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beepbeep beepbeep is offline
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Join Date: Jun 2001
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Originally Posted by juicersr View Post
Thanks Goran, just missed your post while answering Don. I understand better what's going on and can ask the proper questions of my tuning guy. What are your thought about when to go to 'low impedance' injectors?
Well, as soon as you step up to 60+ lbs injectors, choice will be made for you automatically as you simply won't be able to find high-impedance injectors of that size any more.

Reason for almost all big injectors being low-Z is that the biger they get, the shorter time they have to stay open in order to maintain the idle. Hi-Z injectors open slowly, but that's usually not concern as long as opening times aren't too short. But when injector flows a lot, you are forced to very small opening times at idle. And if you try that with hi-Z injectors,they start to open unevenly at their margins and mess upp idle, emissions and driveability.

For those reasons, most big injectors are more or less forced to use low-Z coils which "yank" the spindle fast enough to provide precise metering at very short pulse durations.

It works like this: you open the injector with full 12V in the beginning (resulting in 6A of current on 2 ohm injector, then go down to 3V after certain period of time just to keep them open but not overheating them. (figures vary from injector to injector).

Fitting low-Z injector on EFI that cannot trigger them properly (peak & hold) will result in overheated/burnt output stage of EFI and/or overheated injectors.

16 ohm injector is typically triggered with 0.75A. 2 ohm injectors is triggered with 6A. That's a lot more current/power that goes trough injector, and that the reason why it opens so quickly. But it also demands more from EFI.

Thank you for your time,
Old 11-09-2008, 01:16 PM
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