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Thread: TPS Alignment, Idle Speed Adjustment: Beyond Zero=Zero

  1. #1
    Registered User roger 04 rt's Avatar
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    TPS Alignment, Idle Speed Adjustment: Beyond Zero=Zero

    Although I'm not a fan of adjusting the throttle stop screws or TPS, since they're factory calibrated (mine are untouched and are in spec). Many motorcycles have already been altered using the zero=zero procedure (and there may be wear beyond adjustable BBS limits) creating a need to restore either setting. What follows is a work in process based on what was learned in Trail'R's Thread on his R1150GS: GS-911 Error Code Question - Lambda Sensor Related . Comments and questions are welcomed.

    There are three conditions that need to be satisfied at Idle speed for the Motronic, TPS and throttle to be aligned:

    1. The TPS must be registered to the Motronic.
    2. The engine must be warm and functioning in Closed Loop (or on the R1100 European version without catalytic converter, set idle CO to 1.5% using the CO Pot).
    3. The Idle speed must be set to spec (e.g. 1100 RPM, +/- 50).

    I'm not going to provide all the details (e.g. explain how to work the throttle stop-nuts), just the essential steps for #1 and #3 above.

    1. TPS

    The correct method for setting the TPS does not involve a voltmeter since the purpose is to align (register) the TPS to the Motronic; therefore you need an output from the Motronic to know you've got it right. The TPS voltage is an interesting byproduct of the correct procedure.

    R1100
    The diagnostic connector has a TPS calibration pin. You can read about it in a few places:
    A) http://forums.bmwmoa.org/showthread....l=1#post948289
    B) http://www.largiader.com/articles/motronic.html
    C) http://www.k11og.org/forum/viewtopic...er=asc&start=0

    R1150
    A GS-911 is easier to check that the TPS signal is within range but from measurements on my bike if the voltage at idle is 0.35 to 0.38, the Motronic can register it with the following procedure. The exact voltage does not matter.
    A) Remove Fuse 5 (or disconnect battery ground) for 5 minutes, then replace fuse.
    B) Key On
    C) Fully rotate throttle twice
    D) Key Off

    3. Idle Speed
    Refer to this thread for the reason why Idle Speed is important to the Motronic: (starting here, Idle Speed for Correct Mixture).

    The procedure below is so that TPS and idle speed don't interact. You may need a fan for cooling. Also it is important to have clean TBs and cable slack during adjustment. Cable slack re-adjusted per book when finished.

    A) Fully warm up the motorcycle and have a fan for cooling. Throttle bodies and BBS airways must be clean. Loosen left and right cable adjusters for 2 mm slack to insure throttles stay on stops.

    B) Remove the TPS but leave it plugged in to the harness. Set it to the idle position using the Motronic procedure outlined above in #1 (Diag Connector for R1100; TPS learn before removal, then GS-911 set to 0.32 degrees for R1150). (You could measure with DVM to learn thevoltage before removal and make sure it stayed set there.) By doing this, no matter what you do with the throttle stops, the Motronic will see IDLE input from the TPS and interaction is eliminated.

    C) Set the BBSs to 2.0 turns, whatever is considered the neutral position.

    D) Perform a TB sync & Idle Speed adjustment using the throttle stops and get as close as you can to idle spec. Then use BBS for final fine tuning. It is imperative that the idle speed is exactly the book value (1100 +/- 50 rpm for the R1150). Because the TPS is removed, it did not vary while you adjusted idle.

    E) Attach the TPS to the left TB and set per procedure outlined in point 2 above.

    When completed you will have the TPS registered, BBS at about 1.5 turns and the motor idling at spec (1100 RPM on an R1150).
    RB

  2. #2
    Registered User roger 04 rt's Avatar
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    Critique of Zero=Zero

    As I mentioned at the start of the thread, I'm not a fan of adjusting the TB Idle Stop screws but if you're considering zero=zero, or if someone has previously run zero=zero on your Oilhead, there are some issues with that procedure worth knowing. First, as I described at the start of this thread, the TPS may not be correctly registered to the Motronic because setting the TPS to a particular voltage does not have a specific meaning to the Motronic (it has a signal to tell you when the TPS is set correctly). Second, the throttle is left opened too far by the zero=zero procedure.

    Here are some facts about the TPS sensor from the Bosch data sheet.
    1) It has two precision potentiometers inside. One is for smaller throttle angles, the other used from mid-range through WOT. It is the same part on R1100 and R1150. Data sheet here: Throttle Position Sensor (Bosch 0 280 122 201).

