Of course, there's a lot more to it, but that's the basics. We're sure you had a little animated diagram dancing around in your head the first time you really tried to understand the common Otto cycle. My mental flash player still fires up when I'm trying to figure out different cycles like the Atkinson. Wouldn't it be great to actually see inside the cylinder during combustion events? No, we didn't videotape our lawnmower with a Colortune plug -- this technique is far fancier.
Video and technique info after the jump
The imaging technique is known as Schlieren photography. Traditionally achieved with optics, this method is used to display variations in fluid density. When supersonic aircraft were under development, Schlieren photography was instrumental to solving the puzzle of flying faster than sound. This particular video uses modern digital techniques, rather than optics, no matter, it's still a really interesting peek inside the cylinder at the moment of combustion.