Looking at only one cyl it get a spark every TWO revolutions.  You can
do the rest.

inker man wrote:

>Hello Volks,
>
>I have a 1990 2100cc Digijet engine (European model). I want to
>measure engine RPM without a strobe light, by connecting a frequency
>counter to the Hall control unit ignition coil drive output.
>How is engine RPM related to ignition pulse frequency?
>The motor is a 4-stroke, 4-cylinder, where every cylinder gets a spark
>once in a complete revolution and no two cylinders are sparked
>concurrently (1-4-3-2 firing sequence as per Bentley), so it seems it
>should be a 1:4 relation. Can anyone verify or correct this
>conclusion?
>
>Also, looking at the schematic, I see that the coil driver output goes
>in parallel to the dashbord to drive the tachometer, but also to the
>main fusebox to two vacant relay positions (2 and 4).
>Can anyone verify this, and has anyone actually used this signal to add a tach?
>
>Cheers,
>Tman
>
>
>
>