Bosch Motronic Details Wanted

[Bruce Murray]

Folks,

I have been chasing down an intermittent problem on my ALFA 164 which uses
Motronic 4.2 system. The readings I have been taking show that the system
is nowhere as simple as the published literature indicates. I am wondering
if some one could explain the more subtle details of the working of these
units.

For example I have found that, using a Hall effect current sensor and
measuring the currents at various points in the circuit, the current
through the injectors shows, in addition to the expected variable duty
cycle, a lower current square wave at a constant frequency of about 100Hz.
Also the current through the idle speed regulator is not just quasi DC as I
would have expected, but contains a triangular waveform also at 100Hz.
Presumably this 100Hz is the bus timing.

I have searched high and low for info that explains in detail the operation
of the Motronic. I have read the manuals, and the Bosch books, but of
course they are directed toward people repairing cars and will not divulge
the interesting internal electronic design details.

I have also scoured the archives of this group to no real avail.

I must admit that fixing my car problem does not really require that I
understand the internals - it's just that I am intrigued.

Can anyone point me to this info, (SAE papers etc)?

Thanks

Bruce


Bruce S. Murray
Principal Engineer
BBN Technologies
a Verizon company
70 Fawcett Street
Cambridge, MA 02138
ph  617 873-3356
fax 617 873-2918
bmurray at bbn.com
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