Doing some reading and discover that some power meters may report innacurate reading if you are using an oval chainring which i am. Does the v3 account for this? I read somewhere that the V1 does not but then again i know the v3 have better accuracy
That article describes the situation pretty well. All Vector power meters (1/2/3) currently assume an average crank velocity for the power calculation, so a varying actual crank velocity will over-inflate the torque when the velocity is lower than average, and under-inflate the torque from the part of the crank cycle where the velocity is higher.
The actual power error is given by the square of the velocity variation. Ten percent (as in the example in the article) velocity variation will give one percent power error. The alignment of the crank rings will typically cause the error to over-report the power. Since this relationship is fixed for a given crank setup, you could compensate by adjusting either the crank length or the scale factor downward by an appropriate amount.
Darn that is a bummer, I am regretting not getting the assiomas. I wonder though if the oval rings (I have the absolute black 48/32) have any effect on the Power readings from my Hammer trainer which i assume the PM is in the hubs. Last comparison I made with the V3 and Hammer power has 1% variation so it was really close.
IMHO don't worry about it. Years ago I bought a bike from a pro team and it had Ovals (rather extreme too). I would swap that bike with my road bike often times using my Kickr trainer and do the exact same erg mode power workouts using my Vector1 and later Vector2. I never noticed any difference in power. Maybe that 1% was so small I couldn't notice it.
The bike dynamics however was significantly different from round rings vs oval. My start and end power on the ovals was much more consistent and probably related to where the power phase starts on the oval. That alone was why I bought some absolute black ovals for my other road bike, but the through hole disc brakes was not compatible on my old Kickr so I was never able to try that bike on the trainer.
Bike dynamics certainly is noticeable even my Peak Power Phase shifted a pretty good bit according to Garmin's Cycling Dynamics. Probably a placebo effect but I am liking the oval rings since I've used it. Just bummed the Vector 3 is not automatically accounting for this option.
I did an ERG ride on a target power of 125w and 100w on the trainer with Zwift reading and controlling power from the trainer. The Cycleops Hammer trainer (which has a Powertap hub PM i assume) reported an average of 124w VS the V3 which has an average power of 121w for the segment, a 2% discrepancy. Also on a target 100w the Hammer reported 100w average and the V3 95w average a 4-5% discrepancy.
I was expecting for the V3 to report higher wattage because of the Oval chainring but seems to be the opposite. Given the Cycleops Hammer has a +/-2% accuracy. Will try comparing higher wattage next time but it seems the higher the wattage the less discrepancy happens.