So we had a mechanical engineer come into our a.p. physics class, and he did some cool stuff with liquid nitrogen and blew up some hydrogen balloons, but there is one thing he said that stuck with me. He said "who knows maybe the future of the engine is an helical engine that is 3-d printed (with metal of course) and uses a ball instead of a piston to compress the gas".............HOLY MOTHER OF F*CK I WOULD LOVE TO SEE THAT. Hell you know what, when I become an engineer, i'm going to try and make that. Somebody on here please print one out of abs and use air to test it out. But the idea is the ball would twist in the helical chamber, and the first explosion would push the ball and compress the gas on the other side of the ball. Then that will compress the next gas on the other side of the ball. The second side will then combust again and send the ball other way compressing freshly injected gas on the first side. Such a cool idea if you think about it.