    2) The finer range goes from zero to 23 degrees and varies by 187.5 mV per degree of rotation. That means each 20 mV is only 0.1 degrees. (An adjustment from 360 mV and 380 mV is almost too small for the Motronic to measure, and certainly has no effect.)

    3) The finer range has a divider ratio of 0.05:1 at zero degrees, which is about 250 mV.

    Point 3) has serious implications for the Lentini zero=zero procedure. It directs you to set the TPS to 10 mV at fully closed throttle. Based on the TPS spec, it should be set to 250 mV. Next zero=zero directs you to adjust the throttle stop screw until the TPS is 370 mV to 400mV. That means the throttle is opened 1.9 to 2.1 degrees as you adjust the throttle stop.

    If we assume that the Motronic is looking for approximately 350 mV (based on the GS-911 TPS checker) or 385 mV (based on zero=zero), or 360 mV by my calculation, and that the TPS spec is 250 mV for zero degrees rotation, then the Motronic is expecting that the throttle is only open 0.5 degrees to 0.7 degrees when the throttle is on the stop. (350-400 mV minus 250 mV at zero, divided by 187.5 mV per degree of rotation.) On the R1150, the GS-911 reads 0.32 degrees from the Motronic after TPS cal, that would suggest that my estimate of 0.5-0.7 degrees is too high but compared to the 2 degrees of throttle opening produced by the zero=zero procedure, it is at least closer.

    The only conclusion you can reach is that zero=zero opens the throttle about 1.5 degrees too far when on the stop, and that it is always open 1.5 degrees more than the Motronic measures. The consequences of this: the Motronic will output less fuel in the first few degrees, meaning it runs lean, a condition fixed later by mixture adaptation (consuming some of the adaptation range needlessly). Also, since the throttle has been opened too far by zero=zero, the BBS screws have to be closed down to compensate, which I believe is why some find that after using the zero=zero procedure, they cannot reduce their idle sufficiently.

    As I said at the outset of this thread, it is a work in process. I hope there is someone with an R1100 who will be able to make some measurements, feel free to PM me if you'd like to help.
    RB

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    MOA #24991 Pauls1150's Avatar
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    This is some great info - Thanks for being so persistent, and so thorough, with this research!

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    Quote Originally Posted by Pauls1150 View Post
    This is some great info - Thanks for being so persistent, and so thorough, with this research!
    +1 from me.
    We may need a "Throttle Body Tuning for Dummies" as prerequisite reading, for the basics.
    --
    Doug Raymond
    R1150RT '02
    Ambler, PA

  5. #5
    Registered User roger 04 rt's Avatar
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    Thanks guys. As I mentioned, this is a work in progress and I expect some tweaks to the procedure.

    I think the most important point is that when the throttle is fully closed, the TPS should read 250 mV. So the idea of the process would be zero=250mV (as opposed to zero=zero). And at idle, the Motronic is expecting the throttle blades to be open somewhere between 0.3 (what the Motronic reports) and 0.6 (what I calculate).

  6. #6
    Registered User Blacque Jacque Shellacque's Avatar
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    This is great work and thoughtful analysis. Thanks.

  7. #7
    Registered User roger 04 rt's Avatar
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    Comment on Earlier Posts
    In the earlier posts in this thread there are mistakes or omissions that I have found. The biggest error is the conventional understanding of what rotating the throttle does after a Motronic reset and recal. As I mentioned, this is a work-in-progress. I have a new recommendation for zero=250 later in the post.

    New Measurements
    I spent a few hours yesterday making measurement of the TPS and Motronic for small throttle angles and found quite a few interesting things. Among the things I learned (and although I can see vestiges of the factory paint), I see that someone performed zero=zero on my R1150 since there is no fully intact paint. The BBSs are about equal so I'm not too concerned but will go back and reset it at some point.

    To make the measurements, I attached a good DVM between pins 1 and 4 or the TPS and connected the GS-911 to the diagnostic port. This way I could measure the voltage change versus throttle angle change as reported by the Motronic. I was careful to move the TPS very slowly (by rotating it with the throttle lock on), and find the trip point for each reading of the GS-911. It outputs angles with a resolution of 0.32 degrees. So the angles it registers are: 0, 0.32, 0.64, 0.96, 1.28, 1.92, etc. I also monitored the Idle Switch Off indicator reported by the GS-911. Lastly, I measured (and then calculated to confirm) how much physical rotation of the TPS per 10 mV (it's tiny) of voltage change on pin 1 (the high resolution wiper).

