Wow people have imagined that video for years and it looks exactly how you'd imagine it. Like Ian said you can see some of the fuel condense on the valve. That probably messes up the air-fuel ratio slightly. You can also see why you need spark advance. The spark fires and theres a delay before anything happens. I wish they would have kept the video going through the whole cycle but they cut it off right before the overlap. I wonder what knock would look like. I want one in my car. It would make tuning so much easier.