BMW F800GS engine tuning

Discussion in 'Parallel Universe' started by DakarBlues, Dec 17, 2009.

  1. Bushwhacker

    Bushwhacker Dirt, Sweat & Gears

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    No such thing as a perfect air/fuel ratio.

    14.7:1 is the ratio that has a Lambda of 1. That means you thoeretically have exactly enough air molecules to burn all the gasoline molecules. That is what the EPA thinks is perfect because it produces the least emissions.

    A slightly lean mixture - 15.4/1 - generally gives the best fuel economy.

    A slightly rich mixture - 12.6/1 - generally gives the best HP.

    I have read that a bit leaner - 13/1 - produces the most torque.

    Also leaner engines run hotter and therefore are more prone to pre-ignition, ie knocking.

    Richer mixtures run cooler and most likely add to engine life.

    Also a flat air/fuel curve is not necessarily the best although it does give the smoothest, most predictable power delivery, however it would seem to me that an Air/fuel curve that starts out at about 13 or a bit higher/1 and then decreases to about 12.5/1 over the RPM range would give the best torque in the lower RPMs and the best power in the upper range. This would cost you in fuel economy but I am willing to give up a bit of economy for a bit more power.

    Plus this entire discussion is for pure gasoline/air ratios. Gasoline additives change the analysis and every vehicle has to be tuned on a dyno with the fuel it is going to run to obtain optimum results.

    And finally, all of this is for normally aspirated engines and forced air induction engines (turbocharged) should be run richer still for both optimum power and engine life.

    JMHO - YMMV
    #61
  2. The Griz

    The Griz Long timer

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    Well, I can tell you right now that if I had tuned my KLR to 15:1 or higher I would have been seriously overheating and damaging many things. When I was going through the paces with tuning that bike, I remember hitting 15:1 and being far to lean on a test run. I got home, pulled into the garage, got off the bike, and noticed my header was glowing bright orange. 15:1 or higher for the KLR for any extended period of time: NO GOOD.

    Read my previous post. You're basically echoing exactly what said. We've already been through this in this thread.
    #62
  3. LukasM

    LukasM Long timer

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    Griz,

    All you ever wanted to "achieve" was 14.7 and now 15:1 would seriously overheat and damage the bike. :baldy

    If you really have still not understood it, you don't tune for ONE specific number, and 14.7:1 is not known and has been known for decades to be the perfect air/fuel mixture for gasoline-burning engines - unless you are talking about emissions.

    Like I said from the beginning, you tune for load/throttle position, going from slightly lean at cruising RPMs (where it will not damage anything) to rich under full load (to produce max power and protect the engine from detonation and overheating).

    Now please stop posting more BS, or at least read through the previous replys as we have been through all this already.
    #63
  4. The Griz

    The Griz Long timer

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    OMFG Lukas, seriously. You're not reading what I'm posting. You're the classic case of someone who constantly talks but doesn't listen.... always thinking about what you're going to say next instead of listening to what the person in front of you is actually saying.

    I have NEVER said that I EVER want to achieve 14.7:1 at all times under all throttle positions and under all loads and conditions. We all "shoot for" 14.7:1 is all I was saying. So yes, we've been through this. You're the one who's not getting it.:deal

    Mods, please nuke this thread.:becca:baldy
    #64
  5. ride2little

    ride2little MoveAlongNothingHere

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    so, with all of this back and forth banter...is there a solution?

    IMO, open up the exhaust, the intake doesn't appear to be a restriction and a re-map to enrichen it up a bit.

    In summary.
    Exhaust can
    header (optional)
    Power Commander (or equivalent)
    tune.

    No?
    :*sip*
    #65
  6. LukasM

    LukasM Long timer

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    You are so full of it and still don't see it. Nobody except you (and the manufacturers for emissions reasons) is aiming for 14.7.

    Because, again, what you said below is BS:



    Thats a good plan. The key here is the PC to richen up the mixture if you open up intake and exhaust.
    #66
  7. ride2little

    ride2little MoveAlongNothingHere

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    Oh...additionally, I've done this on all other bikes I've owned (usually a re-jet). And it does NOT cause your MPG to suffer. Rather it usually improved it.
    Your motor works more efficiently. It actually works less for the same amount performance. The only issue is that once you see your motor perk up (improved throttle response), you may get into the throttle more which WILL cause the MPG to suffer.
    #67
  8. The Griz

    The Griz Long timer

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    I have to post it again I guess:

    I have NEVER said that I EVER want to achieve 14.7:1 at all times under all throttle positions and under all loads and conditions. We all "shoot for" 14.7:1 is all I was saying. So yes, we've been through this.