    Here's what I've found:

    1) TPS cal (rotating the throttle) does not have any effect on the voltage-to-throttle angle as measured by the Motronic. This was a surprise because we all "believed" that TPS cal (rotate the throttle twice) learns the idle and full scale positions. I set the TPS as low as 300 mV and as high as 375 mV, performed a full reset (10 minutes) and recal. In spite of that, the point at which the Motronic/GS-911 transitioned from reporting 0.32 degrees to 0.64, 0.96 and the point at which the Idle Switch reported OFF were the same whether I set the TPS to 300, 350 or 375 mV.

    It now seems clear to me that the reason for setting the TPS is to position it to 0.48 degrees, which is always approximately 340 mV to 350 mV.

    2) The A/D converter in the Motronic is 8 bits (expected) and the step size for each "bit" of the A/D is approximately 20 mV. The Motronic reported step sizes are 0.32 degrees, which equals 60 mV, which means each bit of the A/D is about 0.11 degrees (20 mV). That means one degree is about 200 mV (187.5 to be exact). So the angle to voltage conversion measured (and then calculated by me) below. Because the A/D has some tiny fluctuations (noise) these values can change by 10-20 mV.

    0.00 degrees: 250 mV to 309 mV
    0.32 degrees: 310 mV to 369 mV
    0.64 degrees: 370 mV to 429 mV
    0.96 degrees: 430 mV to 490 mV

    Idle Switch Off: ~430 mV

    3) Using a feeler gauge under the throttle stop, I measured that every 0.1 degree of TPS rotation is about 0.0025" of movement at the TPS locking screw. This means a 10 mV change in DVM reading is the result of about 1-2 thousandths of an inch of movement!

    4) On my R1150 the A/D "noise" at small throttle angles seems very good, less than one bit. That means that sometimes the transition for, say, 0.96 degrees is at 410 mV and sometimes it is at 430 mV. 0.96 degrees is the point that the Motronic reports Idle Switch: OFF.

    5) If you want to readjust the TPS and throttle stops (because someone else changed them) zero=zero is the wrong procedure. It certainly leads to the throttle angle being opened too much (10 mV at zero degrees, then to 370 mV, which means the throttle is opened 1.92 degrees). Based on a 340 mV target for the TPS (confirmed with the GS-911 and equal to the mid-point of 0.32 degrees), the throttle is meant to be opened about 0.48 degrees and the rest of the air comes from the BBS. (I could be off a bit on the 1.92 degrees since there is no spec for angular rotation below 250 mV on the Bosch TPS.)

    Looking at the TPS data sheet, I have an explanation for why the requirement to rotate the throttle twice after a Motronic reset on the R1150 (the R1100 may be learning it on-the-fly, or BMW may have fixed a problem by introducing the procedure on the R1150), since it doesn't seem to calibrate the end point. There are two potentiometers in the TPS. The fine-tps (0-23 degrees throttle) has it's upper and lower points specified. TPS-coarse has only it's upper point spec'ed. That means that rotating the throttle allows the Motronic to measure and learn the crossover point and the start of tps-coarse. It may be doing this by using the fine-tps to measure the starting point of the coarse-tps, thereby having a seamless crossover between the two.

    Also, I now also can see why moving the TPS idle setting to 370-385 mV can affect engine operation, at least temporarily, especially on the no-cat configuration of the R1100. At that voltage, the Motronic is just starting to register 0.64 degrees, so the Motronic then goes up to the next 0.32 degrees more quickly. This would give a slight rich fueling bias for throttle angles below (I'm estimating) 5 degrees. I doubt that it is a permanent benefit but could be, very slightly around idle. (Going a little further with the reasoning, since zero=zero opens the throttle too much, it makes sense that a higher TPS voltage would get the TPS reading by the Motronic closer to the actual throttle-angle-plus-BBS air flow. On the Closed Loop Oilheads, Adaptation Values will fix this up, but as you know, adaptation is not perfect. Therefore, it is better to get it right from the start.)

