Dwell Control

[Bruce Plecan]

----- Original Message -----
From: Ward <wspoonemore at excite.com>
To: <gmecm at efi332.eng.ohio-state.edu>
Sent: Sunday, April 11, 1999 1:20 AM
Subject: Re: Dwell Control

Then why with the Haltech ecm ([E6GM] a direct replacement for the aussie
165) do they mention to use it with a ignition module that performs the
dwell controll?.
  Then why are there so many different ignition modules?.
How can the ecm perform a closed loop dwell controll with no feedback from
the coil?.
Bruce

> Bruce, the only time that dwell is controled by the module it when the
> system is in by-pass, (set init timing) or durring the 1st. part of start
> up, (when RPM lt 400).
>
> If you work it out, in usec it a tough job for an analog ckt. The math for
a
> V8 is sec = 15/RPM, this will be the time for a single cyl ecvent, or 90
> degrees of crank.
>
> Let use 3000 RPM. 15/3000 = 0.005 seconds or 5000 usec for 90 degrees of
> crank, if we have 20 degrees of spark advance, that say's we will fire the
> coil 20 degrees before the next Dist Ref Pulse, (DRP) or in fact, (90 -
20)
> or 70 degrees after the last DRP. each degree is 5000/90 or 55.5
> usec/degree.
>
> The interesting thing is that the coil is an electrical circuit and could
> care less about degrees of crank, but it tends to retarad (as in resist)
the
> flow of electrical current, and therefore requires time to charge up,(sort
> of like filing the bucket).
>
> So the dwell issue is an old hold over from point's. In fact the coild
don't
> care as long as you giveit enough time to charge, In the case of most GM
> coils the min time is about 1 500 usec.
>
> I am sure you will chatch on that I'm working this out as I go, I had a
> tough time when I ws desiging a computer ignition system abiout 10 years
> back, get the time travel issue under contol.
>
> As an aside thanks for the other info.
>
> Ward
>
>
>
>
>
> On Sat, 10 Apr 1999 10:01:25 -0400, Bruce Plecan wrote:
>
> > Well, I posted some time ago about the dwell control being in the
module,
> > and was corrected that it is actually in the ecm program.  Tada, well, I
> was
> > correct, as well as the correction.  In the DIS Teachers manual they
> mention
> > that the dwell control is in the module, and that it is a closed loop
> dwell
> > control.  Meaning if the module doesn't sense that the coil (s) were
> fully
> > charged, then the dwell was adjusted.  What the ecm must do is try to
> > account for this correction, hence it has what looks to be dwell control
> in
> > it.  Again all of the above, IMHO, and from the GM DIS Teacher's Manual.
> >    Bruce
> >
>
>
>
>
>
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