GM ECM injector driver capacity

[Sandy]

>Dunno what it crossreferences to, but the transistor that does
>the driving on my '7747 is labelled "M927". It (with the help
>of some other components like a LM1949, etc) was designed
>to drive a low impedance (1.5ohm?) peak-n-hold TBI injector.
>If your ECM uses the same transistor I'd *expect* you to be
>in good shape. 8 high impedance injectors in parallel would
>be about 2 ohms, no?  

Not a good idea, even though you can drive them from a current standpoing,
what about all that new back EMF. I am unsure what the affect on the
flyback diode will be. Might be ok, but I would guess not, again, if you
are going to take enough saturated injectors and parallel them togther, you
will cause the Peak and Hold driver to actually hit the peak, then fallback
to the hold current. So you now have a bunch of saturated injectors which
will be operating at 1/4 the required current. Even if you use less
injectors the LM1949 (maybe others) will roll the current back after some
time constant to the hold current so you might have a problem their too. 

Food for thought...


>
>Only the bench knows for sure.
>
>BTW--the voltage pike caused by the collapse of the injector
>current/field is handled by a 50v zener diode. As best as I
>can tell the '7747 driver circuit is implemented EXACTLY as in
>the LM1949 spec sheet...LM1949, resistor, zener, and a transistor.
>
>-greg
>http://www.acesag.auburn.edu/~gparmer/efi
>