Weird blocky power output for speed + cadence

So I’ve not (yet) forked out for a power meter, I come from trainer road which I’ve never had an issue with in terms of getting virtual power, so I have something to work from (even if it’s not 100% accurate).

Here is my setup:-

  • Race bike
  • Samsung galaxy S9 running Zwift app
  • ANT+ Garmin speed & cadence sensor 2
  • Kurt kinetic T2200 dumb trainer
  • Garmin ANT+ heart rate monitor
  • Wifi connection to 100M fibre broadband

Everything is working ok except the power output that is calculated, I’ve attached the Strava activity pushed from Zwift, as you can see all data sources are working ok expect the REALLY blocky calculated power output.

I will cycle and it will sit at the same power (say 171 watts) despite small changes to my speed (which should then make small changes to my power output), but I will get these really big steps up & down which makes for an unusable experience as far as Zwift goes. Trainer road does not have this problem and I get nice, smooth calculated power output.

I could understand if for some reason the speed was also blocky, but it’s not, so I don’t understand why it’s like this, unless it’s on purpose (give you rubbish data to push you to get a real power meter).

I’ve taken off the mobile cover, made sure there are no signal issues by having my hardware garmin open as well, and you can see the speed data is fine. I’ve also tried all combinations of class, zpower, instant and 3-sec average power outputs.

Does anyone know if this is intentional or if there is a known fix for this?

I will get a power meter some time down the line when I’m fitter, but for now just want to get some usable power data and not this blocky mess.

I would upload images, but this stupid forum software won’t let me upload or even link to images, despite providing a function to do so… * slow clap *