Beautiful view inside a spark ignited engine

I recently found an interesting video of the inside of a transparent spark ignited four stroke internal combustion engine, from the amazing SmarterEveryDay youtube channel. From a technical point of view, this animation is very interesting because we can clearly see where the spark plug is (the tiny blue dot) and how it works, i.e. how it triggers the combustion process. Moreover, from a more ‘thermodynamics’ standpoint, we can also approximately compare the speed of the flame front with the one of the piston. Clearly, the flame propagates itself in almost all the clearance volume while the piston just moves a little. The combustion process occurs then in an almost constant volume, and it’s why we usually suppose it as isochoric.