New to list, have a question.

[cloud at peaches.ph.utexas.edu]

At 10:46 AM 3/5/99 -0600, you wrote:
>Hi everyone,
>I'm Eric Comstock and I just joined this list.
>
>I thought I would start by asking a question.  First my situation.
>
>I am working on a Chevy 350 using a Holley Projection4 TBI.  This is one of
>the origional analog units that used the MSD controller.  I also have the
>closed loop kit (O2 only) installed. So it gets inputs from the throttle
>position sensor, the distributor(RPM), the starter, coolent temperature,
>and the O2 sensor.  I installed a shut-off switch on the Closed loop kit,
>so that baseline adjustments can be easily made.
>
>The closed loop kit intercepts the TPS voltage and adjusts it in order to
>fool the computer into adjusting the fuel flow.
>
>OK, everything worked fairly well until I installed a RAM-AIR system on the
>car.  Now the difference between high speed on a cold night and low speeds
>on a hot day is too much for the system to cope with.


Eric,  I also have an early ProJection  ....  doesn't have the EGO
feedback though.  This is probably not going to be any real help
to you, but I thought I'd share some quick thoughts with you

  . the projection is an alpha-n controller -- only uses rpm and
tps to determine fuel flow

  . the temp input is, as best as I can determine, basically an
on-off kind of thing to enrich the mixture and energize the throttle
kicker, so I don't consider it a bona fide "input" for normal
operation

  . the "ego feedback" unit is only to keep the system closer to
stoic ......  a problem I constantly have is the unit always runs
rich .... it can be adjusted leaner, but then it will run entirely
too lean at certain points (I have a DPM watching an EGO, so I
get a little "feedback" myself  ;-)

... if you agree with the above (that the ego feeback is to try to
keep the unit from running so rich, and maybe to prevent the operating
points where it also runs too lean, and that it's not to really improve
on the operating characteristics of the unit ....)

  . then, consider that a MAP input might be more logical ??   I had
entertained the idea of either building my own ego feedback unit or
a map feedback unit -- or could actually sum the two together ??  All
that's needed is to sum the input from the tps with the conditioned
voltage(s) from the other devices.  To me, the map input makes more
sense and would elevate the unit from the status of simple alpha-n
controller to a simple speed-density unit (which their literature
claims it is anyway!).

Why haven't I done that?  The Bronco it's in is my "fun" truck and
doesn't get driven often and it has other needs first.  Second, I
am now collecting parts to put the oem ford maf setup on it.  This
will cost $1000 or more by the time I'm done, but it should work
without hiccups and I don't think any bandaid fix is ever going to
really fix the projection (not even their digital unit).

just some rambling thoughts on the ProJection ......

Tom Cloud <cloud at peaches.ph.utexas.edu>