I'm looking back at a previous thread here, in hopes of an answer regarding acceleration of engine RPM, and I have found something that might have answered it, the first post on this page: https://www.physicsforums.com/threads/accelerator-pedal-and-rpm.760572/page-4 (I suggest you don't go exploring this thread, it seems to go in circles.) However, I'm a little hazy on some variables and what they represent. First off, I understand that the variable I is a mass moment of inertia, but what of, exactly? The crankshaft? How would I go about calculating this? If I remember right from my physics class, shape is a factor in doing this: could I just assume the crankshaft is a solid cylinder (even though it's a bit more complex than one) and get a close approximation? And secondly, the variable alpha. Does that represent the acceleration of engine RPM itself, which can be directly seen on the tachometer; or is it of another component that is connected to the engine, which needs some math to find the actual RPM acceleration?