Is there a design for when an ERG takes off the target?

I did Torque Monster and forgot to change from ERG to Level mode. I was pleasantly surprised when I got to the first big effort that I was able to blow past the planned watts number. Second effort, same thing. From there on however the watts were capped at the planned level.

Yes I know I could have gotten off my bike and changed to Level mode but that is not my question. Is there a method to the times when the program ‘unlocks’ the watts numbers for big efforts in ERG mode or is it just random, or is my instance just odd and it is not designed to allow it ever?

1 Like

I’m guessing that’s an error. I don’t believe ERG mode is designed to ever allow you to significantly overshoot or undershoot the set target.

3 Likes

When there is a rapid acceleration in flywheel speed either from changing up the gears or increase in cadence, its possible to overshoot the target wattage in ERG mode before the trainer can back off the resistance. This is exactly the situation for the 1st interval in this workout where you start from a standstill. My guess would be that after the 3rd interval you’d lost some of the “snap” in your legs and ERG mode was able to keep up with you.

What trainer do you have?

4 Likes

Agreed - this happens to me - usually at the start of the interval and when I get ahead of the cadence target before the power target changes.

1 Like

I was pushing 300 watts over target so I would call that significant, intended or not.

Not sure this is accurate from my experience. It seemed to hold to the target for at least 10 seconds and then ‘released’ for lack of a better term.

I am using a Wahoo Kickr Bike.

As I stated above, this occurrence seemed to be later in the effort, not right as I ramped up.

There have been several instances on rides in ERG mode where this has occurred. Also worth mentioning is that this is my second Kickr bike, my first had to be replaced, and this has occurred on both, albeit infrequent.

Thanks for the replies.

Yup I can do this on the Tacx Flux as well. Sprint endings on races are often set at AC power but I push NM and go well over the target power and finish the interval before Erg can do a thing to slow down the fly wheel. You can stay ahead as well by ramping up too.

3 Likes

BOOM!!

1 Like

If the trainer is operating properly as you pedal harder, resistance decreases to maintain the target power. The usual thing is resistance decreases and you have to increase cadence until cadence becomes the limiting factor. If ERG mode worked perfectly, you’d never be able to do anything other than the target power. As pointed out by others, you can cheat for a short while because of the inertia of the system and lag in response.

2 Likes

It happened again and this time I was paying strict attention. I was doing Cadence Builds which has 6 - 30 second cadence rump ups. In the first five it held me to the power limit for the first 18 seconds and then it ‘unlocked’ and my watts jumped. The final effort it did the same thing except it ‘unlocked’ after 15 seconds. Truthfully the first one caught me by surprise so I didn’t really push it. The last two I pushed hard.

Some had theorized that I jumped out ahead of the program but that is clearly not the case. It allowed the higher watts at the back half of the effort. Here is the graph from todays ride.

1 Like

To answer your question in the title, I would say no. Nothing built by design to allow the target to be exceeded (as significantly as you have) whilst in ERG mode.

Your latest ride Power profile does not look correct having been in ERG mode. I did this yesterday too and it doesnt anywhere near reflect what you show in the graph.

1 Like

I’ve always found that I exceed power targets in erg mode when I increase cadence quickly. As soon as my cadence stabilizes, does the power. During cadence build drills, I usually increase cadence consistently (and quickly) throughout the interval and consequently see very high power readings. I have two KICKR v5s and it happens on both. I think what’s happening is that the KICKR is constantly adjusting resistance to try and match the target. However, there is necessarily a delay. Even if it uses power from half a second ago to adjust, when you ramp up cadence over an interval, the adjustments will always be too small. I don’t see anyway for the machine to avoid the phenomenon.

Edit: one more thing. Make sure you have the latest firmware. A number of months ago, Wahoo released an update that corrected a gross over-estimate of power at high flywheel speeds. The same update also improved cadence measurement at high cadences, although it still has a lower limit than most external sensors.

1 Like

Hey Sir @Critmark, you’ve got the Kickr Bike now right? I thought there actually was a limiter on the bike to “limit” cadence to a certain RPM ceiling by increasing resistance.

Yes I do have a Kickr bike. I am not sure that the bike limits cadence, but I do think it does limit the display of cadence. I know I can hit around 130 rpm and the display does not go up from there, but I can spin faster. My perception anyway.

I’ll often exceed the power target in ERG mode doing cadence builds. My trainer goes down to minimum resistance (ERG mode doing its job) as I build up the cadence, but then the trainer cannot reduce resistance any further to account for additional increases in cadence. I could change gears, but the I’m not too concerned about being above the power target for a short while.

I think the limit is on its ability to measure cadence accurately. My experience, with the most current firmware, is it can measure up to about 165rpm (if you keep a pretty smooth pedal stroke—perhaps it would be higher if my stroke were better).

How old is your KICKR Bike? I bought mine in Oct 2021, and I read that the cadence was capped at 130. I do recall thinking that while I could push it up a little bit above that level, it didn’t seem to give reliable numbers.
Fast forward a few months of working on cadence drills, and possibly a firmware update to the KICKR, and I now feel that it reliably records cadence to at least 150 rpm. Above that it, I’m not reliable enough at pedaling to judge.

I have a direct drive KICKR v5, not the bike. The firmware update several months ago significantly increased the rpm it could measure.

The Kickr infers cadence from sensing torque pulses. If you produce two distinct torque pulses per rev while pedaling, it can read cadence. If you don’t, it can’t. Normal pedaling under load generally works. When spinning at very high cadence , or when reducing cadence with the flywheel having to slow, it often doesn’t. This isn’t a flaw, it’s a fundamental limitation of how it works. For me, I figure it’s worth the relatively minor expense of having a dedicated cadence sensor.

1 Like

I believe that at the start of each separate interval within an ERG workout, a one-shot command is sent to the trainer to tell it to hold X power. The internal electronics of the trainer then attempt to maintain that fixed power target until the next interval target value is sent. The software (SYSTM/RGT) has no control over the trainer during the interval.
Think of it a bit like the cruise control or speed limiter of a car - if you put your foot on the gas you will override the set speed and the control won’t be able to bring you back to target until you ease off. Maybe not the best analogy, but it’s the first one that came to mind :wink: