[Diy_efi] High-voltage P&H IDM

Adam Wade espresso_doppio
Wed Mar 1 02:24:18 UTC 2006

--- David Allen <davida1 at hiwaay.net> wrote:

> Has anyone made a stand-alone IDM that will take
> an injector pulse from a saturated-driver ECM, and
> create a peak and hold waveform?  I was thinking
> about making one that would operate high-impedance
> injectors (normally used saturated) in a peak and
> hold configuration.  The peak voltage would be 30V
> (or thereabout) and the holding duty cycle would be
> set to create the same current flow as the injector
> at 12VDC. This should improve opening time and
> result in a more linear low-pulsewidth map. I am
> thinking of this as a way to use big injectors on a
> small turbo engine without idle issues.

While there are single-chip solutions for running
either saturated with high-Z injectors or
peak-and-hold with low-Z injectors, I don't know of
anything commercially available to drive a high-Z
injector in a peak-and-hold mode, especially above
Vbatt (since most injector drivers seem to ground the
injector rather than switch the +12v side).

One disadvantage is that there is more moving mass and
a stiffer spring inside of a high-Z injector, meaning
that you'd have to create a much larger amount of heat
in the injector coil (and use more wattage) to open a
high-Z pintle injector as quickly as you could open a
low-Z disc injector using only Vbatt in a 12V system.

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