I am learning about car basics. I found that engine is nothing but a system where heat energy is converted into up/down motion of the piston in the cylinder. Finally, this up/down motion is converted into rotary motion by locking the gear teethes against each other.
So, my understanding is that all that motion is available on the flywheel, when we shift gears, the rod connected from flywheel to the wheel changes the distance from the flywheel. This changes displacement and hence torque ( force * displacement) is changed. So, basically, piston is moving at the same speed only, when we accelerate the differential gears changes the speed. Is it correct? Or is it that when we accelerate even the piston starts moving faster? If yes, how is it possible, since the temperature or heat energy is same, we can't increase the temperature inside the cylinder suddenly on pressing the accelerator. Is my understanding correct here? Also, I see that in my car - the engine rpm doesn't keep changing. It changes a bit but not too much like odometer.