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From this Hot Rod article, I understand that low-impedance injectors run higher current and open and close faster than high-impedance equivalents. The heating effect of the higher current also results in hotter fuel.

Unless the engine revs to the moon (say 15K RPM) I don't see the benefit in swapping out high-impedance injectors for low-impedance ones. Why do people do this then on the engine mod scene? Is there something I'm missing here?

4

For the most part, I believe people put low impedance injectors in their vehicles because that's what everyone else does. They are just "keeping up with the Jones'" in the pseudo-high performance world. Most applications will not require them.

There are two reasons which might require a low impedance injector:

  • If the engine has to rev very high (as you mentioned)
  • If a high impedance injector will not flow enough fuel for your needs.

If your car doesn't need them for these purposes, you probably don't need them in your car. The down side to low impedance are two fold:

  • Since they have a higher amperage rate to utilize, they create more heat, which is transferred right into the fuel (since fuel is what cools injectors).
  • If your ECU is made for high impedance injectors, you have to run resistor packs in order for the injectors to work, which provides another fault location in your vehicle. NOTE: You can have new drivers installed on some ECUs to allow them to work with low impedance injectors. If your ECU is OEM, you'll most likely not be able to do this.
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I don't see much benefit in them either. When you install any after-market injectors, you update the ECU maps to accommodate the latency of the new injectors and never worry about it again. As long as they open and close fast enough so that you can get enough fuel into the cylinder prior to each combustion stroke, it doesn't matter what their latency is.

1

Perhaps with very clever mapping they can be pulsed as opposed to simple opened and closed leading to better atomization of fuel. Other than that, I can't see much clear advantage.

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