Combustion Chamber Video

Stop what you're doing right now and go see this video taken from inside an operating engine. Except for the exhaust stroke (which the video skips over for some reason), this clip gives a remarkably informative view into the workings of the Otto cycle.

I was surprised by a couple of things. First, the intake valves (this is a 4-valve engine) spin so fast that they continue to rotate long after they've closed. In fact you can see the intake valve nearest the camera still spinning as the exhaust valve opens.

Another thing that caught my attention is the cyclonic flow pattern of the combusting fuel and air. If you look closely, the flames swirl in a counterclockwise fashion as seen by the camera. The coolest portion of burning charge (bright yellow-orange flame) seems always to be on the intake side of the cylinder (no surprise, I suppose).

Combustion is still underway as the exhaust valve opens. (You can see yellow flames still burning.) The rapid pressure drop as the valve opens makes the fire die down quickly.

This particular engine (I don't know what kind of engine it is) seems to have no detectable valve overlap. In fact, the intake valve doesn't even begin to open until the piston is already traveling downward on the intake stroke. This is extremely late valve opening, indicative of a turbocharged engine.

As they say, a picture is worth a thousand words.