Dwell Control

[Ward]

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
> 





_______________________________________________________
Get your free, private email at http://mail.excite.com/