Indoor course. Too low speed compared outdoor.

Have you calibrated the trainer in the Tacx Trainer App and / or Garmin?

I have a Tacx Flow (wheel on) "smart" trainer and am generally pretty happy with it as a means of getting exercise but I have a similar issue to you in that the ascents are very optimistic maybe by 50% compared to following a previous outside course / ride, I am just not that good on hills while the descents & level riding feels much harder than outside. I can understand that it can give no gravity assist and downhill will be at 0% grade regardless of the actual negative grade is but the level (ie 0%) feels hard.

Calibrated ok frequently via both the Tacx Training App and the Garmin, I also have difficulty in getting to the required 32km/h but the calibration makes no difference. I have just come to accept this as the Flow is the cheapest smart trainer and still gives a good workout.

I have seen reputable reviews that say indoor courses / rides on the Flow compare well to the same outside but this has not been my experience.

Mmmm i will check that neo2t calibration...in fact i think ive never found that section since i bought it... i think that riding this indoor (originally outside rides) are the only moment where you can "check" the trainer capability simulating the real life. ...so in that flat sections is where i found a gap.

Yes..you are right...tried but no place to calibrate it as Rouge advice me. Same "watts"  (in fact i dont know if they are the same as my power meter may be different from tacx) same place... outdoor speed 33....indoor speed 29...

Outdoor flat speed doing 200w in my mtb is around 33kmh and i can "easy" do that....  in the same track sector in the indoor is very hard to achieve 33..maybe in the 240w zone.

thank you.

kdx200

You cant go 33km/h @200w with MTB (what tyre? 2.25" dirt or semislick road tyre?) , only in tailwind. With road bike is possible but on drops and not on hoods. Usually the rider is weaker inside a bit than outside, lets say with 10-15% apprx at 1st tries (i mean if you measure your power with same powermeter inside and outside , then outside you can hold 300w for an hour, inside only 270w due to the higher core temp and more humid air/less oxigen), depending on cooling, air change, humidity, etc. With lots of indoor practice and equipment/enviroment optimization you can improve your indoor performance close to the outdoor one but will be a bit weaker, 1-3% diff apprx. 

The other problem could be if your Neo2T underreports the power due to wrong factory calibration, not so usual but happens (as some 2Ts overmeasure). If You have dual-sided bike powermeter and that is validated and accurate, You can compare the 2 devices, must be within 2% (bike powermeter should be above with 1-2% than Neo)

And your bike powermeter also could underreport your power (this 200w 33km/h with mtb is suspicious) and what You think is 200w is 250w in reality outdoor or more. 

Ok, i will check my outside power and re calibrate the pm if needed.

Also and not taking account power figures, the fact is that iam doing less speed indoor with the tacx in the same track sector with the similar perceived effort. It is more than the 10 15% you said. 

Thanks for you commitment