Proper Mixture.

[tom sparks]

John:

Here is a web page that will probably answer some of your questions about
the O2 sensor: 

http://ram.chem.tulane.edu:8080/f-body/trivia/o2sensor.html

 From what I've been able to gather, the O2 sensor found on modern cars is
really only good for a narrow band of A/F ratios,  so narrow in fact that it
is really only able to tell you if you are over or under the optimum.  Again
from what I've gathered, this is used to adjust the injector pulse width
slightly until the mix is a little too far the other way.  So, the A/F mix
hovers close to stoich but never really stays on stoich too long.  

Nother thing.  The O2 sensor is some distance from the injector and what is
going on between the two places may bear no relation to either of them.  In
other words, the O2 sensor tells you what already happened some time ago and
the system is left to make some sense of it in real time.

BTW, what injectors are you using for a motor that small and what kinds of
rail pressures are you using?

Best regards,
Thomas Sparks

At 09:56  7/29/1996 PDT, you wrote:
>Hi,
>
>Newbie type question again.
>
>I'm working on improving a 2HP Briggs&Stratten Lawnmower engine.  I have the
>electronic ignition complete and when I finish the TDC/BDC sensor disk I'll
>try it.  As it is it works with a simulator that produces the pulses that
>the sensors would make.  So I can see a nifty advance curve working all the
>way up to 3600 RPM.
>
>Next is to improve the fuel delivery.  But How do I know what the optimum
>mixture should be at any RPM under load.  Do I purchase an O2 Sensor that
>goes in the exhaust?  I have a color tune spark plug and I can use it to set
>idle mixture by looking through the quartz window in the sparkplug and
>adjusting for blue ignition;  too rich is yellow/orange.  However this
>sparkplug would destruct under continuous operation at 3600 RPM.
>
>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?
>
>Thanks,
>
>John. 
>Pioneers are the ones, face down in the mud,
>with arrows in their backs.
>Automation Artisans Inc.      Ph. 604-544-4950
>6468 Loganberry Place         Fax 604-544-4954
>Victoria BC CANADA V8Z 7E6
>
>
>