Ign Advance on MR-2

[Joseph Obernberger]

"Diehl, Jeffrey" wrote:

> Hi all.
>
> I'm still learning, so be gentle... <grin>
>
> I've got an '87 MR-2 and I'm trying to figure out how it effects timing
> advancement.  It has 2 wheels in the distributor, one with 4 teeth, the
> other with 1.  The single-toothed wheel is probably used to run the tach and
> is slightly offset from the cooresponding tooth on the 4-tooth wheel.
>
> Now the teeth on the 4-tooth wheel pass by what looks like a magnetic pickup
> and I presume that this gives the ECM the baseline timing.  However, it also
> passes by what looks like a small magnet which is attached to the pickup.
>
> There are no vacuum lines, so it is not doing vacuum advance.  The only
> moving part is the shaft on which the two wheels move.
>
> So, my question is: How does this mechanism manage to advance the spark?
>
> Thanx for any input.
> Mike Diehl.
>

Not sure if your question has already been answered - but...The ECU controls
when the coil fires, and the ECU 'knows' the posistion of the engine.  So as far
as how it physically adjusts the timing:  The distributor is spinning around,
and the ECU knows where it is and how fast it's spinning...as the rotor
approaches the contact point (say spark plug wire 1), the ECU can fire the spark
sooner or later as the rotor wipes past that metal contact for wire 1.  Pretty
sure that is how it works anyway!

                                            joeo


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