Ign Advance on MR-2

[Rich M]

Mike, I've got a 4A-GE training manual at work (I think) which describes
this sort of stuff, I'll try and find it and scan relevant pages if it
helps.
Cheers
Rich
ps. if you don't hear, e-mail me to remind me!

> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Diehl, Jeffrey
> Sent: 12 August 2001 08:16
> To: 'diy_efi at diy-efi.org '
> Subject: RE: Ign Advance on MR-2
>
>
> For all fo you who have replied and tried to help me, Thank you.  I'm not
> trying to be difficult, but I have to really understand how this system
> works.
>
> My dad and I are considering an engine modification which will necessitate
> converting to a distributor-less ignition, or at least fooling
> the ECU into
> thinking it has a distributor....
>
> We're thinking that as the tooth approaches the magnet, it
> induces a current
> which gets larger as the tooth approaches and smaller as it
> passes, forming
> (perhapse) a sin wave pattern.
>
> Now, if the ECU fires a spark plug when this current exceeds a fixed
> voltage, we could advance/retard the ignition timing by adding a bias
> voltage into this equation.  The fact that the pickup only has two wires
> coming out of it implies that all of this math is being done
> inside the ECU
> and not by biasing the pickup itself, right?  These details are
> important to
> us when we try to build a circuit which emulates this behaviour.
>
> Any insight you may have would be most welcome.
>
> Thanx,
> Mike Diehl.
>
> -----Original Message-----
> From: Chris Conlon
> To: diy_efi at diy-efi.org
> Sent: 8/11/2001 12:46 PM
> Subject: Re: Ign Advance on MR-2
>
> At 12:42 AM 8/11/01 -0600, Diehl, Jeffrey wrote:
>
> >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.
>
> The tach should be run via a signal from the igniter. On an '87 it
> probably just takes a signal from the low voltage side of the coil.
>
> >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?
>
> That ECU uses an AFM. It doesn't measure MAP directly, but can figure
> out load, based on RPM and the AFM signal. It then uses the load value
> to adjust the spark timing. The ECU controls all aspects of spark
> timing... except dwell, which is probably controlled by the igniter.
>
> Actually that ECU is old enough that the Ne signal from the dizzy
> (the one with more teeth) may go to the igniter, which then feeds a
> copy of the signal to the ECU. (Operation is pretty similar to the
> other setup, though, from the ECU's point of view.) Just a quirk to
> watch out for when you're tracing down wires.
>
>    Chris C.
>
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