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What's the Difference between Low and High-Impedance Fuel Injectors?

Posted by Wes Broadhurst on
What's the Difference between Low and High-Impedance Fuel Injectors?

In order to understand the difference between low and high-impedance fuel injectors, it is first important to understand what impedance is. Impedance is a measure of opposition to the flow of an electrical current. In other words, it is a measure of how much a material resists the flow of electricity. The higher the impedance, the more the material resists the flow of electricity.


In general, low-impedance fuel injectors are better for high-performance applications where a large amount of fuel is needed, while high-impedance fuel injectors are better for more moderate applications where a smaller amount of fuel is sufficient. But with the growing popularity and use of high impedance fuel injectors, the gap between the two is getting smaller and smaller.


Let’s dive into the technical and functional differences between low and high-impedance injectors:


What Makes Up Injector Impedance?

At its core, injector impedance measures the degree of ease with which a circuit processes the current when a direct voltage runs across it. It is vital to understand that you measure impedance in ohms. Impedance shows a direct correlation between introduced and processed voltage at the endpoint. 


In addition, understand that injector impedance boils down to a wide range of elements. Predominantly, impedance depends on electricity qualities like inductance, reactance, capacitance, and resistance. The majority of injectors divide into low and high-impedance.


High Impedance and Low Impedance Fuel Injectors

Typically, high impedance injectors have a coil resistance from 8-16ohms. In fact, this range of high impedance injectors is more widely used than any other injector. And that’s because the drive circuitry of high impedance injectors is straightforward and utilizes a saturated driver circuit.


Unlike high impedance saturated injectors, low impedance injectors have different mechanics. For starters, low impedance injectors have a coil resistance of 4 ohms or lower. Ordinarily, these ranges of low-impedance injectors align with high-performance or large-sized injectors.


For these types of injectors, driver circuitry is referred to as a peak-and-hold system. It is a more expensive and complex type of injector than the widely used saturated driver circuit. In a traditional peak-and-hold system – the main driver enables a time-sensitive and high current to turn the low-impedance in an instant.


Subsequently, the current is reduced to a lower value to ensure the injector is open. On average, it takes peak-and-hold current to hit 4 amps to open up the injector. Once it is open, the current can decrease to 0.75 amps.


If the coil resistance is lower, the internal pressure that keeps the pintle close can increase to shut down the injector faster. Consequently, it allows users to leverage faster closing and opening times to make tuning large-sized injectors easier.


How to tell the difference between high-impedance of low-impedance injectors?

If you want to save your valuable time and resources, the last thing you want to do is get the wrong components. And when it comes to building a solid fuel system, opt for the best injectors. And that’s why understanding the differences between low and high-impedance injectors is crucial.Here’s the thing – low and high impedance injectors don’t have generalized visual parameters or indicators. Instead, you have to proactively measure the resistance between two separate electrical terminals of an injector.


In layman’s terms, the main difference between low and high impedance boils down to the coil. A low impedance injector has a resistance of 2-3 ohms throughout the injector coil. What’s more, is that you can measure this value with a standard ohm or volt meter.


On the other hand, high impedance injectors tie together with most street applications. High impedance injectors are used as saturated injectors as a highly cost-effective solution. With high impedance injectors, you can measure around 8-16ohms.


Low impedance injectors or peak-and-hold drivers involve high-pressure fuel pressure and a large injector, allowing more current to flow across the injector with utmost consistency. The circuit driver can regulate current from 4-10 amps to open the injector. Next, the circuit driver decreases the current flow to keep the injector open.


In short, it takes additional current to open the injector faster and decrease the current to ensure there is no excessive current load. The major downside of a peak and hold or high impedance injector is its high cost. Conversely, low impedance injectors are used in purpose-built applications.


How to choose between high-impedance and low-impedance injectors.

It is easier to determine the type of injector your car uses than you think. All it takes is to measure and review the impedance of OEM injectors and then select injectors that perfectly match your impedance. But failure to follow this basic rule means the risk of damaging your vehicle's ECU.


While several aftermarket ECUs can support low and high impedance injectors, you should select parts with proper documentation and verify their system support and added capabilities.


High impedance or saturated fuel injectors can send 11-12 amps current. A low amp lowers the injector's temperature, making it highly reliable. It is one of the main reasons high impedance injector design is more widely used for OEM applications.  


On the flip side, peak-and-hold or low impedance injectors send a more robust electrical signal that reaches 56 amps. But after the injector is open, the electrical signal can reduce to 23 amps. Although this type of design closes and opens quickly, it gets hotter in a short time. In layman’s terms, fuel injectors with a flow of current over 70 lb an hour are low impedance.


For the sake of context, the injector you need for a specific application can vary and depends on power levels and ECUs. For instance, if the high demand for fuel propels you to use low impedance injectors based on an ECU that was supposed to be used for high impedance, then you will have to run separate resistors to balance out the different current levels and demands. 


Low and High Impedance Injectors: Connectors and Body Style

Whether it’s EV1, EV6, or EV14 – they’re all standard injector styles set forth in motion by Bosch. In the automotive space, E1, EV6, and E14 body styles are the most common. Despite the popularity of Bosch products – it is not the exclusive manufacturer in the automotive industry. In fact, several other brands supply similar injectors in the automotive market. 


In any case, if you value performance and don’t want to deal with redundant components, opt for genuine products that can improve your vehicle’s engine. For instance, you can browse the performance line of SEP-branded components to get a lifetime warranty.


Typically, the body style is the direct indicator of the connector type an injector uses. For the most part, these connectors are OEM-specific. As far as connector styles go, your system either uses a modern square connector with narrow and rounded prongs or an older rectangular style connector with two flat prongs.


Low and High Impedance Injectors: Size and Flow Rates

It is hard to discuss high and low-impedance injectors without bringing size and flow rate into the picture. In layman’s terms, static flow refers to the maximum fluid amount an injector flows at an open operation. Contrary to misguided misconception, a bigger size does not mean it can support your specific situation. Instead, don’t choose a small or large fuel injector that might not meet your requirements. Depending on your needs, there are downsides to picking small and large injectors.  


For instance, extremely small injectors can trigger a lean engine condition. And when it comes to extremely large injectors, the operational functionality of the injector gets compromised due to non-linear range and oversizing.


High Impedance Fuel Injectors continue to dominate the market

Today, high impedance injectors are more in demand than low impedance injectors. In fact, the demand for high impedance injectors has increased tenfold in the last few years. When it comes to building high-z injectors, make sure the manufacturer provides an injector that matches specific flow and data and renders reliability and consistency like Snake Eater Performance¹.


Need help choosing the right parts for your vehicle?

Whether it’s fuel injectors, fuel pump filters or fittings, fuel pressure regulators, or fuel pumps, you can lean on the team at Snake Eater Performance to help you build your dream machine. Snake Eater's performance fuel injectors come with a lifetime warranty and customer service you just don’t find anymore. We’re here for you before and after the sale. Contact us today!


REFERENCES:

  • Clearing Up The Confusion In Modern Fuel Injector Technology - Kyle Kitchen - https://www.enginelabs.com/news/clearing-up-the-confusion-in-modern-fuel-injector-technology/ 

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