Power - Kickr Snap 2 vs Quarq DZero

[SCD]

I have a power question to the Snap2. I am using a Quarq Dzero powermeter on my Race MTB. First rides on the Snap felt really heavy on my (powermeterless) trainerbike. I barely managed to push 70% of my normal power. Then I strapped on my Race bike with the Quarq. DCR compared the power readings of various trainers including the Snap and came to reasonably close readings. That is what I wanted to see too. But when measured against each other the Snap power was up to 80W less than on the Quarq (depending on cadence). The drivetrain is ok and maybe could cause a 3-4% loss but not that much. 

 

In order rule out user error I went on and did some investigation. But I am stuck at a dead end. Wahoo or Zwift Spindowns do not seem to make a difference. Using a road tyre at 110psi and 2 turns knob pressure produces a 29s spindown with the Wahoo app. A bit long if one believes the internet forum chats where 9-15s is said to be a good range. The advanced spindown (hidden in Wahoo app) reduces the spindown time notably on the second run but this does not seem to stick. Once the advanced spindown is completed and clicked away it is back to 29s.

 

Racing in Zwift with a power much lower than in real life is not much fun. The only solution that produced a reliable eRacing setup was to use powermatch in Zwift using the Quarq. But that defeats the goal of not using my racebike with the Quarq PM on the trainer.

So question: What am I still missing? What is your average spindown time on your Snap? I would like to see the trainer power reliably within 5% of the Quarq power. Any tips are welcome.

[SCD]

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