Vector 3 accuracy thread

So here we go... This is the accuracy thread for the V3.

Now for my first post here, I need to inform you, that my comparison is with a Kettler Ergoracer S (2016 model). Note this bike has a flywheel which resistance is being controlled electronic. The bike is calibrated according to a DIN std. and the bikes comes along with the calibration sheet. My bike is slightly below actual wattage. As a simpel test, I do get the same result when doing a FTP test either on Kettler or outside with a different powermeter. So the wattage must be about right.

Back when I had Vector 2, one funny thing, I had to set the pedalarm to 187 mm (actual is 170 mm) to get the same wattage as Kettler(!). Never the less is worked quite well. With that setting I got good comparable data from both sources. So when getting V3 in my hands, I started out setting the pedalarm length to 187 mm. Once done riding, I compared the data. To my surprise and happiness, I found that V3 had to be adjusted to 171 mm to perfectly aligned with Kettler. Sweet thing - so I adjusted to 170 mm. However on the following ride, V3 was clearly not showing enough(?!). Going through the same comparison, I calculated the adjusted pedalarm to now 198 mm...!?!

So my very first conclusion here, based on only two rides indoor on my Kettler with V3 is the following. To get aligned wattage, I see pedalarm length varies from 170 to 198 mm. That's a difference about 16%

Check out the charts below and let me hear your thought...

EDIT: can't upload my second picture. I'm gonna try again later...
ciq.forums.garmin.com/.../1280575.png
  • Former Member
    0 Former Member over 7 years ago
    Teriemer

    The long explanation on handling radio messages is important when it comes to comparing data across power meters and head units. You cannot really compare the data from different power meters accurately unless the head units you are using are handling the data they receive in the same way. If they don't then the head units are introducing some variation in to the data that you are trying to compare.

    So the short answer is that it does not impact the accuracy of the power meter, but it does impact the accuracy of the data you are using to compare the power meters.

    If you want you can bypass the head unit processing all together. If you have an ANT dongle you can use SimulANT from www.thisisant.com and log the ANT messages that are being sent by the power meter and process those yourself.
  • - Cadence in ERG mode impacts the power reported by the Vector 3 pedals, a lot.
    I'm still trying to figure out where I've gone wrong in the mix here.

    gplama: I'm one of the members of the Vector R&D team, and I've been heavily involved in Garmin's development of Vector since the original acquisition of Metrigear. Trying to establish the absolute accuracy of a power meter can be very frustrating because it often requires that you place your trust in some other piece of measurement gear, which may itself have unknown or difficult to control sensitivities.

    In that respect, the Vector team has generally used respected brands of crank spider based power meters to provide comparative data. The crank spider power meters are located 'next' in the power transfer system on the bike, and they do not themselves absorb any power so there is no issue with load-induced heating or variable drivetrain efficiency due to chain position or tire pressure. The power meter also generally has a much more simple task to perform compared to a trainer, since the trainer will be trying to implement some kind of resistance control loop based on internal feedback. In the case of ERG mode, the feedback is complicated further by the introduction of a slow and lossy wireless data link.

    I read your post this morning while I was riding the trainer and so I did a couple of cadence ramps to illustrate the kind of agreement that we would expect to get against another crank based power meter. The attached plot shows the result of going from 45 RPM (1800 to 1890 seconds) up to about 135 RPM (1900 to 1940 seconds)

    We are genuinely interested in understanding why you're getting the results you are getting. We think, though, that when you have the time, it would be great if you could do a hanging-weight test to get an absolute validation of the torque reporting on your Vector 3 pedals.
    ciq.forums.garmin.com/.../1286484.png
  • t_smit Cheers for the reply. What's interesting is that my steady state cadence/power ramp test was also accurate enough for me to be happy. It was the ERG mode data comparison that started seeing the separation when bumping up the cadence. I haven't ruled out the Neo (and Drivo) as the fake news providers just yet..... but I need to get my head around exactly what's going on and who is 'the truth' with the numbers.

    Initial Lama Lab Test with the Vector3 | Neo | (and PowerBeat G2, but omitted.... another story in itself): https://analyze.dcrainmaker.com/#/public/1bcf45e0-9e68-4e5b-45b6-096496c5586f

    Is there a reference somewhere for the static weight test on the Vector3? I have a 10.000kg certified weight... and some interesting bags of water from a PowerBeat calibration kit I can also use :)

  • 20.000kg certified weight + 21g hook/mount. 172.5mm cranks. Calculated Nm: 33.845

    Readings from the Edge 520:

    R: 33.41, 33.50, 33.47. 33.46 avg. 98.86% of calculated Nm.
    L: 33.66, 33.59, 33.72. 33.65 avg. 99.42% of calculated Nm.

