Question Wind scaling values

[speedracer]

Since the value for the wind scaling seems to influence the overall power on flats and descents most I have still the question what is the best value to use.
@John: You mentioned that 1.7 is best for Garmin combo mount and 1.4 for the mount you ship with the PP (handlebar mount).

Why do those values so much differ? 1.4 to 1.7 is quite a difference as I noticed.
I would assume that the PP mounted in front of everything (Combo Mount) would cause that more air is coming into the PP mouth? Why then the wind scaling value is higher? Or am I wrong?

After you adviced me to switch to 1.7 for my setup with combo mount I changed the value accordingly (before 1.6). Now the values seem to be a bit too high.
I did not do a too hard ride 76 km, 1083 elevation gain, 31,7 km/h avg. speed and have a avg. power of 267 W and NP 321 (Strava says 303 NP). Can this be true? I have attached the file and profile, I would appreciate if you can have a look (was a windy day yesterday). Thanks.

And then one last thing: I hink there is a issue in the current ISAAC software. When I set up the PP Profile via the configure newton option I chose once handlebar mount for one bike and combo mount for the other bike. In both cases the profile was created with wind scaling 1.0 causing way too low values for flats and descents. I would have expected that the profile would have been set up with 1.7 and 1.4.

Many thanks
Chris

[brianj25us]

And then one last thing: I hink there is a issue in the current ISAAC software. When I set up the PP Profile via the configure newton option I chose once handlebar mount for one bike and combo mount for the other bike. In both cases the profile was created with wind scaling one causing way too low values for flats and descents. I would have expected that the profile would have been set up with 1.7 and 1.4.

Agreed. After a couple of long rides, I noticed the dropout of power on descents, so I started poking around some and discovered the Wind Scaling at 1.00. It was at this value for all my profiles which were generated from the Newton setup. I had remembered reading (DCR???) that 1.4 was the default for handlebar mount, so I used it. It made a significant impact and I see numbers more in line with expectations.

Otherwise, the output looks pretty solid so far without other tweaks. Device pairing was no issue with my old legacy Edge 705 and my fenix 3 wearable. One of my ridemates have Vector pedals and we are within a few percent, so my confidence is high that we're both accurate, or we're both misled equally

Been using raw data from PP and Garmin smoothing. Going to try PP dynamic smoothing with Garmin off and compare once the Colorado blizzard departs!

[Velocomp]

Since the value for the wind scaling seems to influence the overall power on flats and descents most I have still the question what is the best value to use.
@John: You mentioned that 1.7 is best for Garmin combo mount and 1.4 for the mount you ship with the PP (handlebar mount).

Why do those values so much differ? 1.4 to 1.7 is quite a difference as I noticed.
I would assume that the PP mounted in front of everything (Combo Mount) would cause that more air is coming into the PP mouth? Why then the wind scaling value is higher? Or am I wrong?

After you adviced me to switch to 1.7 for my setup with combo mount I changed the value accordingly (before 1.6). Now the values seem to be a bit too high.
I did not do a too hard ride 76 km, 1083 elevation gain, 31,7 km/h avg. speed and have a avg. power of 267 W and NP 321 (Strava says 303 NP). Can this be true? I have attached the file and profile, I would appreciate if you can have a look (was a windy day yesterday). Thanks.

And then one last thing: I hink there is a issue in the current ISAAC software. When I set up the PP Profile via the configure newton option I chose once handlebar mount for one bike and combo mount for the other bike. In both cases the profile was created with wind scaling 1.0 causing way too low values for flats and descents. I would have expected that the profile would have been set up with 1.7 and 1.4.

Many thanks
Chris

Where the PP is positioned on the bike determines the best wind scaling. We use factory values of 1.4 for handlebar and 1.7 for Combo mount, but these values can be fine-tuned by the user for even better performance.

I agree your value of 1.7 is a bit high; I would set it back to 1.6.

Yes, there is a bug in Isaac that sets wind scaling to 1.0. We will need to fix this...

[speedracer]

I did the out-and-back ride today - 6 minutes out and then back (a bit slower due to elevation gain)

The outcome is as follows:


Ride file is attached. Even I thought already 1.7 wind scaling is a bit too much (therefore I used 1.65) ISAAC wants me even to increase wind scaling t 1.75. Rest looks good.

@John: Do you have an explanation? Shall I use this value? Would it be better to do the out-and-back ride with less elevation gain on flat?

[Velocomp]

If you have your PP on a combo mount then the measured value of 1.75 is perfect. I would use it.

[speedracer]

Additional feedback from my side as I did the Out-and-Back ride also with the other bike where I had always the impression that the values are a bit high. On this bike I have also a Combo Mount - also the same K-EDGE.
The results are interesting and fit to the obsevations I had.



