KTM 990 Idle Speed Control Stepper Motor Operation

Discussion in 'Dakar champion (950/990)' started by BillyD, Jul 6, 2010.

  1. chevtech

    chevtech Long timer

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    If the throttle plates are always sitting on the SM rather than the idle screw, setting
    the TPS voltage at "closed throttle" would be pointless, as the stepper motor can change its position CONSTANTLY. It would have to be done when the system is sitting on the idle screw ONLY.

    Are peeps checking that it is only on the idle screw prior to adjusting TPS voltage?

    Just a thought...


    Todd
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  2. rider911

    rider911 Shortcut Navigator

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    I don't believe so, the SM is adjusting the TPS. The TPS is determining the mixture and timing.
    The SM is driven by the ECU which is using the RPM reading and comparing it to to the idle speed written into the map (which you can adjust via tuneECU)
  3. Themastermike

    Themastermike Think you caught me in a coma Supporter

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    That is the crazy part, with all the write ups out there I never have seen the how to on schlepper motor replacement, just adjust to the target voltage, then try try again

    Sent from my SCH-I535 using Tapatalk
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  4. Mr Head

    Mr Head Adventure Hippie Supporter

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    Motors don’t tell anything to do anything. They are actuators. The TPS is a sensor. It changes its voltage output relative to rotation. The ECU is the controller. Hence the name.


    Sent from my iPhone using Tapatalk
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  5. gefr

    gefr Life is a trip

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    So s/m moves to its limits and relates that to the range of voltage the TPS reads. We adjust it so the lower s/m limit is 0.6V so the TPS is adjusted.
  6. rider911

    rider911 Shortcut Navigator

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    If you had some understanding of how the system works you would know that nothing you wrote makes sense.
    The stepper DOES constantly change and is why (when set correctly) that you will get 0.69V cold and 0.60V when warm.
    You set the TPS at idle when the motor is hot, could you post a video of your bike idling while the throttle shaft is resting on the factory setting of the screw
    Where does it say anywhere that the screw you refer to is called an "idle screw adjuster" That is just an assumption you have made without any expertise.



    Looks like you have a good understanding of this system, I'll let you finish explaining it to the people who are looking for guidance.
  7. Mr Head

    Mr Head Adventure Hippie Supporter

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  8. chevtech

    chevtech Long timer

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    I have TONS of expertise with TPS, MAP, SM, ECU systems. Just not on this application. If you don't set a base idle with the idle adjustment screw than you aren't starting with a blank slate. Period. Beyond that I will simply call myself a highly educated student of this particular system, but without a base starting point, it throws so many other variables in there you could chase your dick forever. Which it would seem many do. Miss the base/first step in adjusting a system...yah good luck.


    Edit: I would assume there is a process for setting the idle set (or stop...doesn't matter what you call it) screw. If there isn't we should figure out how to make one that works. With properly balanced throttle bodies it should be achievable to simply set the base idle, (whilst sitting on the idle stop) TPS voltage set to spec while on stop, and then everything else (assuming no faulty components) should just line right up. Adjusting a constantly changing TPS due to Stepper Motor movement trying to hit an ideal that is a moving target as you change ECU inputs (which of course changes ECU outputs, including the SM) by making adjustments sounds a like a recipe for failure, and human introduced error. Does anybody know what the RPM and TPS voltage should be whilst sitting on the idle stop screw?

    This should be the starting point for any adjustments on this system IMO.
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  9. Salzig

    Salzig Long timer

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    +1.
    I work with control system for a living (on two pretty big rolling mills).
    Calibrating sensors is one of the main part of my work.
    You don't calibrate a position sensor that is not locked in a known position. Period.
    Some times you even need two known positions.
    Besides you don't calibrate the feedback sensor when the control system is in closed loop.

    Problem is we have a fixed position (the set screw) but don't know what the voltage should be.
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  10. chevtech

    chevtech Long timer

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    It would seem likely to me that when the stepper motor runs through its' sweep at start-up it is looking for the lowest voltage it sees, corresponding to an RPM that it expects that low point to be, and plugs it into the corresponding algorithm. Could it be that simple, that this is not being accounted for? Does the adjustment procedure not have you set this base point? If so...willing to bet this is a major issue, that could be easily resolved with a known RPM for the base idle, and known corresponding TPS voltage for that RPM/set screw stop.

    Still just a student on this system, but those are pretty inescapable base starting points!


    :beer
  11. DeepSea

    DeepSea electronically challenged

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    Let me start by saying I'm less educated than all of you on here. My background is more based on destroying things rather than keeping anything running. Also English really is my first language. I just don't write (or always speak) like it is so please bare with me while I input my experience.

    What worked for me to properly set the TPS. I'm assuming we are all chasing the erratic idle issues here and not as focused on the Stepper motor function. It's important but secondary IMHO.