    Recommendation
    The procedure I suggested earlier in the thread for restoring the throttle stops and TPS will work but now seems too complicated. I also realized you can set the TPS with voltage, something I didn't think was possible because of the conventional-wisdom of what rotating the throttle twice did after reset. I still believe that the GS-911 or LED (for R1100) is the preferred route for setting just the TPS because it is a Closed Loop process that includes the Motronic.

    Although I don't advocate changing the throttle stops or TPS, for someone (like me?) who has had their TPS Lentini-ized by zero=zero and wants to get it set correctly, a zero=250 procedure can be used.

    Begin by setting zero degrees throttle to 250 mV (instead of 10 mV recommended in zero=zero). Then the left throttle should be rotated to 340-350 mV, which will rotate the throttle open 0.48 degrees. Then just follow the rest of the Lentini procedure. That will undoubtedly require the BBSs to be opened more than two turns. I will experiment with this on my bike to see how many turns are required when I have time.

    Next Tests
    My next experiments will be to close the BBSs and see how much the throttle needs to be opened to idle at 1100 and at an AFR of 14.7 to 1. Then I will see how many turns the BBSs can be opened before the RPMs stop increasing.

  8. #8
    Registered User roger 04 rt's Avatar
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    With the recent measurements above, I've concluded that the MA 2.2 and MA 2.4 behave the same. Each has a nominal setting of 340-350 mV for center of the 0.32 degree range, meaning that the expected factory throttle angle is about 0.48 degrees. Here are some measurements taken on an Australian R1100RT:

    "The TPS Cal LED is ON only between .327mV and .386mV as measured with my Fluke meter on my TPS."

    This is essentially the same range that I measured on an R1150 the other day. And the same range reported by the GS-911.

    That means that the LED confirms that you are within the proper range. Note that it is almost exactly 60 mV wide, the width of 0.32 degrees, which is the Motronic minimum angular step size reported to the GS-911.

    I can't think of a test to confirm that the function of TPS alignment on the R1150 is to align the two potentiometers inside the TPS module, but it is my best explanation, given that: a) TPS alignment doesn't affect the bottom of the range, and b) that the exact angle at WOT is not critical.

    The R1100 (without the procedure to twist the throttle twice either: a) has no such alignment or b) does it automatically as and when the throttle moves through the crossover point. I don't think we'll ever know.

    Zero=zero opens the throttle vane 1.92 degrees when the lefthand stop screw is adjusted from 10 mV to 250 mV, however, the Motronic only reads 0.32 or 0.64 degrees. Then if you open the throttle another 1.28 degrees, the throttle vane is actually open 2.20 degrees but the Motronic reads 1.6 degrees. In other words your Motronic is always reading incorrectly lean.

    Zero=250, as described above results in the actual throttle angle being the same as the measured angle as read by the Motronic, neither lean nor rich.

  9. #9
    IBA #44567 Ken F's Avatar
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    Great info Roger, and thanks for taking the time to document all of this and especially to share!

    Makes me understand why my R1100RSL has so many lean pops coming out of the tailpipe!

    Ken
    IBA #44567 Pres. Springfield BMW Roadriders
    "Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
    -Albert Eienstein

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    Registered User roger 04 rt's Avatar
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    Here is a post from another forum, detailing a re-alignment of TPS and throttles on a 2002 R1150GS that is long but interesting.

    Quote Originally Posted by Jim H View Post
    Warning: this is a very long post!

    Reader’s Digest version – my R1150GS throttle body idle position stop screws and TPS mounting screws had little or no blue anti-tamper paint on them when this bike was acquired. Several recommended methods for resetting these stop screws and TPS to their OEM positions were reviewed and many trial and error settings were tested. Best results of all were achieved using the Zero = 250mV method as described in post #7 of this thread.

    Beginning point: new (to me) 2002 R1150GS, 57K miles at acquisition time, all stock except no canister, with 4 prior owners. Acquired and rode it 3300mi to WA State Sep ’14 and made this 5-day trip without issues, avg mpg 38. General running condition: OK enough to make this trip, but not great… It felt like the engine needed a good tune as a minimum.

    A winter project was undertaken to restore this bike to a proper and reliable running condition. The work that affected state of tune included valve clearance adj; rocker end play adj; replaced air filter, fuel filter, and all in-tank hoses and clamps; cleaned the fuel tank internals, air box, intake tubes, and engine intake ports interiors; fuel injectors sent off for professional cleaning and flow test; disconnected and lubed all electrical connections; and the engine compression, fuel system pressure and fuel flow were verified to be within spec.

