Turbo Vado 2 4.0 or 5.0 or 6.0?

[Jeremy McCreary]

A new trial, a little longer and with more rider effort to more clearly define Pm saturation values. I just did 40/40 and 40/100.

We clearly have the right guy on the field work. Thanks!

Q: Just to be careful, your cadences on these trials?

.fit file data
View attachment 206039

View attachment 206040

Again, strong confirmation that Pm really is linear in Pr before saturation and almost flat in Pr after. So that part of my simple Pm model holds fairly well. And that makes our reverse-engineering task much easier.

and my comparison plotting the functions together:
View attachment 206041

Excellent! Writing an assist mode as E/M, let
Pe = electrical motor power
Prs = rider power Pr at the saturation point where ramp meets flat
Pes = Pe at Prs
Pex = Pes at M = 100
S = ramp slope.

Took the S values below from the .FIT file linear regressions and visually estimated the Prs and Pes values from your summary graph.

For Ride 1 at 40/40, Prs1 ≈ 285W, Pes1 ≈ 210W, and S1 = 0.7

For Ride 2 at 40/100, Prs2 ≈ 245W, Pes2 = Pex ≈ 380W, and S2 = 1.51.

In principle, we should get S1 ≈ Pes1 / Prs1 = 210 / 285 = 0.74 and S2 ≈ Pes2 / Prs2 = 380 / 245 = 1.55. And in both cases, we get reasonable agreement. So far, so good!

But the empirical Pes values raise an issue. My simple Pm model uses

Pes = Pex (M / 100)

If that were true, we should have Pes1 / Pes2 = M1 / M2 = 40 / 100 = 0.40. But empirically, we get Pes1 / Pes2 = 210 / 380 = 0.55, a significant discrepancy.

So Pes must be more complicated than the simple model assumes. Efficiency variation via cadence could be involved.

Problem is, if you can't predict Pes from just M and Pex, it's gonna be hard to estimate Prs — which is my main goal in this reverse-engineering project.

 

[mschwett]

Could you specify this data, just so we're all on the same page?



Could you show us exactly how you got that curve — presumably the one below?

...

from the "03 - Turbo Vado SL 2" page at https://support.specialized.com/kb/...-Vado-SL-2-Turbo-SL-System#MotorTuneEasePower

essentially we have 13 different values of required rider power for full motor support at 80rpm with varying ease xx/100. you could argue that one should use 295 mechanical watts here when computing the ratio, since the power chart only shows 295 watts at 80rpm. but i used 320.

the curve is just a fourth degree polynomial trendline. the r^2 is very good at .996

 

[mcdenny]

Jeremy, I eliminated all records with cadence < 60. The data at low power, low cadence is very noisy. Most of the records are in the 70s and 80s with relatively few 90s where I’m really pushing.

 

[Jeremy McCreary]

Jeremy, I eliminated all records with cadence < 60. The data at low power, low cadence is very noisy. Most of the records are in the 70s and 80s with relatively few 90s where I’m really pushing.

Excellent!

 

[mcdenny]

I did three more test rides this afternoon. 5 minutes at 100/40, 20/100 and 30 minutes ar 20/20. Unfortunately I could not download any of these 3 .fit files. As soon as I click “download” in the app I get an error message saying ”Sorry, can’t download. Try again later”. It never works later. In my testing over the last days i get this error maybe 1/3 of the time. Anyone have any advice?

I have a display showing Pr, Pm and cadence. 100/40 worked like I thought - really easy to get to Pr sat. IIRC, Pm max was about 170 watts. I’d really like to get at the granular .fit file data though. I was able to get some bursts of Pr in the 400s. At 20/20 Pr sat gave Pm of 70ish. I could not reach Pr sat for 20/100.