[urq] urg computer question

[Steve Eiche]

Steve,
Practical?  Not a chance, but I don't think that is would any worse than building new replacement boards.  Personally, I think that would be a waste of time.  With all of the conversions going on out there, there are a lot of spare MAC-02s floating around.  For damaged ECUs, the only thing that keeps them from being repairable is when one of the proprietary NLA or NWA (Never Were commonly Available) parts fails. I really don't see any reason to make a replacement using 20 year old technology for use in some fraction of the 500 cars that could possible use it.  Honestly, it would likely be cheaper to buy Audi's remaining stock, if they have any, when you factor in development costs.

What does make some sense, to me anyway, is to come up with some circuitry fixes to integrate into existing ECUs to correct the original design flaws.  The MAP sensor is easy, there are several fixes for that using Bosch or Motorola (Freescale or whatever they call themselves these days) parts.  The intake air sensor fix should only take a couple of component value changes.  The frequency valve circuit only needs a good replacement for the 2SD1087.  The EPROM just needs a small adapter PCB to use a more modern part.

Now, if I won the lottery and got _really_ bored, I think that a new replacement ECU that would plug in would be pretty easy to make.  Forget the existing circuitry.  Just look at what the inputs and outputs are, along with the map information for timing, boost, temperature, etc., which is all documented, and design the circuit around it.   There are now processors with all of the timers, A-D, PWM and even RAM and ROM that would be needed to duplicate the old ECU with a minimum of external components in a board less than a quarter the size of the original.  You could also add some diagnostics, which I find very desirable these days. :) If anyone is looking to do this, I'd be happy to give some design input and component selection ideas, but unless I hit the lotto (not likely since I never buy tickets) I don't see myself ever having the time or desire to do it myself.

Steve 

Steve B. wrote:
>  ... is this option truly practical?  At what level would you do the
>  redesign?  It would be difficult to implement a processor that executed
>  the same binary code as the MAC-02.  The schematic only gives so much
>  ... there is that proprietary Hitachi chip in there too ... do we have
>  an user's guide for that device?  Since this is Steve E talking there
>  must be some reasonable chance this would be doable ... but it seems
>  somewhat time consuming ... wouldn't there be more upside in working on
>  something that would allow a switch to EFI?  
>
>  I was also intrigued to read Tony's note about Doc Keene's car ... he
>  actually managed to convince a smog tester that his car was correct? ...
>  or did he get it approved by a referee?  If there was some chance that
>  this is a possibility, one which would not raise the worry of finding a
>  smog shop to do the inspections every other year ... I've got to say
>  that is the way I'd really want to go for myself ... 
>
>  Steve

>> 
>> I know where you are going with this, but personally I think 
>> that the best solution would be to make a replacement PCA 
>> that could run improved code with modern components.  I don't 
>> see any reason to duplicate what is a poor design to begin 
>> with.  While I was at it, I would fix design issues like the 
>> stupid low resistance intake air temp sensor and replace the 
>> MAP sensor with a modern Motorola part, etc.  You might as 
>> well add some rudimentary diagnostics and external 
>> programming while you are at it. Maybe that is what you have 
>> in mind.  I do believe that the main connector is still 
>> available from AMP.  
>  
>