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Thread: AFV Questions

  1. #1
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    AFV Questions

    Ok, so in the process of researching exhausts I started reading about AFV values and how it will fluctuate depending on altitude and other factors with fuel, injectors, seals, etc. I checked my afv last week and it was at a 89.2%. Now I know you want it as close to 100 as possible and that if your within 10 either way you should be good. Wondering if I change mine to 100 and burn(save) the change A) will it screw anything up on ECMSPY in terms of my maps etc. I have the stock saved, thats one of the first things I did. and B) will the bike run any different but then revert back to what its used to or will it relearn for this altitude and change for better or worse? Ive searched and read through all the AFV stuff I could find on the forum and nothing really answered these type of questions. And also so I understand below 100 is rich and above is lean? Thank you.

  2. #2
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    A) Changing the AFV will not alter the fuel or timing maps.
    B) Unless you prevent the ECM from changing AFV, you can reset it to 100 but the ECM will adjust it back to whatever value is needed.

    And it can happen quickly.
    For the section highlighted in purple, AFV dropped from 89.7 to 76.8 in just 7 seconds.
    AFV_Step_.jpg

  3. #3
    Senior Member Cooter's Avatar
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    You didn't mention it so, does the bike run ok?

    No? Find out the CAUSE. It's important to understand that AFV is a RESULT. It is never the CAUSE.
    Yes? IMO, just leave it alone and go for a ride

    AFV is the RESULT of the ECM adjusting to a neutral (stoic) spot, according to the info the ECM is receiving. Forcing the AFV to be somewhere can be a diagnostic test, BUT it is a dangerous game to play. You are dis-allowing the ECM to adjust, and that can be catastrophic

  4. #4
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    Quote Originally Posted by Cooter View Post
    You didn't mention it so, does the bike run ok?

    No? Find out the CAUSE. It's important to understand that AFV is a RESULT. It is never the CAUSE.
    Yes? IMO, just leave it alone and go for a ride

    AFV is the RESULT of the ECM adjusting to a neutral (stoic) spot, according to the info the ECM is receiving. Forcing the AFV to be somewhere can be a diagnostic test, BUT it is a dangerous game to play. You are dis-allowing the ECM to adjust, and that can be catastrophic
    Yes bike runs fine. And thats why I have not touched anything because A) it runs fine and B) I have no clue what Im doing with ECMspy and dont want to mess anything up. But bike is pretty much done for the season so im starting to pack it up. Ill be doing some small things over the winter.

  5. #5
    Senior Member Cooter's Avatar
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    Whats "winter"?






    It's perfectly fine to mess around with it. Just make sure you save your spot, Morty It's honestly a very simple process, if you understand tuning in the first place.

    And that is the problem. It's not a subject where truth equals democracy so the most FaceBook replies win You need to read the information from the source. Any question you have should be asking for definition, not solution.

    Don't worry the info is easily found and free, it's just that no one does it. They run to the computer and post "HEEELLLPPPP!!!! I was messing with my ECM and now my bike won't start!!!"
    -Replace your battery-Check your grounds-Does it have gas? LOL.

  6. #6
    Senior Member mriulvr's Avatar
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    Quote Originally Posted by Cooter View Post
    Whats "winter"?






    It's perfectly fine to mess around with it. Just make sure you save your spot, Morty It's honestly a very simple process, if you understand tuning in the first place.

    And that is the problem. It's not a subject where truth equals democracy so the most FaceBook replies win You need to read the information from the source. Any question you have should be asking for definition, not solution.

    Don't worry the info is easily found and free, it's just that no one does it. They run to the computer and post "HEEELLLPPPP!!!! I was messing with my ECM and now my bike won't start!!!"
    -Replace your battery-Check your grounds-Does it have gas? LOL.
    ^^^^Words of wisdom. Having gone through the process of tuning my 04 XB12S (which entailed a lot of reading, rereading, and asking questions to the point that I thought I got it), I still made mistakes along the way. Understanding the process, how the ECM works, what you are wanting to accomplish, knowing your setup, understand the data, and making sure you don’t have other issues that need fixed first are a must. Having your stock EEPROM and maps to reflash was critical. I also saved every revised map by date so I could revert to one if something went wonky.

    I learned a lot in the process but got tired of the running down the rabbit hole and just wanted to enjoy riding and caring for her. In the end I ordered an EEPROM for my Buell with a Hawk exhaust, flashed it, and been happy since.

    You can get good EEPROMs for most Buells and exhaust setups at reasonable prices from people who know their stuff that will work great. Unless you just have to have those couple extra horsepower or are an obsessive tinkerer,

  7. #7
    Senior Member Cooter's Avatar
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    I hear that exact story so often ^^^^, and you bring up very important points. Especially to making sure the bike is in VERY good running condition BEFORE ANY ATTEMPT to tune it.

    It's fun to 'tinker', especially when its ostensibly free... and you can learn a lot! But is that why you got the Buell? I prefer riding mine

  8. #8
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    Quote Originally Posted by mriulvr View Post
    ^^^^Words of wisdom. Having gone through the process of tuning my 04 XB12S (which entailed a lot of reading, rereading, and asking questions to the point that I thought I got it), I still made mistakes along the way. Understanding the process, how the ECM works, what you are wanting to accomplish, knowing your setup, understand the data, and making sure you don’t have other issues that need fixed first are a must. Having your stock EEPROM and maps to reflash was critical. I also saved every revised map by date so I could revert to one if something went wonky.

    I learned a lot in the process but got tired of the running down the rabbit hole and just wanted to enjoy riding and caring for her. In the end I ordered an EEPROM for my Buell with a Hawk exhaust, flashed it, and been happy since.

    You can get good EEPROMs for most Buells and exhaust setups at reasonable prices from people who know their stuff that will work great. Unless you just have to have those couple extra horsepower or are an obsessive tinkerer,
    Oh ya im not going to tinker with the ECM at all. Ill be getting an exhaust and putting that on over winter and im just gonna get a new ECM from IDS and hopefully thats good enough. I have a headlight project ill be doing also. Just double checking the bike and all its nooks and crannys is what Ill be doing.

  9. #9
    Senior Member BuellyBagger's Avatar
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    Ok, imma thread jack a bit... on subject though. So I've got a 20006 xb12x 11k miles k&n, breather mod, "Swiss cheesed" airbox, and was running a modified stock muffler with a race tune. I bought the xb-sg muffler from rev-mo and when doing that checked my AFV and found it to be 109. Rev-mo guy sent me a closed loop tune, unlike his normal tunes because he was concerned that my afv was too high and I may have a mechanical issue(I might have that backwards, I don't wanna get open and closed loop turned around, but he sent me one that allows the ecm to change the afv) so before installing his tune blindly I installed the new muffler and took it for a few rides. The bike runs amazingly! A good bit better than with the previous muffler. Then after a couple of rides I rechecked the afv and it's 119... absolutely no rideablitly issues that would indicate an intake leak or that bike is lacking in fuel delivery. So, what's the next play? Try his tune? Ride it, since it runs great? I get that it's obviously trying to richen itself up and don't want it to end up too lean.

    (I did read cooters suggestions to just ride it if it runs well earlier in the thread, but wanted to put my situation out there)
    Last edited by BuellyBagger; 11-12-2021 at 02:21 AM.

  10. #10
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    Winter is the season you miss when living in Florida or on the wrong coast.



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