A fuel injector's current draw depends on its type and the ECU setting. A high impedance injector has a continuous current draw of around 1 amp, while a low impedance injector may draw 2.5-4 amps at peak and 0.5-1 amp when open.
Peak current is the highest amount of current drawn by a fuel injector when it first opens.
To calculate the current draw of your fuel injector, you need to measure its resistance with a multimeter and then apply Ohm's law.
The current draw of a fuel injector depends on various factors such as the voltage applied, the injector's resistance, and whether it is high or low impedance.
A fuel injector's current draw is an important consideration in your vehicle's electrical system. It can impact the choice of wire gauge and the sizing of other components such as the ECU and resistor box.
