Well Larry.... you probably won't like this answer.
the O2 sensor you are 'trying' to use... is as you suspect...
useless for tuning. O2 sensors are simply an on/off device.
The duty cycle of the squarewave they output (turning on and off)
will give you a variation of the 'average' voltage of the sensor
This 'average' voltage centers around 0.5VDC . These type of
O2 sensors are only designed to let the computer know the engine
is rich or lean NOT the absolute F/A ratio. They are also limited
to only around 13-16 A/F. (stoic=14.7)
It sounds like your gauge at least, is filtered. Otherwise you'd see
the 'bouncing' voltage as it turns on and off.
If you need an O2 gauge to tune with...(like I did for my Weber dcoe
and FI projects... you'll need a full 'wide band' O2 gauge. These
are true F/A reading setups and range from 10-25 A/F (25=free air)
Most 'professional' or 'off-the-shelf' WBO2 meters will run you
$700-$1800 Ouch!
BUT... you can do as I did... build your own..or buy the unit
pre-built. Check out http://www.techedge.com.au/
(the unit I bought and use)
as well as http://www.diy-wb.com/ where it all started.
If nothing else...the two links above will give you a good insight
into tuning via A/F.
Paul Tegler
ptegler@cablespeed.com
www.teglerizer.com
----- Original Message -----
From: "Larry Colen" <lrcar@red4est.com>
To: <british-cars@autox.team.net>; <mgs@autox.team.net>; <hans@hi-flow.com>
Sent: Saturday, February 15, 2003 8:12 PM
Subject: Reading O2 sensors
> I'm trying to dial in the carburettor on my MGB now that I've
> installed the blower. Rather than spending $100/hour on the dyno, I
> thought I'd try installing a mixture guage, so I bought the Nordskog
> M7009 guage and the S8942 (4 wire) O2 sensor.
>
> It turns out that the 10 led guage just does not give enough
> resolution to work for the tuning I'm trying to do, so I've hooked a
> DMM up to the output of the sensor.
>
> I tried a quick google search, but am unable to locate a curve that
> matches voltage up with O2 level, or fuel mixture, except in the
> roughest sense. Does anyone have any urls to good detailed graphs
> relating O2 sensor voltage with what they measure?
>
> This is a "1 volt" sensor and seems to have stoichiometric at right
> around 0.5 volts. I'm especially interested in the range of .85 to
> 1.0 volts, as that is where the car seems to be running.
>
> Larry
>
>
> --
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