low wattage with calibration ride & coast downs?

[ScottChapman]

So, when I got the new universal mount I went out and did a good calibration ride and a ton of coast downs.

But when I took it out for a couple of rides the other day (very hot and humid days) it felt like it was registering low wattage. Sure enough, when I was done with the ride and looked at the data file, it appeared to be somewhere between 20-30% off.

I re-applied the quick-start profile I created before doing the calibration ride and coast downs and that seemed better...

[jslopez93]

Curious as to what numbers are you seeing if you just go to coast down window and not pedal?

[ScottChapman]

You mean what wattage does the head unit show while you are coasting on the bike not pedaling? SInce I have a cadence sensor, it shows 0Watts.

But I suspect you mean something else?

[bjrmd]

I wonder if something is wrong with the algorithms in either the pc software or the Newton.
I have a thread on this and no one seems to be commenting on it
I use a Powertap so the accuracy is secondary but it would be nice to have it working properly
I have been getting excellent correlation between Powertap and Newton in the Isaac software though.

[Velocomp]

Please post ride files

[ScottChapman]

Here is my ride (it is actually two days ride).

[jslopez93]

Coast down window is under Set up/User, keep pressing down till you see coast. Don't press the middle button but try to see what your power numbers look like when not pedaling.

My experience with coast down window and not coasting is that I'm usually at +/- 20 watts on various speeds/terrain but am still a little skeptical on numbers as it's been noticeably easier to hit higher numbers lately (with same perceived effort vs. gen 3) so I wanted to differentiate actual vs artificial improvement.

[Russ]

With the cadence sensor, you can also soft peddle, ie turn the cranks at somewhat lower rpm than would apply power. The iBike then records the power it computes and shows it. Usually it will be near zero and maybe bobbling up and back to zero if all is near perfect.

If all it shows is zero, then something is off, if all it shows is excess power then something is off. Something could be wind scaling, cda, crr, tilt, weight, ie just about anything.

If things are normally in the ball park, and wind scaling and wind cal and tilt are good, then probably cda or crr.

Regards,
Russ