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Thread: High AFV on XB12SS Long

  1. #1

    High AFV on XB12SS Long

    A mate brought his 2006 XB12SS Long to my place, and we ran ECMDroid via Buelltooth on it to see what it was doing.
    Apart from a K&N air filter, it is a bog standard Japanese spec bike (BUEIC ECM), still running the muffler valve, with 12000mi on it.
    It runs very well, subjectively engine power, smoothness and ridability feel very like my richen-up Uly.
    However the data channels show (on live data when idling):
    RPM 1237
    TPD 6.0deg
    EGO correction 126.9%
    AFV 126.9%
    The AFV and EGO corr. had the same values after he came in from a 20mi ride as well.
    The idle rpm is a bit high and I suppose that would bring the TPD down to a reasonable number if adjusted, but my query is with the AFV
    From this number I gather the ECM is richening the fueling for a sensed lean condition, presumably the K&N airfilter.
    My questions are:
    Is this how high you'd expect the AFV to go on just an K&N airfilter change?
    Or is there something else going on?
    Any issue with leaving it like this?
    Thx - jv
    Last edited by John Vreede; 10-18-2018 at 04:49 AM.

  2. #2
    Senior Member Cooter's Avatar
    Join Date
    Dec 2012
    Crawling up your skirt
    Curious. Did you get the "Japanese spec" because of the VIN#? The firmware version won't matter as long as the tune matches if you change it. Different firmware versions actually store the fuel map in different places in the memory. Although ECMDroid (and later versions of ECMSpy) won't allow you to download the wrong firmware version map, TunerPro will and that will definitely cause you problems.

    I would not recommend changing or tweaking the ECM until you diagnose the bike much further. Tweaking the ECM now would just cover up the problem.

    I don't believe just adding a K&N filter would cause the ECM to enrichen the entire fuel map almost 30%! But leaking intake seals would. O2 sensor maybe, clogged fuel filter or injectors, weak fuel pump, anything restricting fuel flow. The basics really. Theres no way to diagnose this over the web, anyone guessing is just guessing. You'll have to get dirty. Post up what you find!

  3. #3
    Senior Member Cooter's Avatar
    Join Date
    Dec 2012
    Crawling up your skirt
    Leave it like that? How far do you want to crank up the radio so you don't hear the brakes squeak? lol.

    An issue I see with leaving it like that is the ECM will run out of correction room and eventually just go lean (bad). What are the AFV limits set at now?

    And it's seems way past what a well running bike would need to correct. IMO, I'm ok with AFV at 95-105 and consider that a well running bike (1st) with the right tune in it (2nd).

    In my experience

  4. #4
    Thanks Cooter
    We get a lot of used Japanese vehicles in NZ and this is just one of those (they drive on the RHS of the road like us - not that it matters with a bike). The VIN and ECM designation just confirmed what we already knew.
    We didn't try any tuning when we saw the AFV%.
    I didn't think that 30% richer would be just the result of a K&N filter, so nice to have that confirmation. The AFV limits are set at 150% max and 60% min. The 'AFV setting' under ECM Parameters is reading 126.9%, but that just reflects the correction the ECM is making doesn't it?
    The bike runs VERY nicely now, with good power and throttle response. Wouldn't a leaking inlet seal etc cause it to run poorly? Or does the AFV cover a leaking seal? (the Active Tests runs the fuel pump for exactly 30sec just like it does on my Uly so don't think that's a problem (unless 30sec is too long - it does seem more than long enough to test the pump?) - jv

  5. #5
    Junior Member
    Join Date
    Jul 2016
    In addition to a leaky intake as Cooter says, it might be worth checking that the rubber air intake boot is properly sealed against the airbox baseplate, it has two "lips" which should go on either side of the baseplate hole, easy to forget if in a hurry - don't ask me how i know.
    Results in a High AFV and a very lively bike.

  6. #6
    The airbox inlet (be it the hole through the frame or the newer version of the airbox lid) is not that limited, that an additional incoming air flow will have a great impact in fuelling. Definitely not in LCL operations. At WOT and high RPM (7000+) old style airboxes might show rising AFV one step (appr. 5%) caused by to OLL in this case, which will disappear when reaching LCL again. As a side note: I will never understand, how any runtime value recorded while idling will have any significance when riding. Idle is a completely different setup.

  7. #7
    Thanks Taz and Gunter.
    Was a completely new bike to me so I just recorded what values were there and it was idling at the time, which does give info on the TPS.
    That's why I sent him out on a 20mi run to see what the values were when he came back and they were still very high AFV.
    Now what to do?
    Should have put the stock new air filter off my bike into it to answer my own first question. Will do it, but pretty confident the AFV will still be high.
    Checking for air intake leaks seem the logical first step
    It has the slight misfire/hiccup that my bike showed, so he's going to bond the earth wires. Unlikely that's contributing but we'll see. (As an aside: there doesn't appear to be any collection of earth wires at the headstock at all on this bike - not under the torx screw like my Uly (which is there but holding nothing), nor under the bolts through the headstock casting that retain the plastic flashing over the wiring loom, nor to either triple clamp. The earth wires just seem to disappear into the wiring loom so I'm guessing they're earthed back at the subframe. Seems strange that the Japanese models would be different like that? - jv

  8. #8
    Senior Member
    Join Date
    Mar 2015
    Phoenix, AZ
    Quote Originally Posted by John Vreede View Post
    Now what to do?

    Checking for air intake leaks seem the logical first step
    I'd start here.

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