DIY-WB accuracy of A/R readings

[Mark S. Riley]

Have been driving and comparing all week. I and probably very few other
people have ever had the opportunity to have 2 wide band meters hooked up to
the same car at the same time. I've had the Horiba since 1988 when it cost
me $8800.00 and after watching the DIY-WB for almost a week, I don't have a
problem using the $200.00 meter now to tune with. From ratios as lean as
18.3:1 down to 11.2:1 the voltage versus the indicated air fuel ratio on the
Horiba run within a couple of hundredths of a volt. It's so close that I've
been thinking about swapping holes with the sensors and see if I still see
the same thing happening. These are mounted in the 2 bonger stinger on the
end of the muffler. I have been wondering if at light throttle, if the
exhaust is truly  homogenized when it goes out of the muffler. At light
throttle, I see small differences in the readings between the two meters.
But, at WOT, they match very, very closely. Remember, this is on a car with
a good working catalytic converter. So what comes out the tail pipe has
already been subjected to the treatment. That's why I'm thinking about
swapping sides with the sensors and see if the trend continues. When you
only had one sensor, you just have to believe it. With the two of them, I
find myself looking at the difference at 16.48:1 and 2.63 to 2.67 volt and
it changes a little from block to block and I'm wondering just much
difference it can make at 16.5:1 anyway. You need to look at the spark plugs
still for the definitive answer. I really am not going to be concerned with
the slight difference noted. The difference in tunability with this sensor,
(possible slight difference in output), compared to using what to tune with
before now? A 10 led readout off of a single wire O2 sensor? Tarot cards,
fortune tellers or seemingly rolling the dice have all been popular tuning
aids before the advent of the Wide Band O2. I don't know that the Horiba was
linear in output but I have happily used it, trusted it and have not blown
up a bunch of engines over the years. Perhaps the "sweet spot" like in an
analog meter is around the center, I don't know. But if you need a lab grade
instrument, Horiba and NTK can solve your problem. and it uses this
sensor... for a ton of moolah...
I'm real happy with the results. I hope BC publishes the led readout
schematic soon. That will work real nice. I have been thinking about the
readout from Australia that Peter Gargano found and reported about. I
haven't found a cheaper way to put a numeric readout on it yet. I would like
both. I haven't tried to datalog it with a Dataq 4 channel board yet, but I
will. Should be interesting. What we were discussing this afternoon, was
using a video camera to record the guages and WB while testing so it can be
replayed over and over to see the differences and exactly where it happened.
I've run on long enought. later, Mark

----- Original Message -----
From: "Bruce" <nacelp at bright.net>
To: <diy_efi at diy-efi.org>
Sent: Friday, September 08, 2000 4:39 PM
Subject: Re: DIY-WB accuracy of A/R readings


>
> The output isn't linear in nature.  Just a characteristic of the beast.
> Within just the last few days Mark posted it matched his Horiba (I think
> that's what his other WB is).
> It not a lab grade devise, so it's not perfect, and was never meant to be.
> It was mean to be affordable, and it's output repeatable.
> Bruce
>
>
> From: Hugh Keir
> Subject: DIY-WB accuracy of A/R readings
> I have also been looking at formulas that will allow the A/R to be
> calculated, but I have a question over the accuracy of the readings
> presented at ftp://diy-efi.org/pub/diy_efi/project_files/diy_wb1/v_out.txt
> As a start, I looked at how regular the increases in A/R were and I
noticed
> a bit of a wobble at A/R 14.4. but the readings are generally meandering
> about.
> I hope the output from my spreadsheet makes sense.
> Can we re-confirm these readings as my gut feeling is there should be a
> steady progression in the numbers.
> No point in presenting formulas for inaccurate readings
> Hugh
> Difference betweenDifferences between
> VoltsA/RA/R readingsthe differences
> 1.40 10.08 0.15 0.00
> 1.45 10.23 0.15 -0.00
> 1.50 10.38 0.15 0.01
> 1.55 10.53 0.16 0.01
> 1.60 10.69 0.17 0.00
> 1.65 10.86 0.17 0.00
> 1.70 11.03 0.17 0.01
> 1.75 11.20 0.18 0.01
> 1.80 11.38 0.19 0.00
> 1.85 11.57 0.19 0.01
> 1.90 11.76 0.20 0.01
> 1.95 11.96 0.21 0.00
> 2.00 12.17 0.21 0.01
> 2.05 12.38 0.22 0.01
> 2.10 12.60 0.23 0.01
> 2.15 12.83 0.24 0.00
> 2.20 13.07 0.24 0.02
> 2.25 13.31 0.26 0.01
> 2.30 13.57 0.27 0.00
> 2.35 13.84 0.27 0.02
> 2.40 14.11 0.29 0.01
> 2.45 14.40 0.30 0.25
> 2.50 14.70 0.55 0.04
> 2.55 15.25 0.59 0.05
> 2.60 15.84 0.64 0.06
> 2.65 16.48 0.70 0.05
> 2.70 17.18 0.75 0.08
> 2.75 17.93 0.83 0.07
> 2.80 18.76 0.90 0.10
> 2.85 19.66 1.00
> 2.90 20.66
>
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