Quote:
Originally Posted by theadmiral976
Thanks for the info. To add details to the discussion for future reference, I have only moved my O2 sensors once, when I installed my OFH over a year ago. They are definitely not cross-threaded, nor did I hit the sensors against the bung during install. I'm currently at 42k miles, with about 20k miles on the OFH. I monitor my trims pretty regularly and haven't noticed the commanded AFR dropping before the ~1.5 hour mark of constant RPM cruising on the highway. I regularly take 5-hour constant RPM trips, so perhaps if others aren't doing this, they would never notice the problem. Still not really sure how to mechanically/physically explain the timing, though (e.g. why it takes upwards of 90 minutes to see an effect).
I never saw this cAFR drop prior to installing the uncatted header (I ran OFT Stage 1 maps for about 12k miles prior to installing the OFH). Good to know that other uncatted headers seems to be causing the same issue.
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That's funny you said that because I didn't start seeing this until I ran the Stage 2OFH tunes that were just released. Or maybe I just never paid too much attention to my AFR running the previous tunes including E85 tunes and I'm just seeing this for the first time. In stop-in-go traffic this never happens to me. but if I'm constantly on the throttle at 70mph for more than 30 minutes the car will creep slowly until it's stuck in open loop.
And like OP stated, it may be related to the catless design allowing more heat and deposits to the secondary O2. Unlike the primary O2, It probably can't absorb heat or fails if it's exposed too long to the same heat the primary O2 sees. For this reason I didn't want to spend money on a new secondary O2 and have it fail over time prematurely. I ended up disabling my LTFT and ignoring secondary O2 feedback. I tested tonight and it's working flawlessly except I think I lost some power because if i'm below the closed loop threshold the car will not add fuel in open loop to any rpms until I actually hit close loop. Feels like a lack of throttle response under normal driving but once I see closed loop engaged power kicks in. But we'll see as the car relearns itself after a few days.