Proper Mixture.

[Andrei G. Chichak]

At 21:56 7/29/96, John Dammeyer wrote:
>Tom Cloud mentioned that he had an Oxygen sensor that he monitored under
>cruise.  It's no big deal to add a 12 bit A/D to my processor and read the
>voltage value.  Question is.... how do I interpret this?
>
>I can see if there is zero O2 left then I have complete combustion for the
>amount of O2 in the intake stroke but if I have a too rich mixture wouldn't
>that happen anyway?
>

My bro put an O2 sensor into his Mini and wired it to a recalibrated high
impedance panel meter.  He was having some problems with misfire at high
RPM and figured he was leaning out.  The meter immediately told him he was
WAAAAAAAAY too rich.  He adjusted it to run properly and great googly
moogly Powerrrrr.  Big problem now was it was too lean to idle.  Out came
the needle file...

Biggest problem using a A/D would be slowing the bloody thing down.  On a
BS you would definitely see every exhaust pulse, and if you used it for
closed loop control you would adjust the hell out of the system.  But then
of course you, of all people, know about analogue and software filtering
and control.

On a BS you would have to take a look at the area of the exhaust port and
area of the sensor intruding into the gas stream.  The sensor has to be
close enough to the head to heat up quickly and stay hot, and small enough
to not impede the flow excessively.  You could alter the shape of the
exhaust manifold to have a larger area around the sensor but watch out for
a drop in exhaust gas speed.

Since BS uses an F head, you will have a problem with fuel wetting of the
inlet manifold and the blobby charge response that this gives (as well as
updraft manifolds and heads with 180 degree bends).  The O2 sensor should
give you the feedback you need but you will need to do some heavy
filtering.  You may have to run it a bit rich to have it work properly.

A

--
Andrei Chichak                   | Information Systems
agc at mercury.uah.ualberta.ca      | University of Alberta Hospitals
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