I’ve been training with virtual power on my KK Road Machine up to this point. Yesterday I ordered a 4iiii left side power meter. For those who have gone from virtual power to real power how big of a difference did you see in your power output?
Admittedly, this meter will not fit on the bike that I normally have in the trainer. (different crank) My plan is to mount up the bike with the PM to the trainer and not pair the pm to TR, but to my head unit and see what the difference is. My hope is that this will give me an idea what the difference is between the two so that I can use my power meter for training/pacing when I’m outside.
Virtual power varies with setup. I doubt any users experience will help you. Just see where your numbers are and work your way up!
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Should be within 20% - good luck 
There’s a chance it will be spot on! Not a high chance but there’s a chance
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It’s tough to say, but really easy to find out! Here’s hoping the numbers work out in your favor. 
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All depends on how tight did trainer wheel up, what pressure tyres…etc etc. Impossible to say really. When I moved from VP on kinetic road machine to 4iiii the power at low intensity and sweetspot as pretty close, but as power rose the VP got further away from 4iiii (VP reading higher). By v02 levels there was quite a difference. Always found v02 work easy under VP…not anymore!!!
This was my first ride with power meter and virtual power. I thought i would be off but would have been nicer if it wasnt so much. Hope yours is closer/higher see comments for comparison …Log In to TrainerRoad
Cool, thanks for the info. @Leopard using the ramp test is a great idea for doing the comparison. I hadn’t given much thought to how I wanted to do that yet.
I went from VP to a Stages left power meter and the difference was soul destroying
As with the OP the VP and the Stages were on different bikes but i was so deflated i contacted Stages to see if i had a duff product (oh the vanity)
Anyway fast forward 2 years and my “real” power had now increased to that of my VP power when i swapped.
Like others have said set up with VP adds quite a lot of variables so dont be too disheartened if your numbers dont match up 
I have a single-sided 4iii on my set up and use a Tacx Neo. I don’t use VP, but I do like to observe how the two match up during workouts. I find that at lower intensities, the 4iii reads higher (up to maybe 15-20% at very low intensity). The gap then closes as the intensity increases, there’s a convergence and, at threshold and above, the Neo reads a little higher.
Actually, The very first ride I went outdoors and tried to hold VP ‘threshold’ and blew up after 3 minutes 
I wasn’t too bummed with being lower than I thought because it means I’ve probably still got some beginner gains to be had
I went from an elite Chrono fluid wheel on trainer to a tacx flux direct drive and dropped from 305 to 265w. A humbling experience, but at least you now know your numbers are more accurate
30 watts for me at threshold
It’s just a number.
If you work just as hard, and it feels just as hard, and you still get stronger over time, who cares? Your FTP could be 120, or it could be 12,000. It’s a number.
I’m pretty sure you win a race by crossing the finish line first, not by having the highest FTP or w/kg.
SO, enjoy the power meter (they are fun to have!) but don’t lose sight of the real reason to ride the bike and train hard with TrainerRoad.
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In my case, a lot. If you can record the same indoor ride in 2 different apps, and export from them, you can really analyze the difference in DC Rainmaker’s Comparator app. https://analyze.dcrainmaker.com/
I later got a Direto, and there’s a difference between it and my 4iiii too. The good news is that the 4iiii app allows you to adjust its reported power up or down if you want to “correct” it or match another device. I use the Direto’s very stable meter to control and record inside rides, and am reasonably sure that the “corrected” 4iiii outdoors is giving comparable numbers for comparable efforts. As many note, as long as a meter is consistent, it doesn’t matter how absolutely accurate it is – IF that’s all you use. But if you go from one to another, there may be some big surprises.
Man, what’s the w/kg of a man with a 12,000 FTP 
.
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I lost 30 watts on my FTP.
Kurt with VP to left side 4iiii.
I dunno. What is the airspeed velocity of an unladen swallow?
African?
What do you mean? An african or a european swallow?
UPDATE: My 4iiii power meter arrived yesterday! Last night I installed it on my trainer bike and paired it to my head unit. I left my TR workout set up on virtual power and went about my scheduled workout.
After a brief warm-up I did the zero offset procedure and started the workout. Throughout the workout I looked at TR and my head unit several times to compare readings. After the workout I did a little data crunching and was very pleasantly surprised that my virtual power numbers and the power meter were very close. I looked at different output levels and did comparisons as well as avg. and n.p. for the workout as a whole. Avg and n.p. were within 3 watts of each other for the two measurement devices.
I’d say TR has the power curve on Kurt Kinetic’s road machine dialed in! I’m planning to export data to Golden Cheetah and analyze a bit more, but since we’re well inside the margin of error it’s just mostly to kill time…
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