I just bought the Tacx Vortex and been using it with Zwift for past couple of weeks. I use a Garmin 510 but do not use a power meter. Have to rely on the virtual power meter.
It seems to me that my power output is very low for the effort I am putting in - particularly on the flats and downhill. Hills are a bit better. But it’s making taking part in the group rides very difficult indeed.
Any suggestions? Is there a way to calibrate virtual power or Tacx?