DFPM and iBike power difference in short efforts

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doofus
Posts: 60
Joined: Sat Nov 29, 2008 10:00 am

DFPM and iBike power difference in short efforts

Post by doofus »

I haven't had a good non-windy, low-traffic day to do a DFPM cal ride with my iAero, but I've done a few outside rides with it and the Power Tap Pro+.

Easy level 2-3 rides, the watts are very close -- the iBike a little low, but within 10 all the time.

I did a sweet spot ride -- 45min averaging 315w, with :10 jumps thrown in every 5 minutes or so. I notice the power difference on the :10 jumps is big -- enough so that the two ride files have pronounced NP, AVG P, and TSS differences.

Anything to fiddle with here, or is it just the nature of the unit that it works better for longer efforts (anything longer than a sprint)?

I really, really, like the iBike as a head unit -- I'm glad I went this route last fall rather than getting a Garmin.
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coachboyd
Posts: 527
Joined: Thu Mar 27, 2008 7:01 pm
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Re: DFPM and iBike power difference in short efforts

Post by coachboyd »

Because of the side to side movement and the way that you point your handlebars down in a sprint, the iBike can tend to under-report wattage for short bursts. We are working on a fix for this and I'll be testing it out probably very soon.

I did take a look at your profile and edited it a bit to match your power tap. There is a moment at around minute 41 where you see the wattage vear off for a bit and then jump higher. I'm not sure why this is. It could be the slope catching up with barometric pressure, or it could even be the power tap slightly drifting the torque during the sustained effort. I don't know how sensative the electronics inside the hub is to heat build up from continuous efforts like this.

Anyway, here is a revised profile to get you more in line with what the power tap is telling you.

Boyd
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Boyd Johnson
http://www.boydcycling.com - high performance carbon wheels and accessories
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