[urq] urg computer question

[Buchholz, Steven]

... yes, I do still have Bruce's ECU ... but I've also managed to
collect a couple others that might be better lent to the cause should we
want to do so ... Bruce's ECU is in pristine shape and I'd hate to risk
it ... 

That said ... AFAIK we have nowhere near a complete schematic for the
ECU.  The one that is out there also has some inaccuracies.  I have some
notes that go a bit further, but I don't think this is a practical
project on several levels ... many of the components on the board were
proprietary ... which means that they will not be available ... and
there are quite a few other parts on the board that have gone obsolete
over the past 20+ years.  This means that any plan to remanufacture the
PC boards would require removing parts from existing boards without
damaging them ... 

Here are a couple alternatives that might be better use of time ... some
could well benefit from PCB design expertise ... 

1) We know that the pressure transducers in the MAC-02 are subject to
failure and are NLA.  It would be cool to put together a replacement
module using one of the currently available surface mount transducers to
provide a replacement ... perhaps even with an upgrade.  For example, we
could whip up a board that would allow a current technology surface
mounted Freescale pressure transducer to work in a MAC-02.  Taking that
one step further ... we could use a PT which had a greater max pressure
than the stock part and accommodate for the change in readings by
scaling the timing maps in the EPROM.  

2) Those of us with WX motors know that the MAC-02 is particularly weak
in the circuit that drives the OXS Freq Valve, and the driver parts used
in the current circuit are difficult if not impossible to find.  It
should be possible to reverse engineer the circuit and make a small
replacement PC board to plug into the board.  

... there may well be other weak points of the MAC-02, but I think those
are the main ones ... perhaps Mr. Eiche can chime in here ... 

3) I've always felt that switching to a MAC-11 or MAC-14 might be a
worthwhile project ... the issues there are differences in the location
of the reference pin and what you do about knock sensor(s), but the
advantages are that the later ECUs seem to be a bit more robust ... and
you can plumb a WGFV into the boost control circuit ... 

On my bench in the garage I've got a halfway cobbled together engine
simulator (or stimulator) which would allow testing of the ECU without a
running engine ... all I need to do is to finish a couple circuits for
the simulated reference and speed sensor signals ... and then program
the FPGA ... that is what I was planning to use to test Bruce's ECU out
of the car ... it is kinda cool because the ECU plugs into a WX harness
(compliments of Rocky M) ... 

All that said, at some point you've got to wonder how much more
difficult it would be to swap everything out for an EFI system.  The
biggest negative from my POV is the whole deal with passing the
emissions testing ... 

Steve B
San Jose, CA (USA)
> 
> Steve B has my stock MAC02 from the '84. You are welcome to 
> use it as a
> live model if it would help. It does have a problem with one of the
> circuits, I'm sure Steve could fill you in on the status. I'm still
> using a barrowed MAC02 which needs to go back to its owner someday.
> Hence my interest in your project is rather keen.
> 
> Bruce 
> 
> -----Original Message-----
> From: a.j.gaidos at comcast.net [mailto:a.j.gaidos at comcast.net] 
> Sent: Tuesday, January 11, 2005 9:42 AM
> To: n-engelbert at terrans.net
> Cc: urq at audifans.com
> Subject: Re: [urq] urg computer question
> 
> One page schematic. I was expecting more. Now I need a parts list to
> source parts and a mechanical drawing for the board outline, keepout
> areas, mounting and tooling holes. Fixed components like connectors
> would be a must as well.
> 
> ... I suppose you all see where I'm going with this.
> 
> -------------- Original message -------------- 
> 
> > On Mark Chang's page, he's got a link to Robert Houk's 
> > schematics for the 
> > MAC02. http://www.audi-quattro.org/misc/rdh/index.html It's about 
> > halfway down the page in dxf and gif formats. Don't know about the
> > parts list and mech drawings though. 
> > 
> > 
> > > All, 
> > > 
> > > Does anyone have a schematic, parts list and mechancial drawing of
> > > the hitachi computer circuit board in our US spec cars? 
> > > 
> > > I'm a senior circuit board design engineer and I'm surrounded by
> > > some great EEs and component engineers. 
> > > 
> > > I would like to redesign this circuit board but I need the above 
> > > information. Thanks, 
> > > 
> > > Anton