Using Powermeter as power source with kickr


(Lennard Kong tdc) #1

I am using a Quarq as my power source since my Kickr is one of those which reads 25w high.

Erg does not appear to work in this scenario and I have to use the gears to adjust resistance.

Please confirm this observation.

Thanks,

L


(Jon Mayfield) #2

This is unfortunately correct. Imagine in your scenario the workout says to hold 350w.   Your quarq reads 350w, but the kickr sees only 325w, so it will increase resistance.  You’ll end up doing the workout at 375w.

We’ll soon be working on a simple system to try and ‘close the gap’ between two power sources like this to make erg mode a possibility, but right now pairing power and smart trainer ends up disabling erg mode automatically.


(Lennard Kong tdc) #3

Ok, so pairing both disables erg mode.

I believe Wahoo gave the erg software to other companies last year to implement when their overreading bug was brought to light.

TR was able to install it very quickly.

They have never been able to fix it and support emails go nowhere.

I guess I could just bump my ftp up 25w,

will try that and just record the quarq’s power on a garmin and compare later.

 


(Mark Hewitt) #4

Jon,

How does ERG mode work from a developers point of view. i.e. Is it a matter of contacting the trainer to say “Please hold at 200W”, or is it more that the Zwift application itself has to read the wattage and go “up a bit” “down a bit”?

I remember using Trainer Road with my Stages & Bushido combo and it had no issue doing ERG then, of course I stopped doing that as it’s nothing compared to Zwift.


(Lennard Kong tdc) #5

It would be using some type of feedback mechanism in the software

and changing the resistance directly of the trainer instead of depending on the trainer to do so

also with a bit of predictive based on the cadence changes it is seeing.

My main issue with the non-erg mode it runs in with my scenario

is that my preferred cadence is around 95+ 

my ftp is about 250

but I cannot find a chainring combination where I can get resistance of around 260-270 at that rpm.

The closest I can get has me turning the pedals a bit slower at around 88-90 so I have to be careful not to turn too fast and go out of zone 4


(Jon Mayfield) #6

Mark, the command we send is something like “ERG200w”.   How long the trainer takes to go from whatever it was doing to what I asked of it is different for each trainer.  A computrainer might take <2seconds, whereas some Elite units might take 10 seconds.  A Kickr or Tacx is somewhere in the middle.

The logic that does this is in the firmware of the unit and not within Zwift. To do it in Zwift has its own struggles due to latency in the communications, but I think we’ll sort out an experiment or two soon to see what we can do about this.