    During prior attempts to balance TB vacuum at idle using a TwinMax the BBS adj seemed vague and would not steady up at a balanced position. Also, because both TB shafts were rattling, the TBs were removed for thorough cleaning and to install Dan Cata TB rebuild kits. Found a lot of thick built up crud in the BBS ports that was likely part of vacuum balance problem. Original BBS setting position was almost closed. Also found and removed a small rock imbedded in the groove of the LH TB cable pulley that essentially shortened the LH throttle cable. No blue paint was evident on the LH TB pulley stop screw/lock nut and only a remnant on the RH TB stop screw and bracket. With no continuously intact OEM anti-tamper paint on the stop screws, the likelihood was that a previous owner or independent shop had adjusted them from OEM idle position. The BMW repair manual does not address adjustment of the throttle body idle stop screw setting and for the TPS setting refers to the use of the “BMW MoDiTeC” for setting after installation. The parts fiche for this bike shows the throttle body already populated with the butterfly, shaft, return spring, stop screw, etc as a single OEM part number and the nearest BMW shop advised that they replace TBs that have had the OEM stop screw positions altered before they’ll work on anything related to the TBs. Not wanting to go that route, forums were queried for information.

    After much reading on this topic in the various BMW MC-related forums, several relevant threads, including this “beyond zero=zero” thread started by Roger were found. Having then read all the threads and articles I could find pertaining to setting the TPS and stop screws correctly for idle position, it was evident that virtually all recommended methods involve the following steps:
    1)fully close LH TB butterfly verifying no contact at stop screw.
    2)using a good digital volt meter (DVM) attach its positive (red) lead to a jumper wire connected to TPS electrical connector terminal 1 and attach its negative (black) lead to one of several varying recommendations for ground connection. Some say TPS terminal 3, some say TPS terminal 4, some say LH TB ground wire, some say engine ground, etc.
    3)rotate TPS until an indicated TPS voltage of a particular value corresponding with the butterfly in the fully closed position (zero position) is read on the DVM and tighten the 2 TPS mounting screws. This is the second area of varying recommendations but the smallest recommended TPS voltage for fully closed butterfly position (zero position) is 10mV and the highest is 250mV.
    4)while counting screw turns, rotate the LH TB cable pulley stop screw until a certain TPS indicated voltage for the butterfly in the idle position is read on the DVM and then tighten the locknut. This is another area of varying recommendations but the smallest recommended open position is 100mV higher than the zero position voltage and the highest recommended open position is 400mV higher than the zero position voltage.
    5)Using the same number of screw turns as in step 4, set the RH TB pulley stop screw the same number of turns.
    6)Reassemble everything, verify all cables have slack and cable sleeve tips are in their adjuster sockets.
    7)Start engine, warm to 4 bars and complete vacuum balance at idle and at 2500 rpm.

    When disassembling the throttle bodies I began with the RH TB and found a remnant of blue paint on the stop screw, lock nut and bracket that suggested it may in fact be where the screw had originally been positioned by OEM. The paint was cracked and broken in places but, again, it looked like it aligned so this position seemed like a good baseline for where the stop screws should be set. By counting the 2+5/6 ccw rotations until no contact with the stop and by measuring the clearance from butterfly to bore at top of TB bore (0.003-in), there were 2 repeatable references for restoring these settings. Further, the amount of butterfly movement from fully closed position to this 2+5/6 turns of the stop screw idle position was measured at the top center of the butterfly by dial vernier. From the top center of the intake end of the throttle body to the top center of the butterfly, from fully closed to idle position the butterfly movement measured .041-in. Using an online angle calculator the open angle at idle position was ~2.65 deg from zero position (fully closed). Interestingly, when I later disassembled the LH TB, which had no blue paint evident anywhere, the stop screw turns, and butterfly clearance to bore were the same as the RH TB so this was more evidence that this was where the stop screws were supposed to be for idle position.

    After thorough cleaning of the throttle bodies Dan Cata TB rebuild kits were installed without difficulty. Very complete kits by the way. For those considering rebuilding their bike’s TBs, these kits are recommend. Because it wasn’t clear whether or not the idle stop screws and TPS had or had not been tampered with, after the TBs were fully assembled, experimentation began with different butterfly idle positions using the LH TB, beginning with the stop screws and the TPS in the same setting position as when disassembled, with the TPS connected to the bike’s connector. Specifically, butterfly movement compared to TPS voltage output within the above mentioned range of recommended idle positions beyond the fully closed position was looked at using the various recommended TPS voltage settings for the fully closed position. It was found that with the TPS mounted where it had originally been positioned, with the butterfly fully closed (stop screw backed out and not in contact with the pulley stop) the TPS voltage was 6mV (as low a reading as it would go without forcing it). After adjusting the butterfly to the original idle position with the stop screw, it was evident that the butterflies on this bike had been far more open at idle position than even the 400mV highest in the range of recommendations! Now what?

