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Thread: Richer fuel map for a standard XB

  1. #11
    Senior Member Cooter's Avatar
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    But ReadyXB is right. A stock bike in good shape shouldn't misfire.

    The old wives tale of a vehicle meant to run 'lean' for the EPA has always been hogwash. An engine running even slightly lean will have terribly high NOx and Hydrocarbon (HC) emissions, both of which are scrutinized by the emissions police. MFG's don't shoot for lean, they shoot for stoic (14.7:1 in CL). 14.7:1 is not lean, it is efficient and clean burning. An engine running even slightly rich in CL will have higher Carbon Monoxide (CO, also scrutinized) but will have better throttle response because when the engine needs the extra gas, *it's already there immediately without waiting for the ECM/injectors to compensate.

    You will never see more power in closed loop because, by definition, closed loop is part throttle, cruise condition. Keep your AFR targets in CL at 14.7.

    AFR targets in OL are a different story. MFG's are not able to dump mass amounts of fuel into the engine (causing high CO) for acceleration because of the EPA. There LOTS of opinions on what targets to use, but around 13:1 is typically accepted for V-twin performance.

    *this may be why you think it runs better with the AFV locked at 108%. The rich cylinder has extra (normally wasted out the tail pipe when cruising) fuel ready to be burned when you blip the throttle.

    I'd still check the intake seals though.

  2. #12
    Quote Originally Posted by Cooter View Post
    Hey Gunter: Sorry for the side track, but just confirming the AFV is a ECM "global map adjustment", but for OL only?

    Where EGO (WEGO) is for CL only?
    AFV is applied in open loop operation only, whereas EGO correction is applied in closed loop only.
    AFV is also the reason, snake oil like the mentioned devices will not work. Fuel is added because of a fake temperature signal, EGO corr. removes fuel in CL to get a stoich mixture, AFV is dropping because of EGO, fuel is removed in OL, and you are where you were before. This is also the case for each ECU manufactured the last 15, maybe even 20, years. Better donate for a copy of EcmSpy, because this is known to work.

    Stumble at very low engine speeds seems almost always a timing problem, and take into account that all "Idle ..." settings get active once engine speed is below the Idle Max. Engine Speed.

  3. #13
    Senior Member Cooter's Avatar
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    Thanks Gunter for the clarification, and nice to hear from you. It's what I thought, but in searching the ECMSpy instructions I couldn't find it spelled out precisely that way.

    Another question if you don't mind: What are your personal favorite AFR targets for WOT on a XB? Are they the same for 9 vs. 12? Mods? I feel if I get good enough at tuning Stella, when it's time for a 1250 kit I could start with it's current tune and datalog with the same WB O2 I have to make a good 1250 tune for her.


    Sorry OP for the hi-jack and whole-heartedly agree about the sensor mod trick devices.

  4. #14
    I never tuned the WOT part of a map using a WB O2 sensor, as I do not have access to an EC dyno, and anything else would be a waste of time, budget and fuel.

  5. #15
    Senior Member Cooter's Avatar
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    I have a great dyno guy close by, but that adds up $$ so I'll WB, OL tune on a 3 mile arrow straight road (with only one entrance ramp) near me to get close, then finalize quickly with about an hour of dyno time when I finally get the chance.
    I'm only tuning for good safe mixture (not HP), so it works for me.
    At 13:0 OL targets, theres no black smoke, I haven't had an issue fouling anything, and can't seem to get any more power when I'm actually on a dyno. Thought you might have a different experience.

    Thanks again, your wisdom is appreciated

  6. #16
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    Quote Originally Posted by Cooter View Post
    Sorry OP for the hi-jack and whole-heartedly agree about the sensor mod trick devices.
    No problem Cooter - when you heavyweights talk, we all learn. I wasn't endorsing the sensor mod trick devices, just illustrating that there are a lot of people who find the emission regulation compliant fuel maps unsatisfactory, as do I, if it runs nicer when richer. Even you said you'd had good results locking the AFV up to 115%.
    I've a question for Gunter re his comment about "Limiting AFV has nothing to do with closed loop operations" and the ECMspy tuning doc '5.1.3.2 Closed Loop Learn...The fuel (in CLL) is metered the same as in the Closed Loop region, except after 23 iterations of a difference between EGO and AFV, the AFV is reset to equal the EGO correction.'
    Until now I understood that when locking the AFV the closed loop function (of reducing AFR to stoich at cruise) was also effectively disabled. Is that not true? Does the fuelling in the closed loop area still respond to the EGO sensor and come back to stoich, while just being unable to alter the AFV after the 23 iterations?

  7. #17
    Senior Member Chicknstripn's Avatar
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    Only contribution I’ll make to this thread is that you first insure that everything is mechanically sound with the bike before you start messing with the fuel maps. Check all your grounds, do the dedicated battery to coil ground, check your plug wires, check your plugs, insure you don’t have an intake leak, make sure your TPS is set correctly... and I’m sure there are other checks that I’m missing that will be mentioned. The point is, if you don’t make sure the bike is in perfect mechanical order, changing the fuel maps will only compound any running issues.

  8. #18
    Quote Originally Posted by John Vreede View Post
    Until now I understood that when locking the AFV the closed loop function (of reducing AFR to stoich at cruise) was also effectively disabled.
    This is not the case. AFV is always limited, and always checked against its threshold values.

  9. #19
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    Thanks Gunter.
    So does this also mean that, even when both upper and lower AFV limits are the same, that the ECM will still drive the fueling in the closed loop area toward stoichiometric - jv


    Last edited by John Vreede; 06-17-2018 at 10:01 PM. Reason: Didn't understand.

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