Mystery of the missing watts

[geoffsuperturbo]

i went out to do another fitness test on the training bike with GEN3 pro clamped to my tri bars. i rode an out and back . what i didnt really take into account was the resurfaced road is very rough and may cause problems for the ibike.

i started the test with a huge tailwind. i was pedalling as hard as i could but hardly getting any power on the display. i soon worked out the vibration of the bike on the very rough chippings in the first 2 miles was messing up the ibike . when i got past the bad chip road the ibike started to show more constant wattage, but the average power on the ibike was reading around 90 after 5 or 6 minutes so i was sure of another failed test.

i got home and downloaded the ride, and found that when i analysed the route the power miraculously shot up to 305 watts from a rather disasterous 214. i am wondering is this 305 as accurate as i can get or is there more can be done to tidy up the bad readings throughout the ride?
i was also amazed no vibration showed up on the tilt plot, but the ibike obviously wasn't reading power well at all in the early part of the ride or later when i hit bumpy road again.

i attach the file of the fit test and would appreciate an expert running an eye over it and making any adjustments to get an accurate power measure for the test. i admit i may not have paced the ride too well as i tried a bit too hard early on to try to raise the wattage. the power does ease off a touch at the turn where i had to freewheel slightly around the roundabout.

[geoffsuperturbo]

at times on the graph the power drops to 0 in the first 2 miles and stayed there quite a while, this must have an effect on the average watts and i presume on normalised watts too. in between those 'negative power' spikes i am quite constant at around 320, so i am wondering what i can do to erase that bad data, there doesnt seem to be anything in the software to get rid of drops in power on the bumpy road, or high power spikes.
i have now moved the ibike onto the stem and am hoping this problem will not be so bad as all my testing courses go over that piece of road , and many training routes.
if the ibike can't handle rough chip roads then it becomes a useless training aid, i may aswell go back to pulse

[Velocomp]

If you switch your bottom axis to Time, you'll see that your watts were low for the first five minutes. This is because your "riding tilt" in your profile is incorrect. Riding tilt is measured in the cal ride. After the first 5 minutes you'll see that your power becomes much more normal, because the Gen III has figured out that your riding tilt is incorrect, and has applied a correction.

But there is something else very odd in your ride file too. It shows a huge tail wind on the out portion of the ride, and only a slight headwind on the return portion of the ride. The average wind for the entire out-and-back ride was a significant -4.5 mph. So, your Cal Wind was incorrect for this test. NOTE: for good fitness test results, your iBike really has to be calibrated properly!)

Here's what I did:

1) I returned your ride file to its original state with the "Tools/Return to original download" command. This unapplies all fixes

2) I applied the "Tools/Analyze Route" command. This tool fixes the problem with your 5 minute riding tilt, and the problem with the Cal Wind. I assume your fit test included no drafting.

The results of this effort are 304W--not bad! You'll also see that the first 5 minutes are correct, too.

We are working on, and will VERY SOON have completed, the "Boyd in the Box" wizard that will find and correct these kinds of problems.

Also, note that there is no evidence of vibration in the ride file. This is not a problem caused by chip seal roads...

[geoffsuperturbo]

oh i see, it was just coincidence that the power began reading normal when i got off the bumpy road?
it seems odd as the power was ok warming up, it was only when i got up to full speed on the bumpy chipped road that things went haywire, it feels like cobbles to ride on. things were still going wrong when i hit bumps on the way back too which can be seen on the graph. a couple of times power just drops off for no reason, it was a hell of a wind believe me i was pushing hard the whole time. only after i got off that road was power constant, that is why i was amazed to see no evidence of vibration on the tilt plot


i dont know why the wind was out, i left the unit outside to cool down before i set off , and i did a wind calc after 2 or 3 miles of riding, in fact 2 as i thought a gust of wind had messed it up. i also did 3 tilts until i got what looked like a good result. so i dont know why it all messed up. i hope i dont need to do a new cal ride as after analysis the power seems to be accurate. i got 306 watts when i analysed the route, which i'm happy with at 4.3w p/kg. does that mean my ftp will be 304/306 or do i put 95% of that number in the ftp window? the ibike worked out something like 2.9 w p/kg from the test, but i want to use the inbuilt training routines so i need an accurate w/pg to get the correct intensity of workouts.
thanks for looking at the file

[Velocomp]

Use 95% of your average power to get FTP.

Your ride file shows things returning to normal at the 5:00 mark. Your ride tilt is incorrect. It may be coincidental but it is what it is...