[steve shadows]

We don't just hold the car in steady state the whole time.

We pull it up through sweeps under a given load - this load can be adjusted to simulate the most appropriate amount of drag on the drivetrain ,

We can simulate the way the engine will actually operate and much much more. We can simulate drag racing, full throttle pulls in any gear, and adjust load to match particular conditions that we would like to simulate. This is why rally shops love these things, you can simulate uphill, program corrections for BARO and do WOT pulls in every gear or bring WOT pull up to a certain point and hold for trouble spots in the map as well.

You can't adjust this with an inertia dyno, it's one size fits all - weight - the drum represents a given weight or load on the vehicle that the vehicle has to overcome - it's a measurement of the car overcoming the movement of a given weight- No adjustment can be made and the weight of the vehicle on the roller (the amount of mass or weight of the vehicle moving it) is also left out of the equation- at least the last time I used a dynojet straight roller dyno. It's actually audible - the surge on. When you roll into 4th gear in your turbo powered car when it has full traction with the road does it surge faster through the rpms? The dyno dynamics in WOT mode simulates the exact same conditions as accelerating

Dynojet numbers are often closer to MFG suggest brake/flywheel outputs than they are actual road power numbers