O2 / Lambda Sensor Data

[pat ford]

 can you post details ( schematics etc..) on these kits?

---- Begin Original Message ----
 From: "Will Reeve" <will at reeve.org.uk>
Sent: Wed, 25 Apr 2001 21:30:58 +0100
To: <diy_efi at diy-efi.org>
Subject: RE: O2 / Lambda Sensor Data

With respect to what other have written, the science does back up what
everyone has said, but I believe that lambda sensors can be successfully
used as an very cheap aid to engine tuning. I talk from hands on experience.
A friend and myself have been working with lambda sensors as a means of
obtaining an indication of mixture with some very interesting results. Some
background:

Two cars, similar states of tune. Same engine, management, exhaust, inlet,
grade of petrol etc. etc.

An addition lambda sensor was installed into the exhaust down-pipe adjacent
to the factory one. This was achieved by drilling and welding a boss in
place. Two different sensors were used, a Bosch one and a webcon pattern
one. Both heated (2 wire heater, 1 wire signal, signal ground via exhaust
itself). Two lambda sensor "meters" were made, from the kits designed by the
"Silicon Chip" magazine in Australia. These use a PIC which has the volts
'v' mixture curve table and outputs a air/fuel figure between about 11.5 and
16.5.

The cars run Motronic M1.5 which only really goes into "open mode" at WOT
(wide open throttle). We made a series of EPROM'S which contained different
WOT fuel maps, each one adding a few ms onto the injectors duration at WOT.

It was possible to place one chip into one car, warm up the sensor for a
good few minutes, you can see when it is nice and warm as the open loop
cycles between 14.6,14.7,14.8. At WOT the meter "locks" onto a fuel ratio
which stays pretty constant through the rev range.
The same chip in the other car gave the same results! Add a chip with more
fuel at WOT and up goes the meter reading! Replace it with a chip with less
fuel at WOT and down goes the meter reading. Repeatable results, even on
different days. I think that the temperature of the sensor is quite well
regulated and constant enough to give some meaningful results EVEN off
stoichiometric. Not state of the art I agree, but for a total cost of less
than 60quid for sensor and meter it can't be beat IMHO.


P.S. Some quick pictures of the installation can be seen at:
http://www.btinternet.com/~wreeve/afmeter.htm excuse my lucky mascot!
P.P.S. The reason we went to all the trouble was because we removed the cats
and replaced all the silencers with straight through versions, did a bit of
head porting, and fitted a free flowing air filter....this we thought might
have changed the fuel requirements at WOT. Because a) the lambda sensor is
ignored, and b) the AFM is ignored. This turned out to be a good assumption
as at standard settings the WOT mixture was BELOW stoic, its now set up at
around 12 and lower at WOT!



-----Original Message-----
 From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
Behalf Of Bruce Plecan
Sent: 25 April 2001 16:01
To: diy_efi at diy-efi.org
Subject: Re: O2 / Lambda Sensor Data



All the one wire ones can reliably do is tell you when your rich (over .5v),
or lean (less then).    Anything else is like reading tea leaves.
When your done tuning, you might record what O2 voltage is was, and a
general reference but again, it's very general
Bruce



> I'm after some data on a 1-wire O2 sensor.  I'm planning to construct the
EGO meter
> as per diy-efi web site, but I still have some questions
> I'm planning to use a universal 1-wire sensor. But I can not find any
technical
> data on them.
> 1.  Does the sensor require a bias or excitation voltage?
> 2.  If the output voltage is self generating (albeit at high impedance)
what
> voltage corresponds to what oxygen level?
> 3.  what is the correlation to oxygen level and mixture ratio?
> I have already built the circuit but have yet to buy a sensor, any
recommendations
> would also be appreciated.
> Thanks.

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---- End Original Message ----



Pat Ford
12 Strathcona St
Smith Falls,On
613-283-4703
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