Yeah and no, most dynos are still subject to outside temp and humidity changes. Then add in heat soak, and the fact that a car on a dyno doesn't have air forced into the bay same as a car does that is on the road. (and no putting a fan infront of the car is not the same) On top off all that, you have the dyno queens that do things like remove belts and what not w/o telling anyone they did that.