Kyle Kozubal wrote:
> <snip>Ok, I would really like to have one of these monitors mounted in the cab
> of
> the truck. However, can someone explain to me how these A/F guages are
> useful and/or accurate if our 02 Sensors are constantly fluctuating from
> 0-1V(thus the guage will also be fluctating all the time)? I guess I just
> need some further help understanding how these A/F guages are useful if
> there is not constant voltage coming from the 02 Sensor. I just keep looking
> at this link and the guage jumping all over:
> http://www.autometer.com/hp/techtips/air_fuel_hookup/air_fuel_hookup.html
> and wonder how is this helpful??!!
Kyle,
First off let me say that I too have been watching your posts re: truck stalling
and am glad that you have the shop chasing after the same thing (stalling) that
you knew about long ago. Re: A/F gauges - its too bad that you didn't have one
before because I think it would have helped you reach (long ago) the same spot
the shop is at now. You did mention one time that you had hooked your truck up
to a scan tool and the O2 sensor output was constant. I mentioned that this was
a problem (or the scan tool was wrong). Considering that only a bad O2 sensor
or a PCM that for some reason was not doing its job of controlling A/F by
oscillating around stoich could cause such a condition - you can quickly see how
just one new O2 sensor could have had you looking at the PCM sooner. Maybe a
quick swap w/a friends PCM would even tell you more.
That speaks volumes about an A/F gauges usefulness. Think of it as a dyno-level
tuning aid attached to your vehicle full-time giving you readouts visually.
Everyone here likes to guess whether they are running "rich" or "lean" after
dinking with some component, adding some potential horsepower-increasing mod,
etc. After making mods - jamming on the gas a few times will make someone
wonder just how "lean" they are after a few guesses - they start modifying
something else to compensate?? Why guess? On my truck - after several mods I
too wondered how far away from "overly rich" I was at WOT. I know now that I am
still safely within the "overly rich" condition so I continue to mod without
even looking at the fuel side. My gauge will tell me when enough is enough.
To specifically address the part where you mentioned "jumping all over the
place...
how is this helpful" - this is your indication that your PCM has your truck in
closed loop mode where it is monitoring A/F ratio and making adjustments
accordingly. It isn't always doing that (just 90+ percent of the time 8). When
you jam on the gas (as well as lifting your foot) - you'll see it go either way
rich
or way lean (ie not jumping around or oscillating) indicating open-loop mode.
I also would disagree w/Bob re: the effectiveness of an A/F gauge when outside
of stoich or 14.7 to 1. These relatively cheap O2 sensors are ONLY good for
telling you which side of 14.7 to 1 you are at. They only get excited at that
threshold and are extremely inaccurate for anything but 14.7 to 1. This is why
the PCMs oscillate around it - plain an simple. Two O2 sensors from the same
supplier might give different readings when say "4 LEDs" away from stoich. ONLY
a wideband sensor can give an accurate representation of where you are when away
from stoich.
Just my $0.02 and I hope it helps someone,
Shane
-- '96 IndyRam-HisIndy-MPI/TB/Pulleys/AccelCoil/MPComp/HookerSuperComps/CompTAs '96 IndyRam-HerIndy-numbered(#142)"Track Truck" '74 Triple-Black Dodge Challenger Rallye 360 home-brew EFI R&D vehicle '68 Black Corvette Convertible 427 (For Sale)
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