I have an Elite Elastogel fluid (dumb) trainer, and even though I’ve not used Virtual Power with it, I can say with an enormous amount of confidence that Virtual Power on this trainer will be absolutely crap. The power curve of the trainer just isn’t predictable enough.
I use the trainer with TR, but I use a 4iiii PM. As the trainer warms up, it provides less resistance so I need to gear harder or increase cadence to maintain the same power. During a normal TR interval workout, the resistance will drift quite a bit - this makes it very difficult to predict the power needed to spin the trainer at a certain speed, so very difficult to generate a representative power curve for the trainer - which is what Virtual Power is.
Your Suito will be way more accurate than VP on the fluid trainer - trust that FTP.
My advice to anyone using virtual power on a fluid trainer: If you don’t have a power meter, use FTHR rather than FTP, and look at your past workouts to get an idea of what sort of wheel speed you need to hit certain HR zones (this will reduce the impact of heart rate lag on your workouts and enable you to get in the right zone at the beginning of the interval). You’d probably even be better off holding off of TR workouts until you get a PM, and going more old school with your workouts, like the British Cycling ones (if they can still be found for free). This approach worked really really well for me for a couple of years before I moved to power, and even worked for the pros for a couple of decades before power meters got small/cheap enough to use outside the lab.
