[urq] Need to Get a Specific Electronic Speed Signal From an UrQ Speedo......

[Steve Eiche]

Andrew,
So did you get the ECU issue worked out?  As for the speed signal, it needs to be characterized it first.  If it is just a discrete DC pulse, that would be easy.  If it is a CAN message, then it becomes MUCH more difficult.  I don't have the wiring diagrams working for the A8, so I can't tell if they use a discrete speed signal or CAN messaging.  If you know someone with access to AESIS, it would be pretty easy to find out.

If the signal is discrete, the best thing to do would be to check the signal and correlate it to the speed sensor signal.  The way to do that is to use two channels on an oscilloscope and compare (on an A8).  You may find that the speed sensor signal is a 12V pulse, and the speed signal sent to the ECU is just a "cleaned up" pseudo square wave signal of 0-5V with a pulse width that matches the speed sensor signal.  That would be pretty easy to do. Alternately, you could use an A8 cluster and see what the output is if you power it up, connect a speed sensor to it and spin it with the scope connected to those two signals.  That would likely be what I would do...    

I would assume that you want to use the analog ur quattro dash, not the digi, correct?  

Steve

Andrew wrote:

Does anyone know of a practical way to generate an A8 ECU speed signal from
the UrQ electronic (or cable) speedo sender? What I am wondering is if there
is a way to go back to the UrQ dash cluster from the A8 dash cluster
presently installed in my UrQ w/ 4.2L conversion. I'm not too versed in the
technical aspects, but it seems the A8 receives the same signal from the
transmission sender that an UrQ with a digidash does (same sender PNs) but
somewhere on the back of the A8 cluster that signal is modified and then
sent to the ECU. The need is to convert the signal coming from either the
cruise control sender or from an electronic sender into this A8 singnal...
then I can ditech the A8 cluster. Anyone have any suggestions, or know of
someone off-list who can help? I'm wondering if Mockry or Eiche can weigh in
on this....Thanks everyone.

Andrew Finney
1985 UrQ w/ V8.