Watt dissapear in Isaac

[NorBike]

I try to hold constant 350 watt for 60 sec. (manage to stay between 330-365w). iBike Newton shows 342w avg.
When I import the ride file to Isaac I get 313watt avg (?!?).

I ride for a longer ride trying to hold 250w avg. iBike Newton shows 246w avg. Isaac 213watt (?!?)

Hmmm..maybe this have something to do with the Wind Scaling bug( http://www.ibikeforum.com/viewtopic.php?f=55&t=2534 ), so I look in the "advanced stats" in after a climb at 18km/h.
Isacc shows 394.4w in avg, but seperatly 344w + 21w + 54.3w = 419.3w avg.(!?)
(And where is the cm1,02 factor?)

newton.JPG (6.7 KiB) Viewed 6781 times

Has Isaac Newton lost his mind?
.

[Velocomp]

Please post the ride file

[NorBike]

My examples was from different ride files.
Ride files does not show what I see in the iBike Newton display, so not sure if any point in posting ride files to show the watt difference between Newton vs. Isaac.
Also, watt loss in "Advanced stats" seemes to happen in all my ride files in Isaac. Just open any files, and calculate the avg. watt from aero, rolling, gravity vs. avg. power in advanced stats.

One other issue I have found is that when I ride at 20-25km/h and I see a avg. wind around 0-1km/h in the Ibike display (wind free day/area), when import the ride file Isaac shows avg. win around 5-6km/h. I have calibrated my Newton with a SRM now, and manually adjusted the wind scaling and get very similair wattage readings bettween Newton and SRM. If i use the wind scaling Isaac recommends I get wind around 0 km/h in Isaac, but the Newton get way off with that wind scaling. I hope there will be a solution for the wind scaling difference i Ibike and Newton soon, so when I import my ride files I can trust Isaac.

[Velocomp]

My examples was from different ride files.
Ride files does not show what I see in the iBike Newton display, so not sure if any point in posting ride files to show the watt difference between Newton vs. Isaac.

We can't help if we don't have data.

[Russ]

Hey NorBike,

Give Velocomp a crack at the problem with your files. Remember, they have extra data recorded that we can't access with Izaac. They may be able to sleuth out something that you and I can't anticipate!

Just my 2 cents worth
Russ

[Zoltan]

I try to hold constant 350 watt for 60 sec. (manage to stay between 330-365w). iBike Newton shows 342w avg.
When I import the ride file to Isaac I get 313watt avg (?!?).

I ride for a longer ride trying to hold 250w avg. iBike Newton shows 246w avg. Isaac 213watt (?!?)

Hmmm..maybe this have something to do with the Wind Scaling bug( http://www.ibikeforum.com/viewtopic.php?f=55&t=2534 ), so I look in the "advanced stats" in after a climb at 18km/h.
Isacc shows 394.4w in avg, but seperatly 344w + 21w + 54.3w = 419.3w avg.(!?)
(And where is the cm1,02 factor?)

newton.JPG

Has Isaac Newton lost his mind?
.

I dont want to hijack the thread, and I am not fully familiar with Isaac, but if you make a short ride with different start speed and end speed meaning a start and/or trip reset during the ride, you have more power factor, namely that from acceleration. In your case the speed seems to be fully in a narrow range, so acceleration is not the root of the problem.

But what is more than suspicious is that the min Paero must not be zero if the min speed was 17.7km/h. Just a note from me, no more

[NorBike]

1. Isaac watt calculations:
179.1w + 42.9w + 17.5w = 239.5w. Isaac calculate = 200w.

1.jpg (213.45 KiB) Viewed 6534 times

2. When caclulating these forces separately, they are correct and should be 240w. (without the cm 1.02 factor):

2.jpg (79.08 KiB) Viewed 6536 times

3. Around 240w(+/-) is also what I see in my Newton display.

- Don't understand why Isaac calulate the avg power = 200w ?
- Where's the cm x1.02 factor?

NorBike

[KenS]

I've done some similar experimenting with Isaac and found that if you subtract the gravity watts then you get close to what Isaac is showing. Which in your case would give you 204W which lo and behold is 1.02 x 200W
Also, whilst your braking is 0% you also need to factor that in if it is non-zero.

[Zoltan]

Having seen the new data I still have the same question. If min of Power is >0 that is there is no coasting, how min of Paero can be zero?? Theoratically there is one explanation, having the same speed of tailwind as the bike speed relative to the ground.

But in the screenshot from Norbike the min wind speed is above zero.