    Knowing that this bike ran well enough to make short work of a 3300 mile trip across country without issues, I was convinced the correct setting of the stop screw for idle position had to be further open than any of the recommended setting methods indicated. So, I decided to start where the TPS and butterfly idle positions had been when first disassembled, and where the BBS had been set, which was less than 1/2 turn. After assembly it started and an idle vacuum balance was attempted, noting that the BBS adjustment now had some affect but seemed to have little effect in terms of magnitude of change. It would take a good half-turn to show TwinMax needle deflections. Also, the engine was idling at much higher rpm than before (about 1600rpm) and the BBS had little effect because of the amount of air coming around the butterflies. To reduce the idle speed I knew the butterflies would have to be closed more at idle position but didn’t know by how much.

    It was fairly clear by then that the OEM TB adjustments had been altered, possibly to compensate for poor injector performance and restricted air intake. The pre-cleaning flow test and spray patterns on the injectors were indicative of clogging in the injector upstream filters and the injector flow rates and spray patterns were outside of 15% of equal for the two. The post-cleaning results were well within spec and within .05% of equal. Also the installed air filter when acquired was a K&N that had been too heavily oiled. The combination may have led a prior owner or independent shop to attempt adjusting the TBs to overcome the operating conditions caused by these component problems. As mentioned earlier, part of the winter project work included professional injector cleaning and replacement of air filter with a Mann dry paper element filter and now the idle rpm was ~50% too high at the old settings.

    Further trial adjustments were made with gradually increasing TPS voltage at fully closed butterfly and gradually reduced butterfly idle angle using the stop screw but whenever the butterfly idle position was higher than 400mV above zero position, idle was still too high and BBS had little effect on lowering idle rpm until they were nearly closed. More trial adjustments were made varying the TPS voltage output with the butterfly in gradually less open positions from closed position.Eventually, with the idle stop screws turned 1-1/2 turns, the TPS voltage was adjusted to an indicated 350mV and the engine started and appeared to be running much better and the idle speed could be controlled by BBS adjustment. I thought I had it at least close to right. I borrowed a GS-911 and ran a cold start real time data log and sent it to Roger for his review and comment, fully expecting he’d agree that I had it right… Wrong!

    There were several line items of data in the cold start log that I didn’t at the time either fully understand or appreciate the significance of that indicated problems. After Roger’s gently stated, “not even close” reply I considered options and decided to use his recommended butterfly idle position of 100mV open beyond 250mV set at fully closed butterfly, which was both the maximum recommended value of TPS voltage setting for fully closed position and the minimum recommended value of TPS voltage change from fully closed to the idle position. I dreaded the thought that a lot of time would likely have to be spent to zero in on the correct values with several iterations of changing these settings to somewhere between where Roger’s method would have these settings and I where I had thought it was close to right. Wrong!

    The TPS and stop screws were set as Roger had recommended. His method has you connect DVM red lead to TPS terminal 1 and black lead to TPS terminal 4 using jumper wires. Turn on ignition and ensure the LH TB butterfly is fully closed before rotating the TPS to an indicated 250mV reading, and then tighten the TPS mounting screws to lock in place. Then, while counting turns, adj the stop screw to an indicated 350mV and tighten its locknut. Then turn RH TB stop screw the same number of turns and lock in place, followed by setting both BBS to 2 turns open before starting engine.

    When resetting the LH TB, the stop screw “turn count” to attain a TPS voltage of 100mV beyond the fully closed position voltage of 250mV was just over 1/2 turn (~45deg past 1/2 turn to be exact or 225 deg cw rotation from first contact with the stop). Wanting another way to confirm that the RH TB was set equally, a dial vernier was used to measure the distance the butterfly moved from fully closed to idle position, as done during initial disassembly to determine where to put them back to the old settings. Total movement now was only 0.0060-inch, which equates to an open butterfly angle at idle of only 0.388deg or ~15% of the old angle at idle! With a bright light shining in one end of the TB just a very thin ring of light could be seen all around the butterfly. The RH TB was then set to the same small “thread count” and the same 0.0060-inch difference was measured between fully closed and idle positions. At the time I thought this barely open throttle position at idle was not going to be enough to even allow the engine to start. Wrong!