    All looks pretty good.



  • Tests 9 and 10.... done... as this is doing my head in.

    Test 9 - Vector 3 | Tacx Neo.

    Post static weight tests on Vector3 (results posted above)
    39/15 gearing. No gear changing.
    Head units: Garmin 520, Garmin 820. 1 second recording. Latest firmware on both.

    - 3 minutes 200W ERG test. Cadence change every minute. (90/60/120)
    - Cycling Dynamics turned off at 5min.
    - 3 minutes 200W ERG tests / cadence change every minute. (90/60/120)
    - Cadence Ramp Test ERG enabled (Cadence increase, power 'should' remain the same)
    - Cadence Ramp Test ERG disabled (Cadence increase, power increase)

    Data: https://analyze.dcrainmaker.com/#/public/25212c06-c1b5-49ea-5ba9-ffdaaa8cd18c


    Test 10 - PowerTap P1 | Tacx Neo

    Everything IDENTICAL to Test 9, except for the pedals. I skipped the 2nd 3minute block I used in Test 9 after disabling Cycling Dynamics (showed no change)

    Data: https://analyze.dcrainmaker.com/#/public/12a100c9-9a80-460e-6050-abf3212b6abe


    The raw data files should be accessible on Ray's site for download / further review. Let me know if not, I'll email them.

    In summary and for clarification - I really really really want the Vector 3 to work, just as well as the P1, it not better. I won't rule out the Neo, my testing protocol, my wonkyness at higher RPM on L/R, maybe the moon phase.... I just can't explain or resolve what I'm seeing with the readings.

    Grabbing at straws...

    - Installation torque? I'm snugging them on just as tight as the P1.
    - Interface between the pedal and the cranks? I've tried with and without the 2mm washers, no change on the Ultegra 6800 cranks.
    - Cleats?.... I'm running 6deg float on V3, 0deg on the P1. I have the 0deg Exustar ones here in a box I'm yet to install.
    - Sample rates.... well beyond what I've got access to see/review/know about. I'll leave that for the engineers.

    I'll box these back up for now so I don't keep throwing more test cases at them....


    ciq.forums.garmin.com/.../1286522.png
  • Hi All

    I just purchased the new garmin V3 2 weeks ago and I've also noticed that power measurement looks changed according to my cadence and the level of power produced when I compare with my smart HT.

    FYI, I have a KickRv1 that I use in ERG mode and I record on a Edge 1000.

    I figured out that GV3 gives values lower than my KickR about 15/20w for low level of power (<200w) and 10/15w of difference when level of power if greater than 400w. This is for cadence under 80rpm.

    However when I spin legs with a cadence upper than 90rpm, measured power is very closed to the ERG power setpoint even a little bit more.

    Otherwise, I have a question about the instant power measured. is it normal to get a big variation of measurement i.e. up to 25/30w when you don't change your cadence and force?

    therefore I display the average power on 3s, the variation is still present but less important.

    Thx in advance for your reply
  • ... I just can't explain or resolve what I'm seeing with the readings.



    Well I'm gonna say it as I see it. There's only one obvious option left; the V3...

    Unless you got a faulty pair? But then they probably also would be off in other cases, in which they're not...

    So maybe there is an issue...? The lab-test I referred to, also indicates tuning needed (although V3 showed too little in that test)...

    Never the less, it's really cool we have Garmin representatives in this thread. I see that as Garmin really want to help us and be involved. I really hope these pedals will deliver and I can't of also believe in they will in time.

    I'm excited to hear Garmins reply...
  • Former Member
    0 Former Member over 7 years ago
    Since I got my V3s a few weeks ago they have been on my trainer bike as I've been keeping an eye on a L/R imbalance I have (which is why I have moved to Vectors from Stages). Anyway, my trainer is a Tacx Neo and is controlled in Erg mode by TrainerRoad for my workouts and I have been recording the V3 figures on an Edge 500. Although I have not specifically been tracking the comparative accuracy of V3 vs Neo as this was not my focus, I have noted that average power readings both for whole workouts and splits within those workouts (for me to see how my L/R balance changes with power and cadence - another story) have typically been within less than 1% of each other. For instance I did a 90min TrainerRoad workout this morning for which TR/Neo recorded a normalised power of 207W and my V3/Edge 500 recorded a normalised power of 206W.
  • Well I'm gonna say it as I see it.


    I'd do that too... but trying to be professional and all. They're boxed up and back on the shelf for now.


  • Former Member
    0 Former Member over 7 years ago
    Seriously considering returning mine