foxtrot

Ok I just got my Bassani modular cattedX, comes with straight thru cat replacement tubes if I want to run with no cats. I know didly about the o2 sensor system its purpose and function

1. The O2 sensor measures O2 duh.....and is used to look at emissions how?
2. Why is it up stream from the cats if the cats are doing the emissions control.
3. I know I can use MILs to fool the microP but can I re-program the O2 sensor instead?
4. Bassani says even though the cats are street legal it may trip the microP. I would rather reprogram this as a fix than spend $100 on mils. While I am re-programing for O2 I am sure there are other good tweaks right? Timing?????

I am a EE anyone know what the MIL's are specified to with respect to the output signal?

jdaniel

1. The O2 sensor measures O2 duh.....and is used to look at emissions how?

An Oxygen sensor is a chemical generator. It is constantly making
a comparison between the Oxygen inside the exhaust manifold and air
outside the engine. If this comparison shows little or no
Oxygen in the exhaust manifold, a voltage is generated. The
output of the sensor is usually between 0 and 1.1 volts. All
spark combustion engines need the proper air fuel ratio to
operate correctly. For gasoline this is 14.7 parts of air to one
part of fuel. When the engine has more fuel than needed, all
available Oxygen is consumed in the cylinder and gasses leaving
through the exhaust contain almost no Oxygen. This sends out a
voltage greater than 0.45 volts. If the engine is running lean,
all fuel is burned, and the extra Oxygen leaves the cylinder and
flows into the exhaust. In this case, the sensor voltage goes
lower than 0.45 volts. Usually the output range seen seen is
0.2 to 0.7 volts.

The sensor does not begin to generate it's full output until it
reaches about 600 degrees F. Prior to this time the sensor is
not conductive. It is as if the circuit between the sensor and
computer is not complete. The mid point is about 0.45 volts.
This is neither rich nor lean. A fully warm O2 sensor *will not
spend any time at 0.45 volts*. In many cars, the computer sends
out a bias voltage of 0.45 through the O2 sensor wire. If the
sensor is not warm, or if the circuit is not complete, the computer
picks up a steady 0.45 volts. Since the computer knows this is
an "illegal" value, it judges the sensor to not be ready. It
remains in open loop operation, and uses all sensors except the
O2 to determine fuel delivery. Any time an engine is operated
in open loop, it runs somewhat rich and makes more exhaust
emissions. This translates into lost power, poor fuel economy
and air pollution.

The O2 sensor is constantly in a state of transition between high
and low voltage. Manfucturers call this crossing of the 0.45
volt mark O2 cross counts. The higher the number of O2 cross
counts, the better the sensor and other parts of the computer
control system are working. It is important to remember that the
O2 sensor is comparing the amount of Oxygen inside and outside
the engine. If the outside of the sensor should become blocked,
or coated with oil, sound insulation, undercoating or antifreeze,
(among other things), this comparison is not possible.


2. Why is it up stream from the cats if the cats are doing the emissions control.

There are four O2 sensors. Two before the cats and two after the cats. All you really need to be concerned with is the downstream O2's.

3. I know I can use MILs to fool the microP but can I re-program the O2 sensor instead?

You can with a tuner or through a tune... but MILS are so much more basic and gets the job done faster unless you have a tuner handy.

4. Bassani says even though the cats are street legal it may trip the microP. I would rather reprogram this as a fix than spend $100 on mils. While I am re-programing for O2 I am sure there are other good tweaks right? Timing?????

MILs shouldnt cost you but $50 and thats the expensive ones. But you can do it with a tuner and yes, you can adjust timing, fuel and so on with a hand held.

I am a EE anyone know what the MIL's are specified to with respect to the output signal?

I have no idea what you just said there. LOL

foxtrot

Thanks jdaniel, good info.

Does the O2 circuit change any engine parameters "closed loop" or does it just throw errors if out of spec (open loop)? I have heard both...

BTW EE is short for Electrical Engineer.

PS Sorry about your old car, ya got a newer one now right?

jdaniel

Well.. Some will say that it wont change the engine parameters at all but from my experience with O2 sensors last week with the Saleen, if you have a bad one or an open loop then the engine will think its running lean and dump TONS of fuel to correct it. In this case, the engine bogged down hard and after a sudden blip of the gas t would reopen till the car returned to idle and it would mess up again till that process is repeated. So make sure you get either the MILs or tune it correctly.

Thanks, I did get a newer car. I picked up a '03 Kenne Bell Cobra. And what a HUGE difference!