    After reassembly all cable slack was verified (this is very important to do), the start button was pressed and it started! It was idling at only 800-850 rpm with no throttle assist but very smoothly. The former fairly significant engine vibration at idle was completely gone. My fast idle lever had taken a dump somewhere during the prior runs and I didn’t want to take the time at that point to look into it. An aftermarket hand throttle stop “cruise control” was therefore engaged to hold rpm at ~1500 for warm up, adjusting the throttle downward once or twice as the idle speed increased during warm up to 4 bars. The GS-911 data logging failed to record on this first run with new TPS/stop screw set points but the idle vacuum balance with BBS (which were now quite sensitive to adjustment), and for higher rpm with RH TB throttle cable adj (which also was now sensitive to adjustment) was done using TwinMax. Then, some balancing of vacuum during throttle transitions was done using both BBS and RH TB cable adj, followed by both idle and 2500 rpm balance being tweaked back to center with minor adj. During this vacuum tuning process the GS-911 real time data was running and I noticed the indicated throttle angle was flipping from .32 to .64 degrees. TPS mounting screws were loosened a bit and light taps on the TPS mounting flange nudged the voltage reading from 350mV to 340mV at idle. The GS-911-indicated throttle angle was then holding steady at .32 degrees. The idle rpm was still a bit low after warm up so both BBS were turned small and equal amounts open to increase idle until 1100 +/- 50 rpm was steady with vacuum balanced. The engine was idling very smoothly and there were no exhaust burbles or popping during throttle down transitions. Right on!

    After a cool down period assisted by fans the engine was started again and a cold start data log was taken, the data file was sent to Roger and I went for a ride. The before and after change in engine feel and performance was pronounced. Throttle response was now very “lively” on both acceleration and deceleration. The “seat of pants” feel was more power available and more quickly in a broader range of rpm. Specifically noteworthy was the pull that was now available at lower rpm in the higher gears. On hard acceleration the front suspension now extended near fully and getting up to speed quickly on freeway onramps was no longer a challenge. Also noted was dramatically reduced vibration throughout the rpm range. Right on!

    The only “negative” was the hunting or surging felt in 3rd gear doing ~35mph at ~3000rpm. This surging had been there before but now it was more pronounced. I’ve since acquired an AF XiED to hopefully diminish this surging and will install it sometime soon.

    After Roger’s positive review of the cold start data log, success was declared, the tank was topped off and I took a long ride, some county roads, some changing elevations, some freeway, etc. The Motronic had been reset and I was being attentive to getting as much steady throttle time in varying rpm ranges and varying gears to support the adaptive learning process of this ECU. The delayed drop in fuel level bars suggested increased mileage and the low fuel warning light didn’t come on until 235mi on the odometer. Previously, the warning light was coming on no later than 190mi. The calculated mileage on this first full tank was 8mpg better than prior average. It will be interesting to see if this holds up. The only place imaginable the excess fuel could have been going prior to this readjustment of the idle position and TPS is out the pipe. The spark plugs hadn’t shown fat running indication but I had noticed a fairly dense black soot coating at the muffler’s exit port before I cleaned it.

    So, my conclusion after this trial and error process of setting the throttle stop screws and the TPS position is that Roger’s zero=250mV method works and works well. Had I ignored that this bike ran well enough to cross the country without problems and ignored its TPS and stop screw settings as they were when it did that, this would be a much shorter post! Had I followed this zero=250mV method for the first trial set up, that would have taken maybe an hour or so and the tuning process after initial setup would have taken maybe 30 minutes. I follow Roger’s deduction that zero=250mV of TPS rotation with butterfly fully closed (zero position), and agree. I also follow his calculation process that led him to recommend a stop screw setting for butterfly position at idle of 100mV of TPS indication beyond the 250mV setting at zero position (TPS voltage at idle should be 350mV), and agree. However in this case, as mentioned above, 90mV over zero position (TPS voltage at idle was changed to read 340mV by slightly rotating TPS and tightening mounting screws) kept the GS-911-indicated throttle angle steady on 0.32deg. Note that resetting the TB stop screws to a TPS indicated 340mV at idle position is likely the more correct way to move off the flip point between .32 and .64deg. I just took a “short cut” and moved the TPS a tiny bit to read 340mV. Regardless this probable transgression (sorry Roger), my ’02 R1150GS engine is running smoother and performing better than it may every have been, and that’s enough validation of this zero=250 method for me.

