Hi there, first time posting!
In an effort to be more transparent/check my smart trainer isn’t wildly out, I’ve started to try and dual record my rides, using my elite direto to Zwift, and 4iiii PM to my Wahoo for the second recording.
When trying to line up the graphs to match the data, I have found something a bit odd!
It seems that the data from the smart trainer and the data from the PM slowly start to diverge on the timeline. For example, I have cropped to adjust for the fact I started my Wahoo 9s late and at the start of the gran fondo on Saturday, the power numbers match up. However the further I go into the ride, they slowly started to diverge and by the end, the 4iiii-Wahoo combo shows my ‘final sprint’ finishing at 2h28min8s, but the corresponding spike on the direto-zwift is almost 45 seconds earlier at 2h27min26s! I seem to have lost 42s of data somewhere compared to the powermeter! The 4iiii data corresponds much better with my ZP finishing time for the event. I can get the data to match up if I change the offset for the direto but then it means it is then not matched up at the begginign of the ride! Somehow it has compressed the data to seem like I have completed it nearly 45s sooner?
Interestingly, I have noticed that I also ‘lose’ about 15-20s an hour when doing structured workouts, in that despite setting a workout for say 1 hour exactly, I complete it in 59mins45s and I start noticing this from about 10 minutes in that the ‘time completed’ and time left’ starts to mismatch.
I am on an apple TV 4th gen set up. I had a look through the forum and it seems the workout discrepancy has been raised before but can’t see any answers.