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Thread: Post Tuning Settings

  1. #1
    Senior Member mriulvr's Avatar
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    First, sorry for the long post but wanted to make sure I was communicating my questions clearly and completely. I finished tuning my 04 XB12S, K&N air filter, NGK plugs, breather reroute, Hawk exhaust, Redline 10W-60 in both holes with an LC-2 wideband O2 sensor on rear, no sensor on front, and MLC. Even after reading extensively on the tuning process, I need the collective wisdom of informed forum members for two topics.

    1. I have read various opinions on adjusting the front fuel map based on rear map tune. Add 2, 3,... to the cells in the rear for the front being the most common. This just does not seem to jive for me. Adding 3 to a cell of 20 is a 15% change while adding 3 to a cell of 200 is a 1.5% change. The following is what I found when I compared the difference of the front cylinder race fuel map to the rear race cylinder fuel map.



    As you can see the cells in the front cylinder are anywhere from 30 less than the rear to 30 greater than the rear. This seems to raise some questions about the "add 3" rule.

    I also found the front race fuel map cells as a percentage of the rear race fuel map cells, see below.



    The percentage increase from rear to front varies from 83% to 155%. Also, just to address the add 3 rule, an increase of 3 at 10 TPS and 2400 RPM results in a 9% increase while the 3 point increase at 80 TPS and 5000 RPM is a 2% increase.

    I have been adjusting the front using the percentages in the second table for my tune as the percent difference makes more sense to me than the add 3 rule. What I am curious about is what these comparisons (difference and percentage) look like for those of you who have done your tune with a wideband O2 sensor on both front and rear. I would be interested to see if either of these comparisons come close to what tuning both maps produces.

    So, if you have done tuned both front and rear with a wideband O2 and could post these two comparisons for your tuned maps I would appreciate it or if you PM me your front and rear, I will do the comparisons and post them for anyone else interested.

    2. This one is simpler. Once you are done with your tuning and set the wideband O2 sensor to emulate a narrowband O2 sensor do you use the same voltages for rich and lean that are in the stock EMC and if so what AFV values do these voltages correspond to? If you emulate with a different low and high voltage do you need to set the rich and lean voltages in the EMC to these same voltages? I am keeping the stoich 14.7 voltage the same as stock so just need to figure out how to be sure the LC-2 and EMC are looking at voltages above and below the same way.

  2. #2
    Senior Member mriulvr's Avatar
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    MLV (Megalog Viewer) not MLC.

  3. #3
    Senior Member AZmidget91's Avatar
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    I know it sucks, but the best option is to put a o2 bung in the front and do some tuning with that now. I have the same opinion about add 2-3. In theory it makes sense, but just can't be right. If you have a wideband, I think it would be worth it to move it to the front and do some more datalogging.

    As for the narrow band settings, you need to configure one of the outputs of the LC1 to be narrowband (usually on of the outputs is already set up this way) But just make sure the LC1 and your ECU have the same settings, I would use the stock Buell settings though. (been a couple years since I set up a LC1 so its a little fuzzy)

  4. #4
    Senior Member mriulvr's Avatar
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    Thanks AZmidget91

    I agree that the best option is to tune the front and back together. That is on the "eventually when I have the time" to do list. I have a nephew that is a welder who could install the bung for free but he is in another state. Have also been considering new headers and would make sense to do it when I installed them. In the meantime, I was curious what the results were for those who have already done this, if there is some consistency in the rear to front maps, and if they are close to the percentage differences for the race maps.

    I have the LC2 set to emulate narrowband, can't remember off the top of my head what the voltages and AFR ratios I used were, and got to thinking about this on my ride in to work this morning. Setting the lean and rich voltages to be the same on the LC2 and ECM is easy but I wasn't sure what the AFR values the ECM voltages correspond to so that they also match the settings in the LC2.

  5. #5
    Senior Member mriulvr's Avatar
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    Here is what I have the LC2 narrowband set at.



    To clarify my second question, if I set my ECM rich and lean voltages to .88 and .100 as in LC2 will the ECM interpret these voltages as corresponding to the 14.45 and 14.95 AFR's and adjust accordingly?

  6. #6
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    leave ecm voltages stock, and skew WB output to get a 14:1 in any data acquired cells. or whatever ratio you tuned to.


    dont forget the slope of NB to WB is negative

  7. #7
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    You're thinking about it too much...unless you tune the front cylinder separately, the +3 method works fine. Also...there really is no need to run a richer closed loop. Hell, I run mine between 14.7-15:3:1 on my bike. No pinging here...110+℉ in Vegas. 45mpg average. I tune with a wideband and still use the stock narrow band for standard corrections.

  8. #8
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    i ran mine for 4 years in vegas tuned to below stoich with the same mpg.

    fan never really came on. but thats not a good metric.


    i also have customized my ignition timing. however, for his purpose, the fundamental of matching the output from the LC to the ECM based on his target tune remains relevant.

  9. #9
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    adding a fixed number instead of a percentage multiplier to the front fuel i believe stems from the amount of time the front cylinder has to charge the intake tract. it gets 405 degrees of rotation, meanwhile the intake is filling up with air.

  10. #10
    Senior Member mriulvr's Avatar
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    adding a fixed number instead of a percentage multiplier to the front fuel i believe stems from the amount of time the front cylinder has to charge the intake tract.* it gets 405 degrees of rotation, meanwhile the intake is filling up with air.
    So why would the race map not reflect this? There are cells in the front cylinder race fuel map that are actually lower than the rear cylinder fuel map. Not arguing as you are WAY more in the know about this than I am, have been doing this for a long time, and have been very helpful with the tuning process. Just curious and still wondering about how front and rear compare for those who have tuned both with a wideband O2 sensor and if that would help make a better adjustment for front based on rear tune.

    This also makes me wonder if the AFRbins for front and rear should the same when I finally get around to welding the bung to the front and tuning both. My tune has idle at 13.2:1 open loop at 14.7:1 and decreases to 13.2 for wide open throttle.



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