    I’ll add here that my nearly 40 yrs of experience, mostly successful, in tuning multi cylinder, multi carburetor motorcycle and auto engines was of little use toward trying to figure out how to tune an engine where you have no adjustable control of fuel flow and no tech manual prescribing the settings for the TPS and the throttle stop screws. Setting the TPS to the correct voltage output to correspond with the correctly set mechanical butterfly angles at both fully closed and idle positions is critical for this engines ECU to determine the timing and duration of the appropriate fuel delivery signal to the injectors. There’s little doubt that the TB stop screws and TPS positions are factory set by Bing (OEM) to a precision degree by bench test methods, likely using calibrated air flow measuring devices and other precision instruments. It is also likely that trying to replicate this level of precision by users in the field will not be as accurate. However, the Motronic ECU appears to be capable of dealing with such inaccuracies, as long as they are within a tolerable error band. After all, this bike ran adequately across country at cruising speeds of up to 85mph with TB adjustments way out of whack and with partially fouled injectors and air filter. Truly marvelous engine to have done that!

    ...

  11. #11
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    04 1150rt tps

    Thanks for this post... Great info... To cut a long story short... I found the LH TB stop screw in the lower fairing! On cleaning and inspection, the paint on the TPS screws was broken up but looked to be in the right place... However, the pin 1 & 4 measured 3mv. I set the BBS TO -2 turns and the stops to 100mv and started the bike... Idle was very smooth but at about 850RPM cold. From this and the above post, I conclude that the TPS has been re-set, and plan to try it at zero= 250mv... However, I notice that the voltages are all negative with the DVM red on pin1? otherwise it all seems to respond OK. Any ideas?

  12. #12
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by ninja View Post
    Thanks for this post... Great info... To cut a long story short... I found the LH TB stop screw in the lower fairing! On cleaning and inspection, the paint on the TPS screws was broken up but looked to be in the right place... However, the pin 1 & 4 measured 3mv. I set the BBS TO -2 turns and the stops to 100mv and started the bike... Idle was very smooth but at about 850RPM cold. From this and the above post, I conclude that the TPS has been re-set, and plan to try it at zero= 250mv... However, I notice that the voltages are all negative with the DVM red on pin1? otherwise it all seems to respond OK. Any ideas?
    It's easy to mix up pins 1 & 4. Double check that first. If they are good, put your black DVM lead to battery negative and measure pins 1, 2, & 4. Pin 4 should read 0 - a few mV, pin 2 should read about +5 V, and pin 1 should read 0 - +500 mV depending on how you have set the TPS. Be very careful to not short one pin to another, and be very careful to set you DVM to DC Volts. If you short any pins you can damage the Motronic.

  13. #13
    God? What god? roborider's Avatar
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    Roger, I always enjoy your technical posts. I print these (and many others) and keep them in my service binder. Very nice. You put a lot of work into this and you need to know it does not get wasted and ignored.
    Rob C. , Raleigh, NC
    '10 R12RT, R90/6
    2007 CBR600RR & 09 V-Star
    Suzuki DR 350

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    04 1150rt tps

    Thanks Roger... I screwed up by assuming that the pins were read left to right but found them marked on the TPS socket! The main problem I'm having now is keeping a consistent reading... also when I set Zero to 250mv the paint marks seem way off but at the originally measured 003mv, they seem pretty much spot on... not sure what's going on but I'll play around with it this week... thanks again for a fascinating post...

  15. #15
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by ninja View Post
    Thanks Roger... I screwed up by assuming that the pins were read left to right but found them marked on the TPS socket! The main problem I'm having now is keeping a consistent reading... also when I set Zero to 250mv the paint marks seem way off but at the originally measured 003mv, they seem pretty much spot on... not sure what's going on but I'll play around with it this week... thanks again for a fascinating post...
    I have blue paint on my TPS and throttle stops, and no need to adjust. Next time I have the bike apart though I will back off the Left throttle stop and measure how far open it is, using the TPS. The reason your adjustment is so touchy is because every 10 mV is about 0.05 degrees of throttle plate movement, which is tiny.

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