Spend an hour at different settings / speeds, and graph all the things. That should give you a decently calibrated power curve that you can either plot your efforts against yourself, or you can find a reasonable proxy for on trainerroad / elsewhere.
@NotThamesWater started
London Fixed Gear and Single-Speed is a community of fixed gear and single-speed cyclists.
Spend an hour at different settings / speeds, and graph all the things. That should give you a decently calibrated power curve that you can either plot your efforts against yourself, or you can find a reasonable proxy for on trainerroad / elsewhere.