|
As
you can see, the sensor is almost like a switch. It's output voltage
lowers as your A/F ratio increases, but at 14.7:1, it drops dramatically.
If you use this sensor to tune, you can tell if your lean or rich,
but you can't tell by how much. It's not designed to do more than
this, so it's cheap and the manufactures can slap it in their cars
without a lot of cost. If you hook a voltmeter or an A/F gauge (which
is just a pretty volt meter) up to this, when the engine is operating
in closed loop mode (using the sensor to adjust fuel mixture for emissions),
you will see the voltage pinging back and forth from lean to rich.
It's trying to get the engine to stay at 14.7:1, but doesn't know
how much to adjust the A/F ratio because the sensor just doesn't provide
that information. It just shows the engine is lean, so the computer
richens up the mix. Then checks the sensor again, oops, now we are
rich, lean up the mix, check the sensor, oops, too lean, ping pong
ping pong....
The solution is a wide band O2 sensor, or UEGO. This is actually made
of 2 different types of sensors built into 1 package, and requires
specialized circuitry to interface to it, it's not simply a voltage
output any more, so don't bother with the volt meter. It's pretty
expensive, so most car manufacturers don't use them (some lean burn
Hondas and the new 1.8T VW's do). We bought powertrain electronics'
AFM1000 UEGO sensor interface hardware to power our UEGO sensor, check
out it's output voltage vs. A/F ratio.
|
1039
riverside street suite10 