ISAAC wants me to change tilt and decrease wind scaling value to 1.586. Ride file is attached.

So from what I learned so far, an out-and back ride is a mandatory part of the calibration to have good power values. Even using same mount on different bikes the required wind scaling can differ a lot. In my case from bike to bike: 1.586 vs. 1.753

The Factory default should only be the starting point.


Btw, I used exactly the same route for both out-and back rides:

[speedracer]

...and last but not least the last (3rd) winter and night ride bike. Wind Scaling factor was adjusted (1.65) too high which could be easily seen from the power values. The out-and-back ride also has shown this directly.
Here the PP is mounted next to the lamp head on a seperate K-EDGE mount:







Again: I can only recommend to everybody to do such an out-and-back ride. Otherwise the wind scaling value is just a best guess. John, maybe it is also worth to mention in the calibration manual which is applied to each PP delivery box.

[Velocomp]

Your measured value of 1.326 is pretty close to the factory setting of 1.4. In other words, the "out of the box" experience would be just about exactly right...

[speedracer]

Well the mount is quite different from the one you ship with the PP. Therefore I was not sure which value to take. But thanks to this out-and-back possibility it is easy to find out what to use in the end.

However, as you can see from the combo experience above the value differ on same mount quite significantly: 1.586 vs. 1.753
Therefore out of the box is close but does not always fit precisely

[Velocomp]

I don't from where the value 1.753 came. That is not a factory default value.

It is FANTASTIC that PowerPod users are taking advantage of Isaac to dial-in the PP, and also to learn more about some of our advanced features.

My only point is that, if you just want to ride your bike, PP will get you consistent and quite accurate results, right out of the box.

[speedracer]

John, I don't want to argue that this is not the case. Don't get me wrong. But I love to play with the toys and get most out of it

My experience with the combo mount on two different bikes shows that there is still possibility to improve accruacy of the power values if you use the out-and-back option:

--> The 1.753 came as result from ISAAC from the out-and-back on my Specialized Tarmac with Combo Mount.

--> The 1.586 came as result from ISAAC from the out-and-back ride on my Cannondale CAAD10 - also with Combo Mount. This was the bike where you also had the impression that factory default of 1.7 was a bit high and you recommended to go back to 1.6. So also the out-and-back value seem be right and confirms our both impressions.

What makes me wonder is the difference for the same mount of ~0.17 with exactly same angle (100% horizontally). So all in all these out-and-back rides are a great thing to either find out the correct value if you are not using a standard mount or to see whether the default values really fit.

[Velocomp]

I absolutely agree that you can dial-in the accuracy of your PowerPod with an out-and-back ride. And it does not surprise me that the same mount will produce a slightly different result on two different bikes.

What is going on is that you and your bike together present a kind of "wall" to the air that is impinging on you. That wall creates zones of different pressure, which change depending where they are measured on the bike. You might not think it the case, but it is a fact that the air pressure zone directly beneath your handlebars is somewhat different from that in front of your handlebars. In fact, there is a slight concentration of pressure beneath the handlebars.

This is why PowerPod has different factory wind scaling factors, depending on where it is located on the bike.

The factory default numbers are based on testing we did prior to production. However, each bike is going to be slightly different, so if users want to get that last bit of performance out of their setups, the out and back ride will deliver it.

[speedracer]

Thanks John for this information. Indeed this helps understanding what's going on.
I really appreciate that you share this kind of information here. I'm more and more happy with having bought the PP even I was a bit skeptical in the beginning.

[questioner]

Hi John,

I used the PP with the original handlebar mount over the winter at my Cyclocross and everything looked fine.
I changed to the Roadbike with a second mount and did an out-and-back-ride. Wind scaling nearly 1,4 (04_04) looked perfekt.
I did some rides in windy conditions but the wattage was much to high. Now I changed the wind scaling to 1,2 (04_28). It seems better, but still a bit to high. So I reduced the factor to 1,1 (04_29) and it seems o.k. but I´m not really sure if these settigs are right.
PP oddly shows sometimes at a slight uphill with tailwind more Power than at a slight downhill with headwind. My legs say the contrary...

Maybe you can throw a glance on the ride-files. Would be great!
Thank you in advance!

PS: Here the files with wind scaling 1,4. I never took the PP away from the mount. Every ride starts and ends at the same place.

[questioner]

And here the files with wind scaling 1,2 and 1,1

[Velocomp]

I agree that on your 4/29 ride the 1.1 factor does look good.

