To get the thing absolutely right (I think) . The accepted symbol for angular acceleration is the Greek Alpha.The symbol for angular velocity is the Greek Omega. So you had the symbol right but the wrong definition.
As you say, using an inertia dynamometer, The engine simply accelerates a flywheel of known I ( inertia) value.
Feeding into the software we have instantaneous values of angular displacement (theta) and time.The software calculates instantaneous angular velocity (theta/time) to give instantaneous angular velocity (Omega),It then compares this angular velocity value to that existing say 1 millisecond earlier and calculates instantaneous rate of change of angular velocity or angular acceleration (Alpha).
So that at any instant during the run the software uses this information to calculate engine Torque (I xAlpha). Angular velocity (Omega), and Power (Torque ×Omega. The information is presented in graph form as Power and Torque against Revs.
I don't 'get' the bit about taking 2 points on the torque curve calculating the gradient and using this
unrepresentative? figure to calculate horsepower. The software has the ability to produce coŕrect instantaneous values of Torque and Revs. and hence Power at every point of the 'run'.
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