There are a few different O2 sensors available. The most basic is the single
wire narrowband, its non heated. Then you have the three wire narrowband,
which has a heater element to bring the sensor up to operating temp quicker.
Then you have the wide range(read expensive) sensors, which give you a very
accurate AFR reading over a wide range. Normal sensors found in most EFI
vehicles are narrowband, they are accurate around the 14.7:1 air fuel ratio,
which is the ideal mixture for catalitic converters to operate(best power is
made around 13:1 and for lean crusing you can go to 15:1 and up depending on
the engine). The narrowband sensors become somewhat innaccurate either side
of this 14.7:1 figure, however can still be used as an effective tuning
device. You can just hook a digital multimeter up to one and read off the
voltages, around .5 to 1v. Or as many do, build a simple circuit to give a
graphical readout using LEDs.
The sensors arent a thermocouple, they output a voltage in relation to the
amount of oxygen left in the exhaust gas.
Most sensors dont like leaded fuel, so you need to replace them after a
certain amount of exposure to it, youll get many hours out of one before its
contaminated tho, enough to tune a car, after which it will get "lazy". They
can be cleaned and tested using a small butane blow torch, after about 20
seconds of heating the output voltage will go up to about .9v on a healthy
sensor.
A kit has just been developed by an electronics magazine in Australia to
read the wide band sensors, it uses an expensive bosch sensor and gives a
numerical readout of the AFR. Go to
http://203.41.157.5/jaycar/FMPro?-db=products.fp3&-format=detail.htm&-lay=cg
i&-sortfield=model%20%23&Category=KITS%20-%20AUTOMOTIVE&-recid=46837&-token=
12590328&-find=
to see it. It would probly cost you US guys about $2 delivered with the
current exchange rate ;-)
Another, supposedly better kit will be released next year by
www.autospeed.com
If anyone needs anymore info on these things feel free to ask.....
Adam Fox
----- Original Message -----
From: Brian St. Jacques <brian@varatouch.com>
To: <datsun-roadsters@autox.team.net>
Sent: Wednesday, October 04, 2000 6:36 AM
Subject: Engine Tuning Device
> Hello All,
>
> I have seen some of those fuel mixture monitors that interface to O2
> sensors, and this seemed like something that might help considerably with
> the carb tuning. I am currently in process of designing my own, partly as
a
> term project and partly because I plan on actually using it. I am actually
> adding a few more features to the device to gather a little more
> information for diagnostics. The unit in the car will have a bank of LEDs
> to indicate fuel mixture, but I am also picking up the RPMs and throttle
> position. I have a connection to interface to a computer and have written
a
> program to continually graph the last 10 seconds worth of data for the
fuel
> mixture, RPMs and throttle position. I have most of this done already, but
> I am doing some things with an electric motor to simulate the results so I
> don't have to bring a car into class.
>
> My question is this- Does anybody know of a throttle position sensor that
> they think may be adaptable to an SU setup? I could rig up a potentiometer
> with some linkage, but I figured that a real throttle position sensor
would
> be better fit to live in an engine compartment. If anyone has any
> suggestions, please let me know.
>
> Brian '68 1600
>
>
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