Can someone explain this please

[bex]

I have two units, an Ipro and an I aero (for my triathlete wife)
I did coast downs and cal rides for both units, different dates, just for something to do.
I did a 16 mile ride a few days ago and believe the numbers were correct at an average of 215 watts.
I went to tools/switch profile after ride and chose the newer profile from the ipro.
The average watts jump to 583, why is this?
The original aero is .352 and orig fric 7.775

The new (Ipro) aero is 1.144 and fric is 5.454

The only thing different about the profiles is the weather, it was a little windier for the Ipro profile.
Bike, clothing, equipment was all the same.
Why would I get such a difference?
Does it mean I will see different watts if I do that 16 mile ride again but this time with the Ipro?
I am sure I am missing some point here but I do not know what it is.
Hopefully the answer is quite simple, oh and please keep it simple, some of the tech stuff I read on the forum is way beyond my scope of understanding!

Cheers

Bex

[coachboyd]

The aero number is three times greater that your aero number. Chances are that wind scaling is very different between the two units and while cda can be similar, the aero can be quite different. You can't take a profile from one person and apply it to another, it's not just cda and crr that get transferred.

The aero number is what is used for computing power
Wind scaling calibrates the wind port for each unit and is unique to each unit and to position of the unit.

cda is the aero number divided by the wind scaling number. This is the number that most people are familiar with and the number you get in a wind tunnel, but getting the aero numbers and the wind scaling is the important part.

[bex]

So, even though I used the same bike, clothes and equipment and mount stayed in the same place, to create a profile (for me) on each unit, because of the nature of the device, they can give quite different results (for the profile)
Will the power numbers be the same? Or is it more likely I messed up the calibration process?

Bex

[coachboyd]

If it's the same unit in the same position, then the aero numbers should be a lot closer than that. Maybe wait for a calm day and try to redo the coastdowns and cal ride.

[bex]

OK, thanks Boyd.
How would I know then, that I have a good profile if I were a complete novice wanting to start training with power?
Assuming I do have a poor set of cd's and calib ride on the second unit?

Bex
I am a complete novice by the way.

[coachboyd]

You can do a solo ride that starts and ends at the same place and send that file to me and I'll check it for you.

Or to check your calibration on the fly you can go into the setup screen, scroll to the coast part and coast at about 25mph. Your watts on that screen should read +/-20 watts. If it's above or below that, then your profile might need a bit of tweaking.