So you must be saying that the issue is bumping your watts across the board, and not just like shown in your power graph comparison, only giving you free 25 or so watts when you stop pedaling?
correct - please see if you can view my screenshots above, I realize they arenât that easy to see. Please note the difference in average watts for that effort - it is huge. In one of my posts above, I attempt to categorize this âphantom wattâ issue as an overall bump, on the order of 10-15%. In that short 4-minute sample above, you can see what happens. My average w/kg is 2.3 vs. 2.6, and average watts is significantly different.
Apologies - trying to make sure I clarify. In the screenshots, I move my cursor to the point where I was coasting, to better visualize the cadence difference and watts - however, on the top portion of the chart, you can see the effect across all data points on the ride itself. I havenât tried to match discrete data points in this ride, as it is difficult to do, but there is more going on than these phantom watts simply happening when not pedaling - I am positive. I believe that watts while pedaling are being boosted by between 25-39 watts (this is the range I believe I see when Iâm not pedaling at all) - and the math seems to check out, from the perspective of my actual performance and abilities. Said another way, if I subtract 25-39 watts from all my recent power PRs (from 1 - 120 minutes), it would be very close to what I think Iâm capable of. I will point out, that the effect doesnât have nearly as dramatic effect on the neuromuscular zone, but that too is bumped.
I donât know if its across the board, but I do suspect that if calibration has been upset, then any time the flywheel is spinning at high rpms, there may be additional watts added.
The reason I suspect this is because when the issue is present, coasting at low flywheel speed does not cause a non-zero reading. Its only after a push and getting the flywheel spinning that watts go to 0 and then jump up to 5 to 20 watts. It doesnât matter what power you produce, its
about the flywheel speed, so you could get it spinning up at very low resistance.
Unfortunately there is no way to know for sure if this is happening when pedalling, but assuming the same behaviour, I believe there may be a flywheel rpm âwindowâ where these ghost watts are being added.
From my testing, if you can coast at high flywheel speed with 0 watts, then there seems to be no calibration discrepancy against dual recordings. - which is most of the time.
But, if you do see coasting watt spikes (and there are YT videos of races where you see this happen ) then I think they are probably getting a watt benefit throughout the race but only at high flywheel rpms.
I was convinced it was a belt tension issue that was being caused by the additional mechanical stresses from virtual shifting, Iâve also considered that its an algorithm issue if using the larger chainring.
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Most of the users wonât even know about the problem. Theyâll just be raving about virtual shifting on Facebook and thinking they got faster or slower based on whether they did a firmware update. 
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Will it be possible for Zwift to check for firmware leveles in the affected devices and DQ anyone who hasnât applied the fix?
From Zwiftâs side, perhaps they could figure out a way to disable virtual shifting for any kickr that does not have latest firmware update once itâs released?
unlikely. But as Paul suggests, for those that do update their firmware, Zwift Racing Score might have come at the right time.
Having said that, we need to give people the benefit of good intentions. I think most people are oblivious to the issue, and those that arenât have spoken up in the community (and had units replaced under warranty) and are diligent about calibration and whether they can coast. Some even resorting to turning off virtual shifting.
If we take this in proportion, we have racers on spin bikes and wheel on trainers who are wildly uncalibrated.
Most racers are trying to do the right thing.
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Possible for sure but I would put the odds of that happening at exactly zero or a bit less. And itâs certainly not the fault of those riders who bought the product claims.
It would help a lot if @GPLama or DC Rainmaker investigated the problem and posted some numbers about it.
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To validate extra watts WHILE pedaling. I realize there is a small time offset, due to trying to push my Garmin at the same time as ending the zwift ride - but I donât believe this would change the results too much. I attempted to place my cursor at 3 minutes and 30 seconds into the ride, it is very obvious which one is which - and here we have a 33 watt difference, while pedaling, between the two screenshots. As a reminder, the one on the left is from my Favero Assiomo Duals and Garmin 840, the one on the right is my Kickr v6 with Cog v2, using virtual shifting.
I attempted to leave a message on GPLamaâs video on the Cog v2 (at least I think it was that one), but I havenât checked on whether he replied.
I agree, give folks the benefit of the doubt, but at the same time I doubt folks are frequently or periodically searching for trainer firmware updates if nothing is obviously broken.
it depends what and how they race.
I first noticed it when I was desperately trying to super tuck for recovery down the Epic. I race in camera 3 so it wasnât immediately obvious until I realised I was losing speed and riders were over taking me.
I then had to pedal downhill - which I hate - and assumed it was the belt tension because I had spent 20 mins climbing out of the saddle on the way up the Epic 
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Unfortunately, it might be worse. Here is a screenshot at the 30 second timestamp. I do not know the extent to which data polling and time offsets might play into this - I believe it could possibly result in a relatively decent variance, but this is pretty bad. This is a 60 watt difference here:
Regardless of anything else, I believe it is evident that the phantom watts are present whether pedaling or not (in the sample ride provided). It resulted in a significant discrepancy in average watts, w/kg/, distance travelled, speed, and energy expenditure. This is not exactly great news for someone who really enjoys the data aspect of cycling - going to take me some time to purge GoldenCheetah, not sure whether I want to mess with Intervals.icu or what.
not quite sure how to read that, but looks like 277 vs 217. I wouldnât read too much into that and would look more at average power over a longer time frame. Are you using dual sided power meter as a pedalling imbalance will add to inaccuracies.
In my experience, 5 to 20 watts variance (If using single sided) is quite common.
If you have the right time stamp, wouldnât speed be the same, or what source is providing speed for both instances?
dual power pedals - you are correct, it is helpful looking at averages, I just wanted to try and validate the extra watts are not just when coasting.
no, because the power is different - all things being equal, the extra power being applied by the phantom watts are making my avatar go faster than what I should be
I get that, but where is speed coming from for the Assioma graph?