Date:         Sun, 14 May 2000 12:35:26 -0400
Reply-To:     David Beierl <dbeierl@IBM.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@IBM.NET>
Subject:      Re: dwell
Comments: To: Tom and Dana Cates <dcates1@home.com>
In-Reply-To:  <019f01bfbdbe$6ef13280$93f20a18@ashvil1.nc.home.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 12:06 5/14/2000, Tom and Dana Cates wrote:
>But there is no control module. Just a Pertronix, a coil and the stock dist,

The Pertronix module contains circuitry that detects the timing info from
the rotating magnet wheel, and other circuitry that emulates the action of
a set of points by generating (in what precise manner I can't tell you) an
output pulse that drives the coil secondary (that's the "control module" --
in this case it's internal to the Pertronix unit).  The simplest way would
be to simply use an internal capacitor and an electronic switch which would
operate precisely as a set of points, except with no physical wear, no
point bounce, and with pulse duration independent of rpm.  A possibly
better way would be to actively generate a shaped pulse.

Either way, the concept of "dwell" itself is somewhat meaningless.  Dwell
is the measure of the duration of point closure, measured in degrees of
distributor rotation.  This makes sense in a point-driven system where the
angular duration is constant but the time duration varies with rpm.  But in
an electronic system the time duration of the output pulse is either
constant or actively controlled, and the angular duration varies with rpm
-- so the "dwell angle" will be different for every engine speed.  Either
way, the people who built the electronics decided for you what the pulse
duration would be, and you can't change it.  I yam what I yam, as Popeye said.

Does that make more sense?

david
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"