Most of the 'points replacement' amplifiers such as the Mallory, Lumenition,
Crane, Pertronix, etc. extend the effective dwell so that the coil is being
charged longer. This is good for better high-RPM performance, and since the
electronic switches don't wear it's better from a maintenance point of view.
However, that longer dwell changes the profile of the current pulse that comes
through the little loop transformer on the back of the tach, and the OEM tach
circuit either triggers inconsistently or it won't work at all.
The replacement module bypasses all of the original electronics in the tach,
but it uses the original current loop transformer and the meter movement, so
it allows stock appearance and wiring to be used. To use it with the MSD,
Jacobs or other multi-spark boxes (or a crank-trigger system, for example),
you have to put in an extra wire, and you don't use the current loop
transformer.
Cheers,
Theo
From: michael king [mailto:michael.s.king@gmail.com]
Sent: May 18, 2010 5:14 PM
To: Smit, Theo
Cc: Joel Martin; Tigers@autox.team.net
Subject: Re: [Tigers] Ignition/Coil/Tach Setup
Out of ineterst do the crane control boxes suffer the same issues with the
tachs?
--
Regards
Michael King
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