    Did you hear this time?:scratch

    14.7:1 is completely safe: on an engine running at a constant RPM under constant atmospheric conditions and loads. I never said that it is safe for a motorcycle at all times under all loads and conditions. I said it's what we "shoot for".

    And, yes, contradicting the 14.7:1 stoichiometric ratio is going against 80+ years of hard scientific evidence.
    #68
  9. ride2little

    ride2little MoveAlongNothingHere

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    This thread has since lost all of it's usefulness.
    Can you folks please take this debate off-line? Or at least delete your back and forth?

    Thanks.
    #69
  10. The Griz

    The Griz Long timer

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  11. The Griz

    The Griz Long timer

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    Good call.:thumb
    #71
  12. The Griz

    The Griz Long timer

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    +1 This was my exact result after re-jetting my KLR650.
    #72
  13. EmmettC

    EmmettC n00b

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    I hope this thread is still being used.

    I had my bike run on a dyno the other day, it's got a remus exhaust system and an Arrow can. It's making 82.51 HP.

    The guy who runs the tuning shop (in Edinburgh) reckons it running very rich at full throttle, and very lean while cruising. I've ordered a PC so he can tidy up the fueling, I'm not looking for more power, I just want it to run well.

    I'm a little worried about the fuel consumption increasing, as the tank is soooo small it really needs to be very frugal to be any use.

    I'll update once the tuning work has been done. hopefully more torque, the same or better fuel consumtion, and If there's more power too, I won't complain.
    #73
  14. Gangplank

    Gangplank Advenchaintourer

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    Yes!! Really happy someone decided to take this one. I've been thnking about it myself but don't have the time or a good tuner withing 4.5 hrs drive. Let us know the results. I have a similar set up to you with the Leo V. pipe so might be able to apply your results.
    #74
  15. ebrabaek

    ebrabaek Long timer

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    You might wan`t to look into Dynojets autotune box along with the PC. It will allow you and your bike to tune outside the dyno....and makes for a awesome user friendly package, that you can work yourself.

    :thumb:thumb

    Erling
    #75
  16. c5babe

    c5babe Been here awhile

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    I have 40,000 miles on my F-800. My trusty DR650 is my adventure bike of choice.
    #76
  17. itsatdm

    itsatdm Long timer

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    Before I let a tuner start playing with the settings on this bike I would read the related threads by Poolside. It pertains to the 1200 GS but it uses the very same system on the F800. http://www.advrider.com/forums/showthread.php?t=638412

    First of all the system is complex and with overlapping functions. Secondly I think it is hardwired or imprinted so the basic function of the software cannot be changed. My laymans understanding, is the basic software is programed so that it responds to sensors elsewhere in the system. That include, air temp sensor, TPS position, altitude and/or oil temp sensors, and finally an oxygen sensor.

    You are right about the bike running lean, and the Oxygen sensor will attempt to maintain what ever value BMW programed into the software. Probably 14.7 A/F. What A/F did your tuner feel was lean at steady state?

    When the ECU detects a signal from the sensors that indicate a need for a different ratio it will react and increase fuel flow to adjust to condition.
    For instance twist the throttle will instruct a richer fuel ratio. You did not say what ratio the tuner is seeing at W/O throttle, but that undoubtedly is what he is seeing. But it is temporary, once load or throttle is reduced the A/F ratio falls back to normal, because eventually the Oxy sensors over rides all other sensors.

    There are ways to trick those sensors into giving modified readings to the ECU. That is what the Booster Plug is doing to the temp sensor. But I do not think you can do anything to the base map except remove and replace with something else and probably remove the oxy sensor as well.
    #77
  18. jscottyk

    jscottyk Been here awhile

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    itsatdm, did you get one of the first one hundred IICE Air units?
    #78
  19. itsatdm

    itsatdm Long timer

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    No, I have the Accelerator module installed for some months. I certainly would have considered it, except for the bad timing.

    Sounds like the same principal, but with some added adjustability/
    #79
  20. mapa63

    mapa63 Bikerider

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    Hi guys!

    Has anyone here actually used a Power Commander V with or without Autotune? I'm primarily interested in making the bike less snatchy. Well, maybe some extra torque at low revs would be nice. Have changed the front sprocket to one tooth smaller.

    I've read some of Poolsides write-ups and if I understand it correctly a PCV is a bad idea for the F8GS?

    Best regards,
    thankful for any info
    #80