New to power meters - surprised by power readout

Former Member over 6 years ago

Hello,

Apologies if this has already been addressed here - I trawled this forum for a while but didn't quite get the answer(s) I had hoped for, so I'll try asking anyway.

??????I am unsure of the power data that I am receiving from my Vector 3S pedals. However, the only thing that I have to compare it to is the Virtual Power calculation from the rear wheel speed and my trainer's power curve.

For reference, I have a Tacx Booster magnetic brake trainer on level 6 together with Garmin Speed and Cadence sensors. My calculated FTP is 179W. When I first received my Vector 3S, the batteries were dead and I was forced to change them immediately to get the pedals to work at all (this issue I raised with my supplier). After installing new batteries I upgraded the pedal firmware to v3.50 immediately from Garmin Connect on my phone.

I have the correct crank length entered in the settings, auto-zero enabled and have conducted a calibration before riding (successfully, with a zero result). When I ride, I use my Forerunner 920XT as the "head unit" and keep the virtual power calculation in the training app I use to compare the numbers. I have heard and read that one usually experiences a "loss" in power when moving from Virtual to Actual power.

However, when I ride I see that the Vector 3S consistently reports a power output 60-70W greater than that of the Virtual Power, meaning that my Vector 3S FTP is near 250W. As a non-racing cyclist, I find this a little surprising and borderline unbelievable. I do not have the tools or opportunity to conduct a torque test to verify the pedals. Is there something else I can do to confirm correct operation of the pedals?

0 Former Member over 6 years ago

i want to ask you if it is possible that after some time of using to be necessary scale factor correction .i am very adapted to training indoor and outdoor and i also have used a lot of powermeters from Quard Dzero to Power2max and others.also first month the Vector 3 and quarq Dzero were in 1 watt accordance ,that s very very good and 3-4 under p2max ngeco which is known to be a little on the low side.anyway after 1000 km and switching them from bike to bike i have had strugling to holf a power even 20 watts lower that i can aven outside.So my training ia very structured in this time year and 12-20 watts are a very very much for me.so i conducted a static torque test with a measure system of 10.42 kg (weighted on 2 digital scales)and 170 mm cranks.my results were like 16.58 for the left and 16.72 for right pedal.so i put a scale factor of 1.35 or so even little that the result to dont make them read higher.bo they seem to read very good but the question remains:can this scale factor be necesary after some time of using and if yes ,why?

0 Former Member over 6 years ago

It is fine to do the zero calibration before you start riding - as long as the system is at thermal equilibrium. It will track through temperature changes afterward.
On the 920, after you do a zero calibration, apply a load to the pedal. You will see the torque value on the display change to reflect the applied load.

.i am very adapted to training indoor and outdoor and i also have used a lot of powermeters from Quard Dzero Power2max and others.also first month the Vector 3 and quarq Dzero were in 1 watt accordance ,that s very very good and 3-4 over p2max ngeco which is known to be a little on the low side.anyway after 1000 km and switching them from bike to bike i have had strugling to hold a power even 20 watts lower that i can ,even outside.So my training is very structured in this time of year and 12-20 watts are a very very much for me.so i conducted a static torque test with a measure system of 10.42 kg (weighted on 2 digital scales)and 170 mm cranks.my results were like 16.58 for the left and 16.72 for right pedal.so i put a scale factor of 1.35 or so even little that the result to dont make them read higher.now they seem to read very good but the question remains:can this scale factor be necesary after some time of using and if yes ,why?

0 Former Member over 6 years ago

It is fine to do the zero calibration before you start riding - as long as the system is at thermal equilibrium. It will track through temperature changes afterward.
On the 920, after you do a zero calibration, apply a load to the pedal. You will see the torque value on the display change to reflect the applied load.
The picture shows the 920 display while pushing on the pedal.

Right - I am sorry but you're really going to have to walk me through this. If I unclip and perform a zero calibration, I get a successful 0 offset display but I cannot get a torque display, no matter how or when I push the pedal. How do you get that display?

0 t_smit over 6 years ago

What firmware version is your watch on?

0 t_smit over 6 years ago

can this scale factor be necesary after some time of using and if yes ,why?

The scale factor adjustment was provided for users to fine tune their pedals' response for their specific installations, and to allow purposely tweaking the output to match other power meters. The response of the pedals should not change over a period of 1000 km. When you move the pedals from bike to bike you will have to ride them a little with some hard efforts, and then re-set the zero calibration.

Note that when you put in a calibration factor that is different from 1.000, it does NOT change the value reported by the torque display. You always get the uncorrected result. This is to avoid having to know what the current calibration correction is, when you are calculating a new factor.

0 Former Member over 6 years ago

The scale factor adjustment was provided for users to fine tune their pedals' response for their specific installations, and to allow purposely tweaking the output to match other power meters. The response of the pedals should not change over a period of 1000 km. When you move the pedals from bike to bike you will have to ride them a little with some hard efforts, and then re-set the zero calibration.

Note that when you put in a calibration factor that is different from 1.000, it does NOT change the value reported by the torque display. You always get the uncorrected result. This is to avoid having to know what the current calibration correction is, when you are calculating a new factor.

my calibration number on edge 520 is always a torque value -0.16,+0.03 and so on ,not a stable number.
also how much is power inflated at a 1.35 scale for a true value of 200 watts for example?is it like 7 watts?

0 Former Member over 6 years ago

my calibration number on edge 520 is always a torque value -0.16,+0.03 and so on ,not a stable number.
also how much is power inflated at a 1.35 scale for a true value of 200 watts for example?is it like 7 watts?

how do you reset zero calibration?you mean press calibrate againg (manual zero offset)which i done 2-3 times and also during ride when indoor after 10 minutes.

0 Former Member over 6 years ago

What firmware version is your watch on?

v9.80

0 t_smit over 6 years ago

my calibration number on edge 520 is always a torque value -0.16,+0.03 and so on ,not a stable number.

That is normal. It is showing you the torque being measured in real time by the pedals.

also how much is power inflated at a 1.35 scale for a true value of 200 watts for example?is it like 7 watts?

I think you mean 1.035? That would be 3.5 percent, so 7 watts.

0 Former Member over 6 years ago

That is normal. It is showing you the torque being measured in real time by the pedals.

I think you mean 1.035? That would be 3.5 percent, so 7 watts.

that s what i supposed too but today set them again ant 1.00 and at 250 watts (same speed ,gear comb and cadence,tyre pressure and temperature)the difference was only 2-3 watts compared to yesterday.also at other power like 225 and 914 cadence the difference was same.