    • Replaced the TPS and set to the recommended voltage (Don't remember what that is off the top of my head) with TUNECU. Cold bike because that's what I was stuck with at the time.
    • Bike had been previously tuned trying to troubleshoot why I had the crazy idle. So at this point.
    • Valves already adjusted
    • TB's snyc'd
    • New plugs
    • Throttle cables with enough slack
    • Fuel filter, etc.
    • I warmed up the bike to operating temperature. Read the TPS voltage at PROPER IDLE 1450 rpm (again if my memory is correct). Wrote it down.
    • Shut down the bike. Then immediately retracted the stepper motor and read the voltage. Took note of the difference.
    • With the bike shut off and stepper motor still retracted. Adjusted the TPS by moving it the difference I needed to set the TPS for a warm idling bike.
    • Adjustment done. Fired it up and did the same thing a second time. This time it was a much smaller adjustment.
    All in all I ended up doing it three times to get it spot on (the third time was a couple weeks later). No more issues and I wasn't trying to hit a moving target when I did my adjustments.

    Hopefully my ramblings and weak grasp of the English language paint the picture. If not... well I'm better with pictures, but willing to clarify if asked. :dunno

    Steve

    Note, mine is an 07' w/ Rottweiler kit, Single sided Remus exhaust and running the Hooligan map, with about 35k miles on it.
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  12. mousitsas

    mousitsas Long timer

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    Please dont shoot the stupid in this matter (that would be me).
    Thinking plain and simple, WHY ON EARTH does the s/m need any other feedback to set idle other than the rpm?
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  13. mousitsas

    mousitsas Long timer

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    And as a side note, which might be relevant or maybe not, I remember when we installed a pcv+autotune on deviant666 bike we noticed the following. We set tps up wrong and as the bike started the idle was hunting continuously up and down. However, pretty soon as autotune started doing its electronic voodoo, it became rock steady and at the correct rpm, purely by an adjusted fuel map as it seems.
    So my thinking is that when the idle goes berzerk, there is some sort of "underdampened?" positive loop between the rpm and tps feedback.
    Please forgive the terminology as I dont really know what I am saying.
    So, would it be possible in order to simplify the fault finding process, to replace the tps by an appropriate resistor to provide a steady idle tps voltage?
  14. chevtech

    chevtech Long timer

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    To this point, I would ask the question: How does the ECU know that the bike is at idle?

    Early systems often used an idle switch that was activated when the butterflies were closed, but in this system it knows that through the various sensors, possibly including vacuum level (high when at idle), as transmitted by the MAP, and in this case probably largely (if not exclusively) by looking at the TPS voltage, applying that voltage to an algorithm which in turn tells the ECU that the butterflies are at closed throttle given the voltages it sees, the corresponding low RPM, and lack of TPS change implying that the system is sitting on the SM, without throttle input. It's more complicated than that once it is outside the factory perfect norm, for voltages, and has to "learn" new adaptations as a result, but that is the simple explanation.
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  15. chevtech

    chevtech Long timer

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    I appreciate the methodical nature in which you adjusted your system and hope it is working well, and continues to do so! However! You were most definitely chasing a moving target, which is why you had to adjust it three times! ;) This is less than ideal, but may simply be what we have to work with.

    Did you ever set the base idle screw by some spec that I'm unaware of?

    Just curious.

    :beer

    Todd
  16. Salzig

    Salzig Long timer

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    Sometimes I think the ECU simply doesn't know it.
    On page #1 I posted a plot of a log I made and it shows that the idle SM is moving, chasing my right hand inputs.

    On a side note, when new my bike used to stall randomly. I adjusted the set screw to allow "less closing" (if this makes sense) and cured the issue.
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  17. chevtech

    chevtech Long timer

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    I agree that is likely true the ECU doesn't "know" sometimes that it is at idle, and probably causes many of the problems people experience! I will reiterate if we could just find the right RPM and voltage spec for the idle set screw, we can not only eliminate that variable, but is very likely causing problems for many!

    Just my $.02

    :beer

    Todd
  18. DeepSea

    DeepSea electronically challenged

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    Never moved any screws. Only adjusted the TPS once with a relatively large move then 2 much smaller moves.

    Good luck everyone on fixing the idle issues. Until I fixed it. It was the first and only time I considered selling my bike. :deal
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  19. chevtech

    chevtech Long timer

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    If we could but just find a RPM spec for the idle stop, we could have somebody who had meticulously set their TPS voltages such as yourself reverse engineer a TPS voltage spec for the idle stop by having you set idle stop rpm, and then measure TPS voltages at that point! This would give inmates a starting point to adjust to, that has been verified as having the proper "floating" TPS values and would give them a sound starting point, that may save them lots of grief!

    Interested?

    ;)
  20. DeepSea

    DeepSea electronically challenged

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    I don't mind helping, but am going to need a picture. :lol3

    If I understand you correctly. Your looking for the voltage of my TPS on a retracted stepper motor AND the dimension of the stop screw. Call it top of fastener head to a fixed point yet TBD.