testing injectors

[EK]

I personally have not tried to test injectors or know what the requirements
are for your specific injectors, but a injector needing 4 amps to drive it
would be a very low impedance injector 12/4=3A, and sustaining that much
power (3A * 12V=36W) in an injector without sufficient cooling may cook it
in a minute. One trick I have used in pneumatic valves ( which may be what
peak and hold injectors use - I am new to the details of injector driving)
is to use a large capacitor charged above the normal operating voltage to
deliver a burst of power to pull the value off the seat initially, and then
reducing the steady state voltage / current so heat and power are minimized.
The steady state current thru the injector required to keep it open may vary
with pressure and temperature, so you may have to play with that if you are
running high or normal operating pressures. You may be able to use a 9V
battery or other small battery in some type of setup like this. If you can
find the simple circuit that does something similar, I would sure use that
instead on the car battery option.


Eric

-----Original Message-----
From: James Weiler <james at brc.ubc.ca>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Tuesday, May 11, 1999 9:52 PM
Subject: testing injectors


>Gang, I was flipping through my copy of 'Maximum Boost' and noticed he
>had a simple injector tester.  He had the injector opened by a simple
>switch hooked up to a 9V battery and he said to measure flow for 1 minute.
>This would hold the injector open at 100% duty cycle.  I know this is a
>bad situation but for purposes of testing is this going to damage the
>injector (I don't need to measure for the whole minute, I could use 15-30
>seconds if that makes a difference).
>
>Will this work for peak and hold injectors?  If these injectors need 4
>amps to open then I'm going to need something like a car battery to open
>the injector.  Is using a car battery a bad idea here?  i.e 12V vs. 9V
>
>I have some professionally cleaned and flow tested injectors that I can
>use as a refrence and I'll use methanol or paint thinner as the solvent
>or hexane (I'm a biochemist so I can get anything) ya hexane sounds good
>as it's not too volatile, methanol would be cheaper and easier however.
>Need some thought here.
>
>I know someone posted a simple circuit to based on a 555 timer but I'd
>like to do this quick.  However if this is the only non destructive
>method then I will build that guizmo.
>
>Any and all ideas welcome as usual.
> jw
>