If you want to look for a formula to play with, I used to know this one but now I have absolutely NO clue. The formula would give an absolute crank output, by the numbers of course. Although things you needed were the engines airflow rates per RPM, VE percentage, bore and stroke, rod to stroke ratio, compression, etc.. All boils down to cylider pressure , peak and mean, over piston area to get peak and mean force on the crank journal centerline. Then you calculate that force on the stroke length per degrees of rotation and connecting rod to crank centerline angle. Yeah, the math covered several pages. I did the calculations ONE time 25 years ago. My calculations were of by like 3.2 hp. I left out the whole factor of frictional losses. I still carried an A on that piece. Thank the system for bell curves!! Really don't need all that crap taking space in your noodle bowl un less you work for a racing team or are an engineer. I'm a plumber! life is simple, shit rolls down hill, and if need be, we can pump it wherever we want!