A/F Learning and Knock Weather related?
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This is a discussion on A/F Learning and Knock Weather related? within the Tuning: Electronic Engine Management forums, part of the Tech & Modifying & General Repairs category; I've been using the Cobb AP to check the values while cruising / commuting. I noticed that my A/F Learning ...

  1. #1
    Registered User
    Join Date
    Mar 2014
    Las Vegas

    A/F Learning and Knock Weather related?

    I've been using the Cobb AP to check the values while cruising / commuting. I noticed that my A/F Learning 1 would shoot up to +7.81 when idle and back down to +7.03 and sometimes +6.25 and would go back down to normal values within a +1-3 range when on the throttle. My car is a 2013 WRX with 11,500 miles. No engine mods besides Stage 1 ACN91 and a turbo blanket.

    I live in Las Vegas and the weather has been 82 degrees so Summer is just around the corner, not to mention it can get really dusty around my area commuting back home. I already cleaned the MAF sensor with CRC, and reset the ECU, so the values look much better than before, but throttle response is a bit delayed. No rough idles, though. I think the ECU is still learning. I just filled up on a full tank of Shell V-Power before the reset and MAF cleaning.

    I also noticed with an increase of the A/F Ratio I seem to be getting FBKC sometimes hitting as high as -6, but not as common as -1.4 or -2.8, and it ramps back down to 0 as I go WOT. I'm thinking it's just false / phantom knock or something is loose. I can't seem to recreate the knock as it seems to be random. FBKC seems to be more active in 5th gear when giving it more gas on the highway (about 2500-4000RPM @ 70-80mph), but not WOT, but then I start seeing -1.4 in FBKL. I have never seen FBKL exceed -1.4.

    So would hot weather cause the A/F values and knock to be more active? It can also get real windy and dusty. The WRX hates Las Vegas weather. Cold winter weather with the same OTS tune, my car was running amazing, no knock at all and A/F was always at -+5%. Now that summer is coming, value are getting very high. Not sure what to think of it.

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  3. #2
    Moderator Donkey's Avatar
    Join Date
    Apr 2005
    Da boonies,Va
    I Support ClubWRX
    The answer is yes. It's basic science. Hotter weather is not as dense as cold weather right? Also hotter weather means the intercooler is less efficient yes? The ECU does use intake air temps to help calculate fuel and timing.
    Resident Adviser @ WTF Tuning, LLC
    2002 FORESTER S
    1998 FORESTER S

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