O2 Sensor Calibration Off
So I took my car to the dyno Thursday and found that the fitechO2 sensor didn't agree with the Dyno AFR at WOT. Both read the same at idle. The fitech was commanding 12.8 at WOT, but the dyno sensor was reading in the 10's. We made a few more pulls and leaned out the WOT AFR's each time. The power kept coming up until the fitech was maxed out at 13.5. The log showed that the AFR was 13.5, just as commanded, but the dyno was showing 12.9. The dyno guy said that he KNEW that his o2 sensor was correct so I can only assume that My O2 sensor has a bad calibration.
Now I worry that if I set my WOT AFR to 13.5 (12.9 actual) and I change out the O2 sensor later on to one that has a correct calibration, I'll end up being way too lean. And of course, now I'll never trust another O2 sensor again until after I've verified it against another.
was .6 fatter than the dyno 02 sensor at WOT. At idle they are both the same.
We leaned out the WOT to 13.50, as far as it would go, and The more we leaned it out, the more power It produced, but I still need to go leaner. This was with a 2 month old Bosch O2 sensor and no vacuum leaks anywhere.
02 sensor readings should be used as a tool not as an absolute. Many factors will create a variance in the reading. So many are quick to blame the sensor and/or Fitech. Simply foolish.
Reading the spark plug is a much more reliable way of Tuning and monitoring the performance of your engine. In this case the Dyno, operated properly, can be a tremendous tool.
I would suggest to anyone using or considering tunable fuel injection to make the online courses offered by EFI University. I believe the cost is $100, and definitely clears up the complexity of tuning maximum power and efficiency.
I have an AEM 30-4110 air/fuel gauge with a Bosch 4.9 LSU O2 sensor installed in my car and it reads almost the same at idle as the Fitech unit, but during driving I notice the AEM is showing more rich by approx .5 to .8 points at mid to high cruise and WOT. Until I get mine verified on a dyno, I'm going to take a number between both O2 sensors. That way I should be pretty safe. At the drag strip I'll adjust WOT until my MPH doesn't change.
Austin, is there any adjust-ability in the Fitech unit to calibrate the AFR readings after I have the numbers verified on a dyno? Also do you know which sensor the Fitech one is? I don't remember if its a 4.9 style?
There is not any way to calibrate the O2 sensor that I know of. The problem is not the sensor, it is the exhaust system and the rest of the combination.
The best way to set your AFR is by the spark plugs. Once you get a good plug reading, use the AFR setting as a base line. It's not the number that defines the tune. The tune defines the number.