C/L WB/WOT OEM ECUs...

[Bob Tom]

At 07:55 PM 4/6/00 -0700, you wrote:
> <snip>
>Question is, if we want to use a wideband AFR sensor to control a simulated
>switch-type O2 sensor input to the ECU at any commanded AFR "crossing", then
>HOW do we go about using cal changes in the OEM ECU, and any other needed
tricks,
>to *contrain* the ECU to stay in closed-loop and follow the simulated O2
sensor
>input, to give us closed-loop control of AFR at any fueling regime we choose.
>
>I can see how one might use an EGOR-module (or NTK box, or whatever) to
>set a "commanded AFR", and also how to simulate this AFR as the
>"stoich-crossing" to the ECU that's expecting to see a switch-type O2
>sensor input, that's the easy part; what I don't fathom completely at
>this point is how to KEEP the normal OEM controller, even at significant
>TPS/MAP/MAF inputs, from leaving C/L, ignoring our O2 input, and running
>outta it's open-loop fueling tables, as it normally would. I'm thinking
>that anyone who shows how this trick can be done is going to make a
>major contribution to opening up WB WOT to wide application and
>experimentation, not to mention bringing the cost way down from the
>FelPro's and Motec's.
>
>Anyone wanna light the fuse, and get what's likely to prove a
>barn-burner of a thread going? I cain't help; I'm pretty clueless when
>it comes to the OEM ECU end of things.
>Gar

My particular interest is with the Dodge truck pcm.  Information is
sparse and I'm electronically and efi challenged.  I'm sure that there is more
involved but, basically with this pcm, the 'major' factors that determine
C/L seems to be the ECT and TPS sensors.  This EFI is a MAP speed density efi
with the MAP having the major role in determining AFR while in C/L.
It seems that C/L is entered when the ECT reaches about 70F and stays
in C/L until the TPS indicates 70-75% opening (I'm doing dynamic testing
to see if I can determine this with a scanner).

What I want to do is to run at WOT but to somehow make the computer
think that it is not in WOT mode and hence O/L.  My thought was to see
if some solid state device could be constructed to limit the voltage sent
to the PCM from the TPS somewhere short of where O/L is triggered.  The device
would consist of a battery-powered arming switch which, when turned on,
would activated a solid state device which is tapped into the output wire
of the TPS.  The solid state device would allow for an adjustable internal
preset voltage to be 'dialed in'.  Any TPS output voltage less than this
preset
voltage voltage would pass directly to the PCM and only the preset voltage
would
be sent to the PCM if the device detects any TPS voltage greater than or equal
to this preset voltage.  That's the only way that I could come up with
to keep the PCM in C/L.

AFR mixture would be correct up to this preset voltage for the vehicle.
Whether the AFR mixture is more than adequate afterwards because the tb
will be wide open is beyond me.  In my case, I've tested with larger size
injectors (even with stock injectors I'm running more rich than lean). 
I realize that not knowing whether the AFR is adequate is a dangerous
situation but I am being very careful in my R&D.

The reason that I want to stay out O/L is the computer that I have
retards timing too much and puts out too high a AFR at WOT.  In C/L,
everything checks out and there are significant performance gains.

I sure would appreciate seeing some inputs in this specific area.

Thanks.

Bob
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org