Issue with ERG reactivity

Bugs and Issues
#1

Hi everyone,

First post here, first thanks for an amazing training app at affordable price and great community support !

I am sorry if this has been addressed before but I was not able to find a direct answered by browsing the forum. The issue that I am facing is that I find the ERG to be somehow slow to react: it takes 5/6 seconds for the power to reach target. It is not much of an issue for long intervals but as soon as you are hitting high intensity intervals for <1 minutes, it’s not great.

Is there a way to tweak the ERG reactivity to speed-up the servo response on the watt target ? I don’t believe it’s a hardware issue as I am using Zwift Hub and did not have comparable issue when riding it with Zwift (with same gear settings on the bike).

Best regards,

#2

Hi and welcome, happy to have you. Turn off power smoothing in other settings. It’s kind of a bug because the default should be that smoothing should be off.

#3

So if that is off and you are talking about the actual physical feeling in your legs, then ERG trainer control is not very fast, some devices are better than others but generally short intervals are not great in ERG. For under 1 minute intervals it’s usually better to use slope mode. You can read here.

https://blog.trainerday.com/smart-slopes-779c74a0c921

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#4

5-6 seconds I think are the approx time ramp for most trainers.

#5

Thanks for your replies.

I have power smoothing OFF already (tick on the left).

Agree that ERG might not be great for short intervals. I brought up this issue because I feel a noticeable difference between Zwift & TD on that matter. I don’t know if anyone has experienced that before. It is not a critical issue.

Regarding mixed slope/erg mode is there a way to build that in intervals.icu training format or does that only work with the TD editor ?

Best,

#6

Maybe Zwift has some tricks with their trainer. Maybe they even send the signal even earlier to tell it to switch. We send it 2 seconds before the interval which works reasonably ok for most trainers. Since the delay is constant, and you use 5 seconds at the beginning and should gain 5 at the end, the duration should be ok, it’s just your expectations as to when they occur end up being wrong. You can only use our editor to have automated slope mode with our app. If you want to create a feature request to allow slopes from intervals, my guess is others might vote for it as well.

#7

I have the same ‘feeling’ regarding the ERG mode running TD with my Tacx Flux S. Especially comparing it to other apps like Zwift.

#8

Hi Alex, as per your answer I can assume the power smoothing is not just to plot the power curve “smoothly” against the target but also it affect the trainer ERG resistance & reaction.

Just to make my questions more clear, when we ride using power smoothing TD adjust the trainer resistance accordingly to the resulting smoothing then.

Then when we turn it off, of course the chart plot is gonna be as always showing more jig saw shape like line because is showing the raw data but also the trainer reacts faster to the start and end of each interval

Appreciate your answer back since I love the power smoothing but I rather have a more realistic ride and interval start/end interactions

#9

No, smoothing does not affect what you feel. What you feel is the trainer itself. We have very little we can do basically nothing to change how the training feels in this regard. We say Power = 150w now, and the trainer does what it does. We don’t do anything to the power target going to the trainer. Unless you have power match on. If you have power match then that can change things. Zwift might work magic with their own trainer that we can’t do.

#10

Thanks Alex for answering back, so power smothering is just to have a clean chart plotting in the workout display instead seeing raw data jig saw lines (which is perfectly ok for me, I don’t care about how smooth it looks like)

#11

Yes how smooth the line is and how much your current power box jumps around in values. We are going to add more smoothing options now, but if you don’t care I think it is better to turn it off.

#12

Strange, we have a Flux S and it works fine from our perspective. If you could record a video of the screen with you talking and describing what you feel versus what you see it might help us better understand.

One possible explination.
Zwift might create power profiles so they know how long it takes for your specific trainer to react to changes and adjust the offset in seconds to better match what you see.

So for example we send the target change to the trainer 2 seconds before the interval arrives. A tacx neo reacts in about 1 second but a wahoo trainer is 2-3 seconds and other trainers can be up to 5 seconds. So it feels like it changes different compared to the chart you are seeing but ultimately you end up doing the same exact workout other than the whole thing might be shifted by a second or two.

#13

Alex,

In addition to the target you define do you also have a reading of the actual watts on the trainer ?

If so it seems you could play with what you send to the trainer to better servo the real watt on the trainer, using some kind of closed loop control.

#14

Yes I was saying Zwift might do this. Compare how long it takes from the time target is sent to the time the trainer adjusts the watts. This part of our code is already very complex and my personal belief is being off by a second or two is not critical to training but I am also not the one experiencing this. We have not changed this code in 4 years and you guys are the first ones saying anything out of like 20,000 user that have used our app so people with similar delays, I would assume just accept it.

I realized if I could just see a screen shot, you should see it. If there is a delay and the power is happening after the target. Super short workouts like 2 minutes it’s super obvious but since most people are doing longer workouts then it’s not so obvious.

Below you can see my trainer on super short workout. It’s slightly delayed but it does not actually affect the workout. And long workouts you don’t really see it.

image
image1098×1130 96.9 KB

#15

Alex,

Thanks for your answer. As I said, it’s not a big issue I am just feeding the discussion and trying to understand !

I will send a capture like the one you have sent when I do my next training.

Best,

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#16

Since the latest update (the beginning of this week I believe) the response is much faster than before. I have been keeping my eye on it, and it is 3 second on the Zwift hub now.

#17

Interesting. It was modifying bluetooth library. Normally it should not affect anything but you never know. Good to hear.

#18

You did change the power smoothing , am I right?

#19

Oh yes, you can now turn it off in settings (maybe it turned off automatically some how). That might be completely what it is.

#20

No, I turned it off manually. So now reaction time is about 3 sec instead of the 10-15 sec before.
Sorry for the confusion. Maybe my response did not belong here…