They're both incorrect, I think. Acceleration rate would be the rate of change of the rate of change of speed, or what is known as 'jerk' in engineering. I guess that would be the time that it takes to go from 0 to the '0-60 in 1.8s' acceleration? The correct term is simply 'acceleration' on its own.
alls i'm saying is that if anyone wrote "acceleration speed" on reports in high school physics class they'd get points off. acceleration is a kind of rate.
