On Sat, Feb 15, 2003 at 08:18:55PM -0500, ptegler@cablespeed wrote:
> 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
Paul,
I was curious about this and stuck one of my oscilliscopes on the
output of the sensor and I wonder if the S8942 is a wideband sensor
because the output was DC, with some tiny (200mV PtP?) pulses with
ringing on it.
> 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
> >
> >
> > --
--
I've found something worse than oldies station that play the music I used to
listen to. Oldies stations that play the "new" music I used to complain about.
lrc@red4est.com http://www.red4est.com/lrc
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