ERG mode with an external power meter difficult to keep watts consistent.


(Jessie Wagman) #1

Hi,
I recently have done a workout in workout mode with my stages power meter, set as the power source paired with my wahoo kickr snap as the smart trainer

During the workout it was pretty difficult to keep on the target watts. My watts would fluctuate from the target power to + and - 20 watts.

What it felt like was happening is that my trainer would change resistance according to my power meter, making it harder or easier consistently, making my power jump around even though my cadence generally stayed the same.

Is this something that I am doing wrong? Is there a way to make EGR mode a little more consistent with a power meter like EGR mode with a smart trainer as the power source?

As a side note, I am pretty good at keeping my watts consistent outside of Workout mode.

Thanks!


(Nigel Doyle) #2

Have you got 3 second smoothing enabled in the settings? Oscillating over and under the target power is normal. With luck the average power for the interval will match the target power.

The main thing for consistency is to keep your cadence steady.


(Jessie Wagman) #3

I will have to check with the 3 second smoothing, but my cadence is pretty rock soild, I have a ton of roller training under my belt and can keep my pedaling super smooth, so I would like to think that isn’t the issue.


(Roger Pier - CISCYCLING) #4

I’ve observed the same thing. I am also using a Stages power meter and using a kickr (direct drive). The watts tend to move around a range and can at times go over before trying to settle down to the general wattage. I have 3 second power on, but this should not make a difference in the target wattage. 200 watts should be 200 watts, not everything around it.


(Jessie Wagman) #5

What I don’t understand is why its changing so much when my cadence is steady. By my understanding EGR mode ignores the gradient change. So if my cadence is unchanging my power should vary minimally. The resistance should only change when the target watts change.


(Cary Sporinsky TeamZF ZHR(F)) #6

You bring up a notable bad point about ERG mode. I can hold a w/Kg average very easily when in Sim mode, yet forget it in ERG. I think ERG mode is designed to piss off a rider so much they get a much greater HR workout. Sort of a stress simulator. You think I’m joking…


(John Binns) #7

Yes me too. I’ve experienced this with my Kickr Snap and an external power meter (Favero Assimoa). I wonder if there just a bit of lag between the power meter and the kickr controlling the resistance to equalise out the power. 

I’ve got a lot better at keeping cadence steady and it’s rare now that I don’t get the star for each bit of the workout. I think it is impossible to not go into the red (under or over) for for a short time. So it’s not much of an issue any more for me at least.

An external power meter is probably much better and more sensitive at measuring power than the one built into my trainer so I’m guessing that power  jumps around a lot for this reason. For rides outside it is a very similar behaviour. 


(Leanne Arnott) #8

(Anthony Heyward TeamZF/Cardiac Athletes) #9

Hi All

Thank you for the above, I too have had the same issues using my Stages as the power meter.  I definitely agree with Cary about the stress test!   Constantly chasing the correct wattage made it a not so enjoyable ERG Session.  I’m hoping Zwift maybe able to provide a work around this in the future.

Ride on.


(Bruce Malarky - LaGrange) #10

I did some experiments recently and tried many configurations (Zwift on Apple TV with Cable ANT+/BT device, BT only and via ZML, Zwift on Mac using ANT+ adapter or BT only.) I used the Weav Run program to get a steady music track at a specific BPM/cadence. During a structured workout the Zwift power reading and resistance go up/down giving constant advisories to use more/less power so I ignored them and concentrated on cadence. Unfortunately, with varying resistance it’s much more challenging to maintain a steady cadence. My next experiment will be to use a dedicated cadence sensor and ignore the Stages power/cadence. The other possibility is to adjust the trainer difficulty and see what happens. I think the best configuration so far was ANT+ to Zwift on a Mac but it wasn’t rock steady. Hopefully there’s a magic mix.


(STEVEN NADLER) #11

I have similar issue as follows: I use Trainer Road for erg based workouts, with Stages Power meter and Kickr (2d generation), with Stages power meter “controlling” the resistance of Kickr. When I start a new interval that is a big step up in power, there is a large overshoot (at times 20-25% higher power) that lasts for 15-30 seconds, then power comes down below target, then eventually settles out albeit with lots of up and down variability, that is easily sensed as I peddle.  It is a major issue, because if I am doing short hard intervals, I end up having to put out power way above target, leaving me exhausted before end of workout. Also, because of large overshoot of power, my cadence falls off and that makes the issue worse. HOWEVER, I have a separate setup using Trainer Road, Kickr (First generation) and Power2Max power meter, and when using that system, there is RARELY such an overshoot, and the power variability during a fixed power interval is incredibly minute and I am certainly not able to sense varying power while spinning. I would ove to be able to get rid of the overshoots with my first setup, so any ideas are welcomed! Steven


(Alfonso DeLuca) #12

You know, I just tried my stages PM Gen 3 & am having the same issue. Is it a Stages thing or Kickr thing?


(Sierra Ryland) #13

Hi there,

Mine is doing the same thing with an Elite Drivo. It didn’t always do this but the last couple of rides it keeps increasing the resistance and makes it so hard that I can’t peddle. Does anyone know how to fix this? 

Can’t really do the training rides and meet the target power numbers if the resistance keeps randomly changing.


(Mark Duchesne JAM Racing) #14

Yep, I have just tried to create the same setup on my kickr, I use a infocrank powermeter to control my kickr. 

 

For a 57 minute race the other day the zwift normalised power was 250 Watts vs 240 watts which I guess ain’t that bad. The watts tended to deviate more on the climbs and harder efforts which from reading these posts seems to have something to do with the change in cadence??