O2 Sensor Bias

[Bruce Plecan]

-----Original Message-----
From: Kurek, Larry <LKurek at ocfexch2.ocf.anl.gov>
To: 'Cl-F-Body' <cl-f-body at f-body.org>; 'DIY_EFI'
<DIY_EFI at efi332.eng.ohio-state.edu>; 'Fourth Gen' <fourth-gen at f-body.org>
Date: Monday, August 24, 1998 7:48 PM
Subject: O2 Sensor Bias


>Got a good question for you...
>
>A lot of guys play with fuel pressure to alter their WOT O2 readings. I
>understand that GM runs the stock motors a bit rich, and a lot of guys
>lean them out to get more power. So, if the purpose of lowering your
>fuel pressure (which affects the atomization of the fuel injected), is
>the way to get lower O2 readings, doesn't this affect overall
>drivability?

Ahh, grasshopper, yes adjusting fuel pressure causes a universal
change, so the correct answer is correcting what is needed to be
corrected.
>
>Second, in the factory Helms manual, it states that the PCM applies a
>reference 450mv to the O2 sensors, and then reads the voltage variance
>from this point to determine the fuel ratio. If this is the case,
>shouldn't it be possible to just place a resistor inline with the O2
>sensor to "trick" the PCM that the O2 sensor is reading a higher voltage
>than it really is, and thereby lean the mixture accordingly?

Yes, the ecm is only looking at how often the O2 output crosses that
.44v signal.  The ecm uses the O2 signal as more of a switch and
doesn't care about voltages other than the .44 crossing.

 Maybe I'm
>barking up the wrong tree here...but is this possible?

Barking up the wrong tree, is an every day occurance here at
CSH, HQ.

 How?

Just the hyperactivity showing

 Any
>problems?

Nope, mental health folks know to espect it from this end of
town.
>
>TTYL!
>
>Larry
>
Cheers
Bruce     Staff and I after the recent FBI raids had to take IQ tests,
               and the results were negative.........