[Diy_efi] Low impedence injector flowbench and other flowbench Q's

Daniel Nicoson A6intruder
Thu Aug 24 12:52:04 UTC 2006


LM1949.  It is an IC chip that handles Peak & Hold injectors.  Go to the
Digi-Key web site, look up the LM1949, pull down its data sheet and you can
learn a lot about driving injectors.  Use a LM555 circuit like the rest are
telling you to provide your pulse train.

I actually run a secondary injector system on my Mustang, I used the LM1949
to control the big Darlington transistor for each injector.  This way I
could run both lo and high impedance injectors.  In the course of developing
that driver circuit I built the 555 based signal generator and have run up
to 4 hi impedance injectors at a time with it.  I don't think the Darlington
transistor I use would run 8 peak & hold injectors batch style.  Possibly
using a large Mosfet would allow that.  8 x 4 amps (that's your peak load
with 8 batch-fire P&H injectors).  Probably you could get by with 4
injectors at a time, compare results from two runs?

Anyway, pull down the data sheet, it will get you started.

Good luck,

Dan Nicoson

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of dustin allmaras
Sent: Wednesday, August 23, 2006 5:21 PM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] Low impedence injector flowbench and other flowbench Q's

Looking for some advice on building a flowbench. I've built a simple
injector flowbench that will comparison flow up to 8 high impedence
injectors. It's powered by a megasquirt ECU and stimulator.

I need to run both high impedence and low impedence injectors in the
flowbench and while I don't want to ask megasquirt questions here since
there's a website specifically for that, I'm leaning towards getting rid of
the MS and rigging up an OEM ecu or two that will run the flowbench. All I
really need is for a set of  injectors to pulse for simple comparison
flowtesting. I've been fumbling with the idea of using two different ECU's,
one for high impedence and one for peak and hold injectors and faking all
the required ECU inputs to get it to function well enough to fire injectors.
I'm familiar with the Ford EEC-IV computers and would probably use one for
the high impedence injectors, but I've never worked with anything peak and
hold before. I need to fire 8 injectors at the same rate, preferrably batch
and wondering if anybody could suggest an ECU that isn't too difficult to
work with that might handle the task for peak and hold injectors. I figured
the tach or engine position signal to the ecu would be the most difficult
and necessary input to reproduce without an engine, but I'm not against
spinning a distributor or cam sensor, etc with a small electric motor for
the time being. Could I fire low impedence injectors from an EEC-IV computer
with injector resistors?

Any thoughts on the issue would be most appreciated.

Another question is regarding firing a strobe or timing light to view
injector spray patterns. Anybody know a simple way to fire a strobe from an
injector pulse?

Finally, Anybody have an idea or known, simple solution for an inexpensive,
accurate adjustable (15-80 psi) fuel pressure regulator? I'm using mineral
spirits for a test fluid if it makes a difference.

Please help! Thanks for your time!

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