However, you are doing really long rides, and the assumption used in the wind calculations is that the wind does not change during the ride. For a 100KM ride this is a really risky assumption, and it may be that wind conditions are changing in a way that is causing apparent differences.

I would do some short out and back rides. Please post them.

[speedracer]

As add. info: John somewhere recommended a out-and-back ride of 5 minutes each direction.

[nicholp1]

John
I was trying to tune the calibration of my profiles in order to get the best possible setup by doing an out Could I ask you to take a look at the enclosed ride file more so the iBike_04_29_2016_1842_7_km_HiDef.ibr one where I did an out and back. After the ride I used the check calibration feature as I had done with my other profiles and it suggested a windscalling value of 2. I thought the value was high but thought I’d go with it as it might be a result of the mount which I made that sits under a set of controlTec clip on bars http://www.controltechbikes.com/TTbars.php

I’ve also enclosed a picture of the mount I fabricated on the controlTec bars.

2015-12-22 20.26.04.jpg (65.77 KiB) Viewed 19127 times

I applied the profile and ran with that on a longer ride and clearly it was off because I was getting what I considered to be overestimated readings and some long zero drops.

Am I doing something wrong, should I re run the out and back test. I’d love to get a good value set as the mounting position is somewhere in-between standard bars mount and an out front mount. The factory value of 1.4 that I was previously using was giving me what I considered to be plausible numbers but with some zero watts where I was certain applying force downhill.

Many thanks in advance

Pete

[Velocomp]

I agree, the wind scaling factor of 2.0 is way too high.

I would do a new cal ride.

[nicholp1]

Hi John

I got home form work and ran another calibration run over the same distance and route as the previous run ( it was a little less windy today) and then got home and ran the check calibration feature again in Issac. This time it was suggesting Wind Scaling 2.088 -> 2.022.

I was very careful to keep seated and to remain in the same position for the entire ride.

Check Calibration.JPG (63.89 KiB) Viewed 19105 times

I've also enclosed the ride file for your perusal. Let me know me know what you think

Best Regards

[Velocomp]

The wind scaling is consistent with your earlier ride so I would go with it.

However, I noticed that you are getting a few speed sensor dropouts from your combined speed/cadence sensor. If you're using a GSC-10 you might want to check its operation carefully, and think about getting the new Garmin magnet-less speed and cadence sensor, and positioning the speed sensor on the front hub.

[nicholp1]

Thanks John

On my other bikes I have the new Garmin magnet-less cadence sensors and speed ( mounted on the front hub) sensor. For this bike I still have the GSC-10 but thinking about I don't remember changing the battery, ever! I'll put in a new battery and see if that clears the drops, if not I have to invest in more Garmin sensors.

P.S. i'm loving the forum. I guess we could all log our queries via customer support but this gives other people a opportunity to find information and you guys are so reactive and open.

Best Regards

Peter

[speedracer]

P.S. i'm loving the forum. I guess we could all log our queries via customer support but this gives other people a opportunity to find information and you guys are so reactive and open.

Fully agree! I love this 1st hand support and it helped me a lot.

[Velocomp]

Thanks to all for your kind comments!

We learn from the forum as well: the questions that are on your mind and the things we need to do to make better products and user experience.

Keep those questions coming!!

[Bugsbunny]

I'm using ISAAC for MAC - not Windows. Does the "CHECK CALIBRATION FOR OUT AND BIKE RIDE" exist? I can't find it.

[Velocomp]

Open your out and back ride file and then use the command below.

[Wasabibutler]

Hi there guys

Thanks for all the valuable info.

My default profile has a wind scaling of 1.500. This is after calibration. I have not changed anything. I use the handlebar mount.

I will leave it at that for the moment, but going to do an out and back ride to check. Question is, what distance is good for this ride. Obviously a 100km would be bad, due to changing winds etc.

I have a short course at work, roughly 4,5km out which will give me 9km total, would this be enough or would a little longer ride, say 25-30km be better?

Thanks for the support

[Velocomp]

Your short ride of 4-5 km will be perfect.

The idea is to ride long enough to get some decent data, but not so long that wind conditions might change.

[Guido_K]

My PP is mounted between my between my aerobars. The wind port is about 3 cm below the bars.

An out and back ride gave a very high (3.274) wind scaling factor. I repeated the same out and back ride 2 more times and the wind scaling factor is consistently very high.

I could imagine a high wind scaling factor may amplify noise. Is there any problem beyond that?

Thank you!

[Velocomp]

Your rides look fine and your PP is properly calibrated.

Wind scaling is dependent on the position of the PP on the bike. In places where air pressure is higher the wind scaling factor is lower; the converse is true also.

It is OK if the factor is around 3; this won't amplify "noise".