Can't get correct (high enough) wattage especially during short intervalls



If I design a specific workout including short intervals, usually that results in me getting frustrated during that workout.

For example if I design the workout to be 90 seconds @ 500watt and then 180 seconds @ 150 watt, repeat 8 times. When its time to do de 500watt the trainer only gives between 270 and 330 watts. The problem is not only that the watt is to low but that the watt fluctuates, a lot.

Some rides gives the correct watt during the whole interval session, Sometimes it works the first intervals and then looses it’s correctness.

Sometimes it does not work at all…

  • I’m using:
  • A monster pc
  • Tacx vortex smart (FW updated)
  •  Zwift (updatet)
  • Edge 1000 (FW updated) only to log the data from the trainer using ant.
  • Stages powermeter (disabled) during indoor trainer activities
  • Kick ass Swedish legs

Please help. My training program is hurting as I cannot get the intervals correct.



Hi Christian, 

By the sound of it your HUD is showing 3 seconds average power which makes it difficult for you to tell how hard you push at specific moment, please go to settings and change it to instant. See if that helps and let us know. 

Thank you and RideOn!

Thank you for the input. I’ll try it during my interval sessions the coming days. I’ll return with the result. 

I had some intervals in my workout today. Sadly it didn’t work. I checked that the settings was as above. At the 90 sec interval @ 500 watt, the power fluctuated between 300 and 400.


Just to be sure that it wasn’t anything wrong on my trainer or anything else, I rolled to the nearest hill (in Zwift off course) and pushed for a couple off seconds. I got almost 800 watt without going full. You can se that push at the end of the workout (link down below).

So, I believe it’s something in the training mode that does not work 100%. Is it the ERG that tries to adapt in a weird way and fail?

In a interval the output should lock to the targeted watt (in my case in this specific workout; 500w).

Here is a link to todays workout:  




Hi Christian, 

Thank you very much for checking. By the sound of it there is something wrong with the ERG mode. Can you please confirm you have the Tacx Vortex Smart ANT+ T2180 with FE-C update? 

Thank you

Affirmative. FW 3.1.13/0.2.6


Hi Christian, 

Is this the latest version? Are you able to update with your Tacx Utility App? 

And what trainer model do you have? Is it the T2180? 

Hi Tom,


Sorry my answer was a bit unclear.

Yes, I have the newest version of Vortex (T2180), and yes, it’s the latest firmware when I check with the Tacx utility app.






Hi Christian, no problem :) 

In that case you are using you trainer correctly and you have done everything you had to do to make it work. Meaning there is a problem on our side. I just created a ticket on your behalf and one of our agents will contact you as soon as they will find out what’s going on. 

Thank you very much for your cooperation. 

“Thumbs up”!