DFI revisited

[Scot Sealander]

Orin wrote:

> > Just gotta find that post of Orins.
> > Was was sure it was on, then off when fired (coil part). I thought there 
> > was a .1sec disarm to it.
 
> Right, 0.1 sec after arming, they fire, like it or not.
> 
> That post is in the archives somewhere...

I saved a couple.... here is one of them.

Scot Sealander

======================================================================
  Subject: Re: Multi Coil Setups
     Date: Mon, 26 Jun 2000 12:38:52 -0700 (PDT)
     From: Orin <orin at diy-efi.org>
 Reply-To: diy_efi at diy-efi.org
       To: diy_efi at diy-efi.org


> >> Leaving them armed isn't safe at very low RPM.  They will fire after
> >> 1/10 second of being armed whether you tell them to fire or not.
> >> As I recall, over 2.7V on the fire input arms them, then
> >> grounding it fires them.
> 
> So not to worry, if THIS is the report you posted before, that's VERY
> valuable info all by it's lonesome, and I'm happy for it. I just
> wondered if there was MORE, being greedy an all. :)  I take it they're
> not smart enough to figure DWELL/saturation time from the previous
> series of firings, like an HEI module, so I was trying to ascertain just
> how much dwell compensation WOULD be required to operate them.

There is more.  I'll have to start digging.  It's more to do
with the exact voltage required to arm/fire them and,
the measured resistance of the fire input and the time you
need to ground it before the coil will fire.

I used a PIC circuit to gate a single coil ignition signal
to them and they ran fine - no misfire, plugs looked fine,
turbo car.  Now if I could work out why my circuit lost
sync with the cyl # at redline/the rev limiter (experiment
done on original ignition).

To see if they do any dwell compensation on their own,
I'd scope current draw against firing signal input.
I've used a TTL level signal generator to do this kind
of testing.  The coils do pull a few amps (from memory)
when you arm them... so it should be easy enough to see
if they pre-empt the signal.  I don't think they do since
I've seen some really weak sparks when playing with the
duty cycle on the signal generator.

Orin.

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