High-impedance injector off a low-impedance driver?

Don Sauman donald at vianet.net.au
Wed Mar 13 20:50:56 GMT 2002


Hi from a new person to the list.

Things to consider:
Op amps normally require +ve and -ve rails
Slew rate 1.e. how fast the out tracks input may be a problem at some revs

Otherwise impedance conversion a good idea but look for a single rail device
like a transistor configure as an emitter follower.

Cheers
Don

"Geddes, Brian J" wrote:

> Okay, after a little research and lots of good advice from Bruce of the
> Megasquirt site, I've figured out that I can't run the two injector types in
> parallel.
>
> An EE friend of mine had the following idea:  what if I got an opamp, set it
> to a gain of 1 (I think that makes it a voltage follower?), and wired the
> inputs of the opamp in parallel with my low-impedance injector?  I could
> then use the opamp's output to drive the high impedance injector.  It seems
> like that should effectively recreate the ECU's injector driver signal for
> my additional high-impedance injector, but have it draw it's current
> directly from the battery/alternator.
>
> I'm no EE though.  Any problems with a system like this?  And where would I
> buy an opamp?
>
> Thanks,
> - Brian
>
> > -----Original Message-----
> > From: Geddes, Brian J [mailto:brian.j.geddes at intel.com]
> > Sent: Wednesday, March 06, 2002 10:25 AM
> > To: DIY EFI Mailing List (E-mail)
> > Subject: High-impedance injector off a low-impedance driver?
> >
> >
> > All -
> >
> > Hello!  I'm new to this list - I just stumbled across it
> > yesterday while
> > doing some research on fuel injectors.  As a newbie, of
> > course, I have a
> > question.  :)
> >
> > Is it possible to run a high-impedance (saturated) fuel injector off a
> > low-impedance (peak-and-hold) driver?  I have high-impedance
> > injectors in my
> > car (a '94 turbo mitsubishi), and would like to run a additional
> > high-impedance injector in parallel with one of my stock low-impedance
> > injectors.  What I've seen so far in my research makes me think it's
> > possible, but I'm not quite sure enough yet to try it.  Has
> > anyone done
> > something like this?  Would I need to stick a resistor in before the
> > high-impedance injector?
> >
> > Thanks,
> > - Brian Geddes
> >
> >
> >
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--
Don Sauman
Perth, Western Australia
"Life is short, live it now."


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