O2 sensor question

[TURBOV6]

I have the Casper's heated O2 sensor (ford O2) and wanted to know when it will be time for a replacement. My O2's are good and consistent, no trouble codes and been through 4-5 races with 110 leaded gas. I'm planning in replacing it with another headed O2. Which brand should I go with?

 

[gofstbuick]

O2 sensor proper operation is about range and response. It doesn't matter whether it's heated or not. The heated unit will just get to operating temps faster. Lots of guys use cross counts, but the most accuate method is to use a propane enrichment tool and a digital storage oscilloscope (DSO) or graphing multimeter. To determine range, set the DSO range to 0-1200millivolts (mv) and set the time range to 200 milliseconds per division. Then hook the wires up to the O2 signal and hook the ground lead to a good ground (the O2 sensor should remain connected, I use a paperclip in to the weather pak). When the sensor is properly warmed, it will switch at idle above and below the 450mv. Flow propane into the snorkel or into the induction path. this will create a rich mixture and cause the readings on the DSO to flatline above 800mv. The correct flatline range is 800mv to 1000mv. Then turn the propane off and the readings should drop below 200mv, because the O2 now senses a lean mixture. The correct drop should be between 200 to 0mv. Any shift in the range would be reason to change the sensor. Example: the high flatline is 1100 mv and the minimum reading is 375mv, this would indicate a bias riche sensor, or the flatline is 650mv and the minimum drops below zero, this would indicate a bias lean sensor. Now lets test response. The O2 sensor must respond from full lean to full rich in less than 100ms, usually around 60ms. Any number over 100ms means the sensor is lazy, and in our case the fuel requirements will probably be limited during mid range acceleration. Again, flow the propane until it flatlines, turn the propane off and the readings will begin to drop. As the reading begins to make its turn (at the bottom) snap the throttle, the engine should sense fuel enrichment and rise rapidly. Take your time reading at just after the lowest turn and just before the highest turn. The results of the slope change should be LESS than 100 milliseconds, if not, change the sensor, because the response time is too slow, and you will not acheive the full potential of the fuel system.
Sorry for the long winded reponse
Think of how easy it would be to test the TPS

 

[MSDGN]

Just keep track of O2 cross counts and range of values...you'll know when the sensor is ready for replacement...it won't necessarily throw a code but will have low cross counts(lazy)
or the range of values will be way off...I had some runs recorded on Tlink...no knock the whole run at 25 PSI boost but the O2's were at 300-400 so I knew the sensor was bad...Casper's sells a good replacement heated O2 sensor...the NTK's...they seem to last longer than the AC Delco's...at least in my car and some others I know of...

 

[gofstbuick]

But if you disconnect your O2 sensor, your scanner will still provide a crosscount.

 

[strikeeagle]

Best thing to do is speak to Spina. Is your sensor a 3 wire or 4 wire? John has used both, as well as Bosch/Ford, Delco and Ford/NTK sensors over time, so he's in the best position to tell you what will and won't work with your harness.

BTW, I like the Max Effort - you can throw your O2 sensor away if you like and plug the hole. Besides, O2 sensors are not the best indicator for racing purposes, better EGTs and/or a wideband...

 

[gofstbuick]

What strikeeagle says is true because the computer goes into fuel enrichment mode after seeing 3.75v from the tps. But I would think you want to know that the computer has the ability to respond to fueling requirements up to that point. Jus my 0.02.

 

[strikeeagle]

Absolutely, the ME is an open loop device...