555 EFI competition

[Greg Hermann]

>The 75-79 Cadillac EFI uses 8 port injectors with an open
>(no runners) manifold and throttle body.  It fires off one bank
>or the other from reed switches in the distributor.  The pulse
>width for the peak and hold injectors is essentially 1.8 ms
>plus a value directly proportional to absolute manifold
>pressure.  The MAP sensor is mounted inside the ECU with
>a long hose to the intake.  The pulse width is modulated by
>things like air & water temp, starting to cover start/cold
>
>The whole thing is done with OP AMP type analog circuits.  The
>basic fuel curve is a simple straight line of manifold absolute
>pressure vs pulse width.  For Wide Open Throttle a second
>richer line overrides the other.  I have reverse engineered the
>entire thing with detailed drawings of the circuit and explanations
>of how each section works (except that J-K Flip Flop).  This info
>is free to anybody by snail mail; I think someone has also
>scanned it for E transfer
>
>There is a mechanical switch on the throttle which feeds back
>21pulses as the throttle opens so the injectors can fire extra
>enrichment pulses.  It also indicates max or min throttle to the
>ECU.  There is not a variable resistor to feed back a voltage
>
>These units are fairly common in junk yard 76-79 Cad Sevilles
>and I have modified the pulse width for engines other than the
>stock 350.  But the possibilities are limited with a straight line
>fuel curve and no feedback loops.  Bruce Roe

The whole thing sounds a whole lot like Cad reverse engineered a Bosch
D-Jetronic.

Greg


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