Mike,
It is my understanding that the stock tach works by measuring (i.e. counting the
frequency of) the current pulses that go to the ignition coil, which is why the
coil positive wire does a loop through the little lug on the back of the tach.
In order to keep this working, whatever you hook up to that sense wire has to
draw enough current everytime the engine fires to trigger the 'counting' circuit
in the tach. Most electronic ignition 'tach' outputs provide a voltage pulse
(not current) and thus would not trigger the tach correctly.
I'm guessing a little here, but my feeling is that the capacitive discharge and
other types of ignition modules that somehow store energy locally might not
provide the correct current profile at the supply wire to trigger the tach
properly, even if you ran the supply wire through the sense loop on the tach. My
Tiger has the Mallory Unilite distributor with the coil wired in the
conventional fashion, and the tach seems to work (i.e. the needle moves up and
down in accordance with the engine noises), although I sometimes have doubts as
to its calibration.
Theo Smit
tsmit@novatel.ca
B382002705
> -----Original Message-----
> From: Mike Burd [SMTP:mikeburd@email.msn.com]
> Sent: Wednesday, April 07, 1999 8:07 AM
> To: Tiger Questions
> Subject: Tack Question
[] <snip>
> 1 person said the tack will work just fine if you hook it up to one of the
> leads from the module and not the coil. They were not sure which color lead.
> I am not really concerned about 100% accuracy but would like it working. Has
> anyone hooked it up to the module? If so what wire?
> Mike
>
>
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