Power variance between VirtualPower and 4iiii power meter

'lo there

I’m using VirtualPower on a dumb trainer for my TR sessions and all is working just fine, but there are huge variances when I ride outside with a 4iiii power meter ?

There is no way I could sustain 300+ watts on a TR session for say 5 mins as I’m a fat knacker but when riding a hill outside the 4iiii power reading is showing 300+watts effort for a hill climb? I’ve matched my 4iiii FTP with my TR FTP so is it just down to the fact that my trainer is dumb and can’t replicate a hill climb ?

you’re comparing an estimate to a real device.
you need to test with the real device.

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Virtual power is an estimate and can be pretty wrong in all honesty. You 4iiii power meter will report your actual power (provided you calibrate it).

Why don’t you put the bike with the power meter onto the trainer, and train with real power?

If you’d rather keep the two separate, you’ll have to do a new ftp test outside, with the 4iiii bike - a 20m test probably.

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Yeah, think I’m comparing apples to oranges to a degree, I’ll do a 20 min FTP test later and see how it compares - If I’m honest the power meter has only served to complicate matters, beforehand I’d climb a hill based on speed and %gradient from my Garmin and that seemed to pace me well so I didn’t burn out. Powermeter seemed to be the next step in progress but so far I’m just not getting it

Also 300W on a hill doesn’t seem that wrong, if you’re on the heavy side. I assume it’s not an hour long climb?

The first step is to recognize that the two values (VP / RP) are “different”. They cannot and should not be compared on a like for like basis.

Beyond that, you suffer the same dilemma as anyone else who adds a second power measuring device…

“A man with a watch knows what time it is. A man with two watches is never sure.”
Swap watch with power device and there you have it.

Best case since you own a power meter is to use it for training inside and outside. That’s not always practical for everyone, so recognizing the difference between the devices is important. Learning the delta between them is necessary if you plan to use power for setting efforts inside and outside.

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