Injector timing

[garfield at pilgrimhouse.com]

On Thu, 21 May 1998 11:35:06 -0400, "Bruce Plecan" <nacelp at bright.net>
wrote:

>On a (ya, I get boring) gm ecm does it fire the injector in reference to
>the distributor (or DIS) incoming pulse, or the ignition timing pulse
>with the timing correction.

Oooo, now here's an oddity, a gm ecm question I believe I can answer for
the good doctor. (Wow, time to go for a lotto ticket!)

Anyhoo, on a timing diagram for a DIS TBI setup (the one I mentioned to
you on the phone awhile back, BP), it shows the injectors being fired
from the falling edge of the REF signal, which is NOT related to the IGN
timing at all. That (IGN) is timed off the rising edge of the REF
signal, as "base timing", and any added spark advance then move the IGN
point back in time toward the point where the injector is timed from
(distance between falling and rising edge of REF is 60deg-crank). If
words fail, see the picture below.

[For those curious about how this fact-anomaly could have occured, I
only know the above stuff cuz we use the DIS IGNs, dual'ed up for
redundancy, in our eXperimental Aviation stuff. And this usage was first
pioneered by another august flyboy member of this very DIY_EFI group,
whose initials are JAC. Thanks John!].

Gar

P.S. I have posted the 6-cyl DIS timing diagram to the ftp site. Figured
I'd nip requests for same in the bud. Dontcha just luv the internet!?
	ftp://efi332.eng.ohio-state.edu/incoming/DIS_6cyl.jpg
Enjoy!