I don't know why their dyno sheet would refer to flywheel hp ...unless they just input a driveline loss number into the program and then the computer just calculates what flywheel power and torque would be from the measurements at the rear wheels.
It's very common of dynos in Europe to read flywheel hp. There is a calculation software in the dynos to get the readout. You make the pull and put the car on neutral and let the wheels and drive train to slow down the wheels. The dyno measures how much hp does it take for the wheels to slow down and it adds it to the wheel horse power figure.
Here's a pic that I found:
On top is the wheel horse power figure, and below is the calculated drive train loss. When they add those two together, you get an estimated flywheel horsepower figure. That is an old Bosch dyno, just to give you an idea. On newer dynos, the calculations are made automatically if the dyno operator prefers to give out flywheel figures.
Same thing here but on a newer dyno that calculates it automatically:
Green line is drive train loss and blue line whp.
206whp +
65.9hp = 272 fwhp
Hope this clears things up
