555 EFI competition

[bcroe at juno.com]

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

  

On Thu, 29 Jun 2000 20:56:53 -0700 garwillis at msn.com (Garfield Willis)
writes:
> On Thu, 29 Jun 2000 18:37:36 -0500, bcroe at juno.com wrote:
> 
> >Hey, If you can show me plans for EFI reduced to a 
> >555, I'll be the first to build it and withdraw the joke
> >Bruce Roe, With 79 Cadillac injection, ANALOG
> >ECU, and no OX sensor or closed loops at all
> 
> Does that Caddy use MAF or MAP or just TPS? :)
> 
> Gar
> 
> 
>
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