Tacx Flow Smart watt accuracy - Keo Power pedals

Anything about Power (watts)

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NorwayBike
Posts: 2
Joined: Sat Oct 29, 2016 5:32 pm

Tacx Flow Smart watt accuracy - Keo Power pedals

Post by NorwayBike » Sat Oct 29, 2016 11:26 pm

Hello
I bought a Tacx Flow Smart. Got a bit frustrated not knowing if the wattage was correct, so I bought some new Keo Power pedals. Got tired of trying to find the perfect way to calibrate the Flow, searching the internet, and the lack of help from Tacx (they should present the watt accuracy test by themself). I'm also a watt-geek and engineer, so watt, Nm, torque, and rpm is not a unknown issue for me.

So, here is my result.
Conti 4000S - 23mm tire. 100-110psi. From touching the wheel with the roller, I turn the screw +2.0 turn, ride at 150-200w for 10-15mins. Then i calibrate. After that I turn the screw another +0.25 to 0.5 harder. (Don`t calibrate afterward) Then the wattage is +/- 0 to 5 watt, from 150 to 350watt!! Not bad for a cheap trainer. :)
At 100watt I need to go up to around 120 Flow watt before it's real 100w. From 100 to 150watt something happens, and the Flow get's more and more correct, until 150w when it's matching the keo power up to 350w ( haven't testet higher).

But I find the difference get at bit higher (+0 to 10w) if I ride long time on high wattage. I guess because the tire gets heated up. If I stop for a minute, the watt accuracy is back again to 0-5watt. I normally train between 150-300w, and got perfect result. Have not struggeled to get it more correct below 150w because I use the trainer only for resistance for my pedals, and never train below 125w.

Be aware of lower tire pressure. Lower pressure from the calibrated pressure gives huge errors.

Another thing. The keo power is very accurate, BUT, you need to install correctly and calibrate correctly. I have also testet the pedals way in and way out. Just a millimeter wrong installation, you get wrong wattage. The same with too tight og loose mounting. Use a torque wrench, and be aware how the pedals touches the crank arms.

Hopefully this can help you, Tacx Flow Smart owner :D :D

If you have a "perfect" calibration method (and conti 4000s), please tell me, and I can test it (for you and other Flow Smart owners)

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ms6073
Posts: 1824
Joined: Sat Oct 07, 2006 9:06 pm
Location: USA, Houston, TX

Re: Tacx Flow Smart watt accuracy - Keo Power pedals

Post by ms6073 » Sun Oct 30, 2016 12:57 pm

if you are using the Tacx Trainer Software (or Tacx App), you can connect your Keo power pedals to the application, and TTS will display the power from the pedals instead of the Flow. While this won't resolve the discrepency, you can record the training on your head unit and use that for tracking power metrics instead of TTS.
TTS 4.19.1 | T2800 NEO Smart [formerly Bushido & Fortius]
MSI GS70 Laptop | Windows 10 x64
Intel Core i7-4710HQ 2.40 GHz | 16 Gb DDR3 1600 MHz
GeForce GTX 870M | 256 GB SSD x 2 RAID 0 + 1 TB HDD
Samsung 32" LED TV

NorwayBike
Posts: 2
Joined: Sat Oct 29, 2016 5:32 pm

Re: Tacx Flow Smart watt accuracy - Keo Power pedals

Post by NorwayBike » Mon Oct 31, 2016 7:25 pm

Have tried it. Tacx software (TTS) does not follow the BLE protocol correctly I think, and can not connect to two pedals at once, or receive the pedalpower x2 from one pedal. Which means only half the power shows on TTS. Fulgaz and Kinomap does recieve power from one pedal correctly, and shows correct wattage.

Forgot to mention one thing. The above test is with zero slope. Above 3% the wattage gets incorrect, but I have not tested this much, because I mostly use the Flow as a fluid trainer for my Keo power pedals (powercord unconnected)

Would be nice if Tacx could tell exactly how they have tested/calibrated the Flow trainer, tire pressure, screw turns, heat up before calibrating, and the accuracy they got when testing/graph.

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ms6073
Posts: 1824
Joined: Sat Oct 07, 2006 9:06 pm
Location: USA, Houston, TX

Re: Tacx Flow Smart watt accuracy - Keo Power pedals

Post by ms6073 » Mon Oct 31, 2016 9:52 pm

NorwayBike wrote:Have tried it. Tacx software (TTS) does not follow the BLE protocol correctly I think
That might be part of the issue as Tacx trainer Software on a PC is not Bluetooth capable, and only supports ANT+ device connections. I may be mistaken, but I think even the Tacx App for tablets supports only Bluetooth for connecting to a compatible Smart trainer, and uses ANT+ for connecting to other devices such as external speed, cadence, or powermeters.
TTS 4.19.1 | T2800 NEO Smart [formerly Bushido & Fortius]
MSI GS70 Laptop | Windows 10 x64
Intel Core i7-4710HQ 2.40 GHz | 16 Gb DDR3 1600 MHz
GeForce GTX 870M | 256 GB SSD x 2 RAID 0 + 1 TB HDD
Samsung 32" LED TV

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