[DanielDudley]

In a no load system, there won't be a whole lot of loss, and there won't be a lot of increase of loss. With a dyno or a car on the road, when you use that power, you are loading the system.

There is a reason why you can only run so much power through a 915 gearbox, and that is because the load keeps increasing with the power. If you are just using the engine to spin the gears in the air, not much load, and an engine with twice as much power won't do much to the losses, but you won't need to use all that power to spin the gears to red line either, so it isn't really a test of the system.