~20 watts drift between Vector 3 and Tacx NEO

Did You make zero offset on your V3 before every test/ride? Crank length is manually entered? Did You torque the pedals enough? (~40Nm). And where did You run these tests? Tacx Training app or in Zwift? Go to the Tacx Utility app on your mobile, and do a reset on on your Neo: https://tacxfaqx.com/knowledge-base/resistance-factory-reset/?fbclid=IwAR2U7vX6BMeo8szikZyR3PS7uaVS5zQHVBYYojMtXPn3qrPREK9asQK6e9s

Meanwhile i found your post in FB Neo group also. Next step could be to test the V3's accuracy: https://support.garmin.com/en-US/?faq=AVZeQisZvi3oBYZUUZdPV6  but use 20kg weight minimum. If the pedals will be accurate in this test, and You did all what i wrote You before, and the difference is still there, send these tests to Tacx directly with Your Neo's SN, and they will recalibrate or change your Neo within days/weeks (depends on your location)

yep zero offset before each ride on the V3, Crank length is correct in the connect app. Didn't torque the pedals. Test was run using the Tacx app and also did the NEO reset before running the test

What makes you think the NEO is faulty and not the Vector 3 pedals?

This is why i suggested to do the advanced torque test (static weight calibration) on V3, You cant check the Neo's calibration at home, but You can check the V3's with that method. And if the V3s have accurate slope calibration, the crank lenght is set good, zero offset calibration good, and the pedals are torqued well (~40nm) on cranks, and still V3s so below then there is big chance that Your Neo's calibration is faulty. Or If You have any friend with other power meter (Power2Max, Quarq, SRM, Infocrank, and no others! ), call him/her to do a test on your Neo, and You will have more info about it. Is it clear?

I have a friend with a stages PM so will bring that into the test. I'm not comfortable with performing the advanced torque test. If the NEO and Stages are similar then ill speak to garmin support for a replacement

Forget the Stages, that is a single sided PM (mostly, there is already dual Stages but that is one of the worst), You dont get reliable data from any single sided power meter, this is why i wrote those power meters what are reliable and forget the rest (and Stages = rest) . You can try the left side Stages one way: you pedal only with your left leg (it is eliminating the leg imbalance), set the Neo at half of the power values than before and record it , so ~40, 60, 80, 100, 120, 150w maximum (depends on your FTP), and the most important thing is your cadence must be constant, within +-1 rpm,  if You cant do that, that is no good for test. And You must pedal  in full circle, smoothly without any sudden pull or push.

ah yes forget stages is single sided!

If you did not tighten the pedal spindles into the cranks (beyond threading them in and giving a little tug with a wrench) then most likely this is part of the problem. The spindle torque recommendation is 25 to 30 foot-pounds (34-40 N-m) but you need at least 15 to 20 foot-pounds to get consistent output. This does not require a torque wrench, but it is a pretty solid pull with a pedal wrench. 

Hi, I have just seen this post from you and I see that this happened a year ago. I am experiencing the same as you, i.e. my Vector 3S pedals show approximately 20 watts lower than my NEO1. I was wondering if you managed to solve your wattage drift, or get an explanation to this? In the best of worlds there should not be a big difference between the NEO and Vector.

I have only seen your post reporting the Vector to show lower watts than the NEO. 

I would appreciate if you could post me any answers to your problem offline to [email protected]. It seems I have the same problem. Is it the Vector or the Neo. It should be mentioned that I have not checked that I have attached the pedals with the correct strenght so to say (40 nm). 

Kind regards

/John