[Diy_efi] Making a fake O2

[Marcello A. Belloli]

Hello again,
     I am surprised at the number of responses I got.  Thanks everyone for
your interest.
     What I am trying to do is get a look at the base fuel map without
getting inside the computer.  I've played a lot with GM ecms, and yes
it is very easy to force the issue in software.  Just set the BLM,
and INT limits to 128.  It might then see the o2, but it can do
nothing to compensation for it.  I had a feeling I'd get all kinds of
responses.  I know I can fake the computer with a simple oscillating
signal. The real question is if a send a perfect signal, will the
computer drift anyway.  I'm worried that the signal might be good,
but the computer will drift a little rich, or a little lean.
     I'm playing with Honda/Acura OBD I computers at the moment.  The data
stream doesn't show any form of a trim adjustment being made.  There
is a fuel map, but not a trim map like what I've seen on the GMs. 
But the car is very responsive to O2.  A friend of mine has just
modified his motor.  He said, "Just a minor change".  Yeah right. 
Forged pistons, higher compression, new cams, etc,..  Well, he's got
it running.  But it's pinging a lot.  Ha!  He doesn't really
understand what he has done.  All he is thinking about is power. 
More power!  Have to have more power! I'm on vacation in Thailand,
and I told him don't go running it until I get back.  So what does he
do.  He goes and runs it anyway.  We are now on motor #2, and I'm
still on vacation.  Now he says its running lean, and so he puts in a
new set of bigger injectors.  He's just throwing stuff at it.
     I'm trying to formulate a way to get this thing really right.  I
don't want to do across the board adjustments.  I've spent enough
time with the GM computers to see it is never just richen it up.  You
usually have to pull back some fuel at idle too.  Those bigger
injectors are great at top end, but not when you are idling.
    I want to be able to run this thing on the dyno, and get it really
close to a right adjustment.  And then we can make little adjustments
on the track.  The problem I was having before was the O2 would start
adjusting faster than I could be sure I had a good reading at any
given rpm/map reading.  So I'm thinking got to take the o2 out of the
equation.  And so here I am...any further thougthts anybody?

Thanks,

Marcello










> Hello everyone,
>      I have been trying to figure out how to make a computer run on its
> base fuel map, and not use the O2 sensor.  I was wondering if it
> might be possible to send a signal that looks like perfect mixture
> all the time?  A signal that looks like no adjustment need to be
> made.  You could put this in place of the O2, so you could see the
> fuel map output without correction.  Is this possible?  I'm figuring
> do a reset of the computer and install this device.  Then take all
> your readings.  What does everyone think?  Am I a crazy?
>
> Thanks,
>
> Marcello
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