AEM V1 Help: O2 #1 Rich/Lean Limit vs O2 FB Rich/Lean Limit?

Hello, I've looked through all of the available documents looking for information on what exactly the "O2 #1 Rich Limit" as well as the "O2 #1 Lean Limit" settings (which can be found in the Full list of Options) actually do?I understand the function of the O2 FB Rich/Lean Limits, which are meant as restrictions for how much fuel the O2 Feedback function is allowed to add or remove (when the feature is turned on). What I can't find info on is the other settings mentioned above. The O2 #1 Rich/Lean limit values are completely different then the O2 FB values. In the AEMPRO user guides Version 1.14 and version 2, they make no mention of what this setting does.Any have an idea?

It could be a virtual limit used by the ECU for fuel calculations. For example if the ECU receives a signal from the O2 sensor of 25 AFR, then the ECU will use the 02 #1 lean limit value of 21.9 instead.

@DynoDoug Originally, I thought that perhaps it was a manual cap we could set to tell the ECU (as you pointed out) what the limits should be. However, these numbers should be automatically set when we use the Wizard to set the sensors. If AEM lists the specific O2 sensor in their wizard, I would think that they also have the values for the reading limits of the sensor.

The odd thing is that I don't see this Option setting in the AEMTuner program that they created for the Series 2 and series 4 EMS, I only see it in the AEMPRO that works with the Series 1 EMS (which is the one that I'm currently using). Also, the delivered values from AEM in the calibration file for my unit, are set to the same value for both Rich and Lean Limits.

Hopefully someone from AEM can chime in (even though they no longer support the Series 1).

I have a series one in my WRX but it's out of commission right now. Once I get the engine back in it, I will do some experimenting and see if I can figure out that option.

You are correct, AEM dropped support for the series 1 about 10 years ago. It makes it quite challenging for those of us who are still working with one because the user's guide doesn't explain a lot of things.

Best of luck! Let me know if you figure it out.

I played around with the O2 Sensor wizard while I had the O2 sensor table opened. What I noticed was that they values in the table would change every time I selected a different O2 sensor from the wizard. At the same times, these O2 #1 Lean and Rich Limits would also temporarily change.

So I'm going to guess that these values should be set based on the actual Lean and Rich limits of your specific O2 sensor. In my case, since I'm using the Innovate LC-1, I used the values provided in the manual for AFR (gasoline) which are 7.35 and 22.9. Since the Sensor calibration table goes from 0V to 4.99V I set the lean limit (4.99V) at the 21.9 AFR that the table allows, and the Rich limit at the 7.32 AFR.

So far after testing this, I've seen no adverse effect. As mentioned previously, the Series 2 which use AEMTuner instead of AEMPRO, doesn't have these setting anymore. Seems like AEM decided to just stick with whatever values the Wizard provides.