Watt deficit on short high power intervals


#1

There seems to be a general misconception that “Power smoothing” affects the time it takes for the trainer to ramp up the wattage when you start a new interval. As i understand, this is not the case. Power smoothing ONLY affects the way you see your powergraph. Not in any way how the trainer produces resistance. Someone correct me if i am wrong…

I have ridden two different trainers, a Wahoo Kickr and a Tacx NEO. The Wahoo had a very smooth powergraph (a software thing…) and the NEO a more “jumpy” graph. I can live with the more jumpy graph, but i have not been able to find an explanation for the deficit in watts on a short high power interval.

On the Wahoo, TR told me i was max. 2 watts off after a 40sec. interval. On the NEO i am as much as 20 watts off (330 / 350)… Why is that???..

This is a problem on the short high intensity intervals only. On the longer below-FTP intervals i am only off 1-2 watts as on the Wahoo.

This is probably only a software thing, but does anyone have the exact explanation??.


#2

If you turn off the power smoothing for the Kickr, do you get the same results?


#3

I do not know. I do not own the Kickr anymore. Only the NEO…


#4

A while back, Wahoo had their kickrs set up to broadcast target power instead of actual power. As a result, the power profile was exactly on top of the target.

I don’t know if they have changed away from this or not.

A “real” power profile will look more jumpy.

For the Neo, the gap between rmtaregt and actual average power for the interval could be due to a slow ramp up maybe? You should be able to tell by looking at the power profile.


#5

I’ve noticed this on my Neo, too. For example, there are some 12-second sprints in Clark that are about 3% low. I figured that 3% of 200% of FTP (in Clark) wasn’t enough to worry about. I used Power Match on Clark because in other workouts, my Neo was making me work about 7 watts harder than the target (as reported by my Vector 2 pedals). I haven’t done any 20-second sprints since I started using Power Match, but the last time I did 20-second sprints my average was above the target. So the problem for me only appears in sprints of 12 seconds or less.


#6

The resistance setting on the turbo never changes instantly, it would be akin to hitting a brick wall. It may take 3-5 seconds to get to target wattage during a big interval change. You can help by increasing your cadence before the switch and working really hard to stay at wattage right to the end of the interval, often the resistance drops about 2 secs before the end, don’t slacken but keep pushing to the bitter end.


#7

Thanks so far guys. My NEO vas faulty and i just received the replacement today (NEO 2). Will try things out on that and let you know…


#8

I did San Joaquin +5 on my Neo tonight - some thiry 50second efforts at 130% FTP. I think the closest I ever got was -5 watts; the worst was -10 watts. I was doing everything I could to hit the target without turning ERG off - spinning up quickly just as the countdown timer hit 00:00:02, making sure I kept spinning fast when the resistance backs off before the end of the interval, etc.

I understand that it’ll never be perfect as my power fluctuates up and down through the segment, but I was under for every single rep. It’d be better for them to vary between -5W and +5W, rather than -5W and -10W.

But, at the end of the day, so long as it’s consistent, I’m not really that arsed.


#9

My Elite Direto takes ~10sec for ERG to match the target power. It used to drive me crazy that I was consistently -10 watts below the target power for 1 min VO2 Max intervals, but then I realized that if I just looked at 0:10-1:00 of the interval, the ave power was spot on.


#10

You are right. It is almost consistent and always a little bit under target. I can live with that as long as i am not the only one having this issue. And as i can see, it goes for other trainers as well (the Elite Direto). Maybe i should stop worrying about watt-numbers and just work harder!!


#11

I did Taylor-2 last night which is 45 intervals of 30 secs at 120% FTP (310W)

The majority were only 2-3 watts under target, none were less than 8 watts and a few were on target or over. All using ERG on a tacx flux


#12

Do you have power smoothing enabled on the Direto by chance? It’s an option in the myEtraining app and is set to 2 seconds by default.

The actual power you do won’t change, but the data that are sent to TR will. At least in my experience with the Direto, changes take ~4 seconds to see the actual power get in line with target power. The fact that you’re seeing the power stay elevated for almost 10 seconds after the interval is why I’m asking about the smoothing setting within the Direto itself.