AEM UEGO Controller

[1ViciousGSX]

Well I finally got my AEM UEGO controller package and add-on gauage installed a couple of days ago. I hooked the 1.0-5.0v output to the rear O2 sensor input of my ECU (DSMLink will log it) and the 0.0-1.0v output to the front O2 sensor input at the ECU in place of the stock O2 sensor. Pretty simple installation. That's the good news.

Bad news. It only took me a couple of minutes drive time to figure out it won't work this way. The car started fine & idled fine (lean @ 16.5-17.5:1 a/f ratio). But trying to drive it was another story. Once I started driving the car the ECU started to go lean very quickly and very badly (19.4:1 on the UEGO) to the point were it lost all power. DSMLink was showing .40v at the front O2 sensor input and my fuel trims were going way lean. I re-checked everything to make sure it was hooked up correctly and it was. So yesterday I called AEM tech and asked them about it. They told me .40v is really lean on the low-band output. I told them I agree, but .40v is not lean for a stock style ECU as .50v is stoich (14.7:1). This is not a very good "mimic" of a stock style O2 sensor. The ECU is looking for a lower number to see lean mixtures. AEM tech didn't have an answer for me on this. I guess most people buy the UEGO controller to hook to a stand-alone system.

So today I put the stock O2 sensor back into place and had an exhaust shop weld in the add-on bung into my exhaust right after my flex-joint at the rear of the engine where I mounted the wide-band sensor. All my fuel trims lined back up correctly. The UEGO shows 14.5-15.2:1 a/f ratio while idling and cruising with the stock O2 senor controlling things. I did go up on boost also and found my WOT ratios to be 10.5-10.8:1 without me changing anything. So my fuel trims were pretty close, but now I know for sure. So now I can at least have a real-time display of my a/f ratio and log it.

So for a "heads up" to everybody, I can't say for sure if the FJO, PLX, etc. wide-bands do a better job of trying to "mimic" a stock O2, but they will need to if you are trying to do what I was trying to do. Other than that, everything is great.