Injector firing circuits

[Dale Ulan]

> The idea is to replace the elaborate carby system (one single barrel and
> one twin barrel plus levers vacuum acuators etc. etc) with efi.

Cool. I'm doing something similar to my Buick 350.
> 
> Essentially it's equivalent to an 8031 running at about 66 Mhz. I designed 

That's pretty good. I wish production ECMs had speed like that...

> The two injectors used in the falcon seem to be peak and hold types.
> Scoping up the ECU up reveals a 700-800 uS pulse at full battery volts 
> followed by a variable time current limited tail, with 50 volt spikes at
> the transitions.

Try the MC3484S4 TBI injector drivers. Data should be available from Motorola.

Also, National Semiconductor has such a beast that uses a bipolar transistor
and a sense resistor, but the Motorola chip is much nicer. You apply a TTL
level signal to it, and it takes care of constant-current control after
the 4A peak. The current is 1/4 of the peak current.
You put in an external (usually 35 or so) volt zener to absorb that spike.

The National Semi chp is the LM1949 Injector Drive Controller.