Pulse Wdith.

[John Dammeyer]

>John Dammeyer <johnd at autoartisans.com> wrote:
>
>>If it's a standard O2 sensor why not replace it with a pot that provides
>>0..1.0V and set the output to 0.5V which is supposed to be 14:7:1.  Then,
>>because the O2 is telling the ECU that the mixture is perfect it won't keep
>>screwing around with the mixture pulse width and you can see the real result
>>of your tuning.
>
>I have little experiance in these things, but don't OEM controllers richen the
>mixture until they see the O2 sensor make a "transition" from low to high, and
>then they lean the mixture until the voltage goes back down.
>
>Holding the O2 sensor voltage constant would have an unpredictable effect.
>Possibly the computer would flag it as faulty and use some sort of backup
>system.


I don't believe that's true.  The HEGO sensors have a voltage output of 0.5V at
14.7:1 and then the voltage changes rapidly on either end and so the sensor
appears to have a on/off value.  Perhaps some engine controllers do just use a
simple go/nogo approach but I doubt it.  I can adjust the mixture so the O2 puts
out 0.55V or 0.6V etc.  I have no clue if 0.55V is 14.1:1 or 10.1:1 but I do
know that with a properly set up engine with an Ellison Throttle carb. or else
an SU carb that at maximum Torque the O2 sensor is at about 0.75V.  I've set my
fuel injection to be roughly the same.  Exhaust Gas Temperature and a Post Run
check of the spark plug colour all confirm the mixture is 'about' right.

Cheers,

John