The ecu expects to see above .6v fully warm engine with throttle plate fully open. With throttle plate closed it expects to see below .4v. This info is for the secondary O2.I'm not sure if it is the same for the primary O2. The real question is how much fuel mixture/timing control is controlled by what the primary and secondary O2 sensors see and signal to the ecu, can we essentially tune our engines by manipulating the signal from the primary and or secondary O2 sensors with someting as simple as wideband with variable analog outputs

 

Anyone?

 

The o2 sensor system is a feedback system by design. The primary o2 sensor is used by the ecu to determine the amount of oxygen in the exhaust to adjust the fuel trim. The secondary sensor is only there to check up on the catalytic converter. I have not heard of anyone "modifying" the signals to get power. If there was a substantial gain possible by adjusting the fuel trims, then the best way to achieve this would be by different software in the ecu. The voltage of the primary sensor is constantly swinging back and forth from about .2 volts to about .8 volts. Very minute voltage. I personally don't think that tampering with this system would net gains in horsepower that would outway the risk of frying the computer. I also believe that Honda did their homework when programming software for our cars.
If somebody out there has actually done some mods to this system, I would be very interested in hearing the results.

Kev

 

The ECU is not programmable.

 

The voltage adjustments is pointless. If you mess with the adjustment you could run full rich all the time or full lean then you can kiss your motor good bye.

You also have to calculate air pressure, elevation, day or night driving, etc. Do you want to do that constantly or do u want a computer to do that?

Don't mess with any O2 sensor adjustments. Let the car be.

 

Since when is an ECU not programmable?

 

um , i think as far as we are concerned the ecu is not programmable, or i should say , its programmed once and then no more.

 

I think the gist here, is don't screw with it. It works just fine.

 

The S2k's PCM does not have the ability to be re-flashed.

Although possible to screw with the 02 inputs to fool the PCM, It's not advisable. It won't take the PCM long to pick up the false input resulting in a CEL and the PCM ignoring the false input.

 

The secondary oxygen sensor is an emissions control device it cannot be used to control tuning. Messing with it will simply give you a CEL or not give you a CEL for cat efficiency depending on what input you give it.

The primary oxygen sensor is what is used for tuning. Unfortunately narrowband O2 sensors cannot be used effectively for tuning. Their band is too narrow. Thats why the ECU only uses it for partial throttle tuning in the general area of 14.7:1. After a certain throttle position the ECU goes to a look up table to determine how long to open the fuel injectors. The look up table is only applicable to a stock engine. As you change things (ie. headers and such) that look up table is less and less aplicable to your engine. Change your engine too much and your A/F ratios will be too lean. Reprogamming the ECU changes that look up table.

The limitations of the narrowband O2 sensor prevent it from being used as a tuning device. Its not even really adequate as a warning device ala air fuel ratio meter.