Wattage discrepancy Jetblack Z1 vs Wahoo Kikr


(Alain Menager ZHR (G)) #1

I have been using Z1 for almost a year on Zwift (since the early Beta days) and according to Zwift ended with an FTP of 301.

Now I am 57 and stopped racing about 3 years ago so I always suspected this was an overly generous FTP and my cruising uphills made me think I was either superman or everyone else must be weekend warriors at best.

Last week I finally got the funds together for the Wahoo Kikr SNAP and not only was I not able to hold 300watts, I could barely even get to 200… anything over 150 was serious hard work for any period of time… On the Watopia island EPIC KOM I went from getting to the top in 24 minutes to needing over 50 !

Is it that Jetback’s power curves are completely wrong or is it that Zwift is misinterpreting the data. How can there be close to 70% discrepancy between Z1 and Wahoo power?

Perhaps Zwift could display whether someone is riding smart or dumb trainer to give a bit more reality to the whole experience.


(Cleve Waterman 69y/o) #2

My recommendation is to carefully perform the advanced spindown.  Decide beforehand what tire pressure you will use each time. Also, put a mark on the rotary knob that adjusts roller tension. Tighten the knob till the roller surface just makes contact with the tire and then give exactly 2 more 360 degree turns. The mark on the knob will help with the exact turns. Zwift should not be running when you use the Wahoo app to perform the spindowns.

I have noticed lately that I have trouble sustaining my usual effort.  I hope it is just because I have been riding a great deal and need some rest time.


(Alain Menager ZHR (G)) #3

Hi Cleve, thanks for advice, you seem to think that the problem is with the kikr calibration rather than the Z1. I will recalibrate and see if that makes any difference.

cheers

 


(Cleve Waterman 69y/o) #4

I did another basic spindown today and then did a set of VO2-Max intervals. I experienced the appropriate amount of agony so I think everything is working correctly.  I am happy with my Snap. Good luck!


(Alain Menager ZHR (G)) #5

Well I redid spindown and then also experienced the right amount of agony but my wattage showing on Z1 was on average about 100 watts more than with Wahoo… I suspect the Z1 displayed power was highly inflated… Not sure why Zwift can’t get the Z1 power sorted.


(. TomH..) #6

Hi Alain,

We’re sorry to hear you’re having some troubles there. 

 

  1. Wattage difference -  virtual power on a classic trainer will never be as accurate as power meter or electronic trainers with highly accurate power curve like Tacx NEO for instance. However if the numbers you’re providing are correct there might be an issue and I will raise this issue internally.
  2. Wahoo KICKR Snap calibration - Wahoo is recommending to do the standard spindown every time you use it for accurate readings. The advanced spindown only needs to be done once when purchased or every time there is an error during the regular spindown.
  3. Dumb vs Smart trainer in Zwift - You can tell who is using a smart trainer or standard trainer by looking at the lightning sign by the rider’s w/kg value. See the picture below.
  • Lightning sign = power meter or electronic power curve (Smart trainer) 
  • No sign = Standard/classic trainer with cadence and speed sensor. 

I Hope it helps and Ride On!