GM ECM injector driver capacity

[Tom Sharpe]

I Think you are correct. The problem as I see it is the capacity of the
Darlington transistor. Ii have seen them in the TechAmerica catalog from .5 A to
75A (thats 450W). I am sure that the bean counters won't allow that much extra
capacity, but 2-5 times might be normal. Injectors are all peak and hold, so
tripping multiple ones might be a problem, but hold capacity should be plenty.
The flyback problem can easily be eliminated by doubling the diodes in the
circuit if the current one is too small.I can't do the math because my brother
is the EE.

Sandy wrote:

> I don't know about the nubers, but it relates to the heat dissipation of
> the flyback diode. Look at the LM1949 datasheet, it has some rough
> calculations for power dissipation of that. Like I said, might be fine, but
> you now have 9 times the current going back into that diode, and although
> the numbers seem low, I would imagine that it will more 9 times more heat
> as you are dumping much more back emf them one injector. The real question
> is, since they were peak and hold, and the impedance of the injector is
> much lower, thus drawing lots more current the EMF from that type of
> injector will be much higher, how much, I doubt 9 times, but might just
> work fine. The bigger problem _again_ is that if the injector is a peak and
> hold type, and it goes into hold mode will you be driving 10 injectors with
> 1/4 of their required current. 10 saturated injectors = 10 amps in parallel.
>
> Anyone that knows electronics jump in at any time ;-)
>
> Sandy
>
> At 12:03 PM 8/25/98 -0400, you wrote:
> >OK, I have one injector, and it is perfectly designed, and does the
> >following
> >
> >14.2 ohms
> >runs on 14.2 v
> >draws 1 A
> >
> >when turned off generates
> >300v
> >.001A
> >.001msec.
> >
> >When I hook up 9 more, wouldn't I expect to see, at turn off
> >300v
> >.01A
> >.001msec
> >
> >Why would more produce more voltage rather than current,
> >or anything more than more current?.
> >TIA
> >Bruce
> >