Direto XR problems with ERG mode

[jhankey]

There is a significant difference in the tracking in ERG mode when using my etraining and a zwift profile.
I'll generate two ride files, one from zwift and one from my etraining with the same intervals.

On a note on cadence variation, it is a little chicken before egg. If cadence increases,resistance has to be decreased for the same wattage. If resistance is changing by a value greater than expected, by causing a 10w+ variation, this will definitely cause a cadence change in the cyclist, particularly if it is a fair effort. The question is which change is driving which. There could be a point where the sampling of the rpm, the change in resistance and the natural human reaction time to the change emphasises this issue. I should hope elite have tuned this out.

I think the units are probably too good. But there must be a compromise as others have done it.

But honestly, it is unusable in zwift erg mode.

[Elite Admin S]

Hi

I'd like also to add one little note that may help you to minimize oscillations.
In ERG mode, using your small ring on the front chainring is highly recommended. Fluctuations increases if you use the large ring.
So guys, try also this if you want to see less fluctuations.
Also DC Rainmaker talked about this point recently in a comment to his review of Direto XR.
Here's a link to the discussion:
https://www.dcrainmaker.com/2020/07/eli ... nt-3647601


@Ernesto,

Here's one of your trainings. Oscillations are around +/-10W, but in some points +/-20.
If you notice, the oscillations are higher when cadence is less stable:



On another training you've sent, oscillations were bigger but speed was quite unstable, here I've changed the scale so you can see the speed:

[enesto]

First chart, where you're underlining that the oscillations are +10+20 is taken from the data with power smoothing 10 of my file (we all have already said that with PSmooth at 10, things are going better.

Second chart, you are underlining that scattering is higher, is made using the file I've sent with smoothing 2 and this, again, is exactly what we are sayng here.

But, in the second case, you say it depends by a not stable cadence/speed.
How the speed is computed?
On a real bike the speed is distance covered by the wheel in a certain amount of time right?

The distance is the number of rotation of the wheel * wheel size (set in the app = 2070mm)
Number of rotation comes from chainring / rear cog (34/16) multiplied for the cadence.
So, standing at cadence of 80 rpm it should be:

34/16 = 2.125 (every pedal complete turn, the rear wheel makes 2.125 compete turns)
2.125 * 2070 = 4398.77 mm we can round it at 4399mm = 4.399 meters.
At cadence = 80 rpm --> 80 * 4.399 = 351.92 meters
So it means that in one minute we have moved for 351.92 meters
This corresponds to a speed about 21km/hour

Right?
This is math... no doubt about this.
In addition to this, in real life, we can have drift effect, or negative slope that, in certain condition can grant you to keep the same speed even if your cadence drops to 0, and you will probably reproduce this in your equipement with some additional computation or math modeling...
Don't know how this has been modeled during a workout in MYET.

Now, the trainer is not moving, so we can check the cadence and apply the cadence to the gear used (again 34/16 fixed in my test) and the wheel circumference set in the app (2070)

Now, as you can see from my charts below, comparing my cadence in the two files I've sent, with the exception of some spikes (some under 78 rpm and over 81) I would say that the cadence is quite enirely included in 78-81 rpm and speed is included in 21-23 km/h.
78-81, on an average of 79, I would say it's the normal resolution of your internal cadence measurements 1/80 = 1.25% accuracy that is more or less the accuracy of any other cadence sensor...

Just to have some % these are the real values:

Smooth 10 test:
Number of observations 696
Less 78 rpm 27 observations = to 3.88%
Over 81 rpm 16 observations = to 2.30%
Between 78 -81 653 observations = to 93.82%

Smooth 2 test:
Number of observations 694
Less 78 14 observations = to 2.02%
Over 80 7 observations = to 1.01%
Between 78 -81 673 observations = to 96.97%


I would say that, between smooth2 and smooth 10 test there is no big difference, and probably, during the smooth10 test, I had a worst cadence stability, but this translated in a better/lower scattering in power values.

So you're still convinced tat a 97% of cadence included in 78-81 rpm over about 700 seconds of observations is not a stable cadence. Really?

And again, smoothing 10 is giving low scattering because the values you're logging are not stable, and an higher smooth value is adding a sort of compensation.

I'm not the only one concerned about this, you can check it on FB Direto X etc. Group, in these last days, other people are asking the same things I'm asking here.

Last chart is confirming what I'm trying to say.
Blu line is the difference between cadence from one observation to the next, orange one is the same, but for the power.
Grey line is the actual power otput
You can easily see (I've just selected from 500 to 585 observation just to zoom in excel, in the middle of last 150w interval) that cadence is moving around 0,+1 -1 while the power has movement of + - 40w)

Doing the same with smooth 10 gives best results, you can see orange and blue line are quite completely flat, and the grey one is less scattering + - 10W)
This behavior is spread all over the file.

Again, if everything's normal and these are the results of the Direto XR in ERG mode, I'm fine with it and all other people with my same doubts should do the same.

[magnus.arlebrink]

My new XR has the same issue. I’m only using My E-training app for the ERG functions. My first workout was 2x20 @ 250 watts. But I thought the wattage felt strange and realized that it was changing between 220 to 300 watts. The raise in watts is sudden and very noticeable. I started to look at the wattage and the rpm for cadence. Although I did my best to keep a steady rpm I saw that the cadence data also were changing. Much more than was perceived by me. So, I thought it was an issue with the power/time ERG as the resitance has to change according to the cadence. I thus went for my second training session today, using the slope/time training program. Setting the slope to 3%..To my disappointment it had the same issue. The resistance is not smooth over time. The change is very noticeable...How do I fix this?

[imarszi]

+/- 10W is OK
I have +/- 100W. This is totally unacceptable and therefore the ERG mode cannot be used. In resistance mode, I can keep the power constant.

[enesto]

Hi imarszi and magnus.arlebrink,
I really don't know if this is just a case, or maybe I'm trying to convince myself
I've setup the wheel size, in My Elite training, to 171 (changing the default 2070).
This setting should be used to link the trainer to bike computer like garmin, bryton etc... (at least this is what I've seen in GPLama review 2070 / 12.1 = 171), but it seems to improve the results, even if my cadence, in this test, it is not really steady as before...

Here it is a workout in zwift and the values seems far better than before, not really clean but the average spikes are aroung 10 w or lower...

I cannot find a reason, but it seems to be better... may be you can give it a try and let us know...
Hope this helps in some way...

E.

[jhankey]

Enesto, I will try this tomorrow also.
Did you have smoothing at 2 0r 10.
That graph looks totally acceptable.
In free ride mode I have really got to enjoy the response of the direto and it's feel. If this resolves the erg and erg control mode issues I will be massively happy.


Might even go try this now!!!

[jhankey]

Everyone. GP lama has done a review on a crank power meter today.... in his larma lab he tests it against pedals and Direto XR.
here is the link https://www.youtube.com/watch?v=yM0LuAI70v4 watch it 13.00 in.
The direto trace is flatlining in erg mode.... not what we see at all.

[BelgianFlandrien]

Hi all,

I'm having the same problem. Coming from a Wahoo Kickr Snap (wheel on) I expected way better results from this premium direct drive trainer.

One thing I noticed was that both DcRainmaker and GpLama had an update after unboxing their trainer. Both times you can see they are updating to version 068. When I check for updates, it shows version 067 is the latest and no new updates are available. Are they on a beta-schedule or is there something wrong with my Upgrado app?
Anyone else "stuck" on firmware version 67?

[jhankey]

Good spot BF...... mine is also 067.

Elite Admins .... can you come back to us all on this point!!!!