Applying the throttle during ramp run

I understand that when carrying out a ramp run we should be in 4th gear and starting the run around 1500 rpm. My question is how the throttle is applied during the course of the ramp run.

Is the throttle pushed down gradually throughout the run as rpm increases gradually all the way up to wide open throttle (redline) or is the throttle pushed down all the way immediately as the run begins and the engine naturally ramps up to wide open throttle (redline)?

There are a couple of variables that come into play here, if it's a hub dyno you have all the engagement and control of the car so can hold full throttle before the dyno begins the run no matter the power of the vehicle.

If it's a small roller dyno and a high-torque car, such as a boosted V8, then you might find traction becomes an issue when loading it up too soon.

Sorry, forgot to mention that I do not have access to a dyno so my question is regarding a ramp run while road testing

Generally you are concerned with wide-open throttle during a ramp run, so you would apply the throttle as quickly as possible given the traction. If there is no traction problem, then you can smoothly (cruise throttle to 100% throttle in about .5 - 1 seconds) go full throttle immediately. Another technique, is to apply brake and throttle at the same time, then just release the brake -- this is exactly what the hub dyno does.

If your ramp run is for a different throttle position (or manifold pressure), then just use that as soon as possible, and try to keep your foot steady.

Great. Thank you all.