Adjust Trainer Power to Match PM on outside bike

Is there any way of adjusting the power reported by the trainer to match the power from your your outside bike so your metrics are the same inside and out. Ie my trainer reads consistently 9% lower than my power meter on my bike.
1 .I know what Power Match is and that is not what I talking about and
2. It is not feasible for me use my outside bike on my trainer on a consistent basis.

How do you know that your trainer reads 9% lower?
Probably because you set up your outside bike on the trainer and compared power output from both?
Are we talking about a wheel-on trainer?
If so, this will sound disapointing but with another bike on your trainer, it is almost 100% sure that power values will be different. That is because power from a wheel-on trainer is very dependent on the bike/trainer interface. Two different bikes have a different position on the trainer and thus the tension off the trainer roller on the tire is different. The tires are different and probably the tire pressure is different. So you can’t simply port the power from one bike to another on these trainers.
If you can temporarely transfer the power meter to your inside bike, you can make it match quite closely. Check this post:
After doing that, remove your Power Meter and do not recalibrate your trainer!

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Yes I’ve put my outside bike on the trainer for s number of rides and 9 % is the average variance. It’s a wheel off trainer (Elite Zumo) and die to where I live it’s not practical to keep taking the bike in & off it.
There are lots of posts on numerous forums about this issue and it seems to me there is a simple solution. On the the training platform enable a power scaling factor to increase or decrease the reported and recorded power. Xert used to do it but the feature is missing from the latest apps. There are ways round it but it’s inconvenient and time consuming

That simple solution would be confusing because the target sent to the trainer can’t change and the output would be scaled. You will constantly see 2 different Power numbers and the output graph will float above or beneath the target graph…

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This is interesting. It’s like power match without a second power device. Now that I hear it I am surprised no one else has requested this. This does sound easy but somehow it scares me that it might not be. Let me think on this a bit.

It’s difficult to explain but here goes
Say I’ve got the Trainer and my power meter on together and I’m pedalling at 100W as measured by the Trainer. I’m actually putting out 109W (from the power meter and measured concurrently on say a Garmin). If I was then to put the Power Scaling factor to 1.09 and continue pedalling at the same intensity the App which is showing the power from the trainer would show 109W which would now match the 109W shown from the PM on the Garmin because the intensity hasn’t changed. In this case the .fit file from the app would show the initial period at 100W then the 2nd period at 109W.

one problem is that the % variation can change with intensity and sometimes it can be a fixed offset plus a % variation. My take however is that being out by a variable plus or minus 2/3 % is better than being out every time by 9%

I get it but thanks for clarifying.

Yes, I agree makes sense.

It might be a simple solution to use PowerMatch function to correct a “virtual” power meter with a simple scaling factor.
I know that TrainerRoad does (did) powermatch with several functions. One was a permanent offset.
In this case the target sent to the trainer should be scaled to 91% but displayed as 100%.

Forget about the “measuring” from the trainer. There is not one single trainer that measures power. The trainer takes a target Power and puts you on a predefined speed/power curve. Riding at a specific speed creates a resistance determined by that speed.