Questions about a dyno
 

Ok, so I see that that without a load you cant really produce/see your real time boost numbers. Without the resistance provided by parts and the road, you use a lot less gas and make less exhaust I guess. So we check adjustments on the road or a dyno.This makes sense to me. So the question is: how do they decide, on the dyno, the resistance to use? or is it static? I assume the wheel the car sits on and spins gives resistance and forces the car to work harder. But does it account for the 2k pound car differently than the 4k? are the numbers people get from a dyno sort of ballpark? Does the test portion take place at a point weight isn't a factor? Or am I overthinking it? I guess its obvious at this point I am a complete layman. I appreciate any insight you gurus can impart!

There are few different dynos, you have the type you are talking about where the wheels of the car spin the roller in the floor to produce horse power. You also have a dyno where you remove the wheels and attach the wheel studs to the dyno, i believe that is used to get brake horse power. You also have an engine dyno, where you hook the engine up directly and get your hp numbers that way. If I'm not mistaken, they do use a "load" resistance when test on the dyno, but I do not know the exact science behind it.

most dynos reproduce the load a car would have on flat level ground, other dynos can load the car as if going up a steep hill for maximum load.

There are different types of dynos out there, but the basic concept is the same. They have rollers etc for your car to
spin with resistance. The more horsepower and torque your car generates the better it can accelerate against the resistance. The weight of your car has no bearing on how much HP you have.

Your power to weight ratio will determine how fast you can accelerate.