> My
> question revolves
> around the measurement of dwell angle when using a Crane
> electronic ignition
> system instead of points. This system apparently has an optical pick-up
> instead of a rotor and points. Anyway, the analyzer identifies the dwell
> angle as 30 degrees, which I believe is probably correct for a
> points system.
> What I don't know is if there is a consistent measurement between the
> electronic ignition and points system. This analyzer appears to be
> technology consistent with a 25 year old vehicle, so I am curious
> as to what,
> if anything, the dwell angle in this case means.
David, assuming you have the Crane XR700 (they do make other types), it does
function as a "points replacement". The optical pickup triggers a power
transistor that performs the same function as the points, ie 'closing' to
allow current to build up in the primary of the coil, then interrupting the
current to cause a high voltage 'kick-back' that causes the spark. 'Dwell'
is the amount of time the points are closed, expressed as the angle the
distributor shaft moves while they are closed. So, you are still measuring
the same thing.
Of course, with the Crane the dwell is set by the electronics, there is no
adjustment for it. The optimum value is likely not the same as with points
anyway (which ISTR have a spec of more like 35 degrees).
> Incidentally, the tach
> readings on my car and the meter are very close to the same, which also
> surprised me somewhat.
Well, either they're both wrong, or your mechanical tach is in good shape
<g>
Randall
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