Ign Advance on MR-2

[Diehl, Jeffrey]

Well, I opened the ECU case up the other day.  It only had 5 IC's on the
entire board.  But, it had rows and rows of resisters and capacitors.  And a
few transisters thrown in to make it interesting.  It really did look like
an analog board.

Go figure.

BTW, I found the tech docs very interesting.  Thanx,

Mike Diehl.

-----Original Message-----
From: Joseph Obernberger
To: Diehl, Jeffrey
Cc: 'diy_efi at diy-efi.org '
Sent: 8/12/2001 6:12 PM
Subject: Re: Ign Advance on MR-2

You might want to check out some 'technical documents' on Toyotas:
<http://josepho.www4.50megs.com/mr2-pdfs.html> - particularly THEORY.PDF
- it
explains how the ignition system works on various Toyotas.  I put
together a
distributorless ignition for my 1991 MR2T, and it worked...but seemed
too
sensitive to temperature changes so I have removed it.
<http://josepho.www4.50megs.com/ignition_project.html>
<http://josepho.www4.50megs.com/cgi-bin/i/ignition.jpg>
<http://josepho.www4.50megs.com/cgi-bin/i/ign_box.jpg>

I would be *very* surprised if the ECU were all analog.
                                                        joeo


"Diehl, Jeffrey" wrote:

> I think you've communicated the main problem for me.  I need to
understand
> how the ECU "knows" the engine position.
>
> If the ECU were a digital computer, I could imagine a fast clock and a
> counter which was latched at the passing of each tooth in the 4-tooth
wheel.
> This count could be used to calculate RPM and the clock could be used
to
> trigger the firing of the next injector/sparkplug.  But the ECU in the
MR-2
> doesn't seem to be that sophistcated.  Looks to be a completely analog
> system!
>
> I guess this same algorithm could be done in analog...  Is that how it
> works?
>
> Thanx,
> Mike Diehl.
>


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