The 60+ year old marvel of technology that powers our flight is a nearly perfect match. Finicky, yes, but given the power, we get out of it’s few pounds, we can’t be terribly surprised.

Tuned Pipe

When the piston moving upward, it’s expelling exhaust, but a plug of incoming fuel/air mixture also goes right out the exhaust. In an effort to recoup this, clever designers built the expansion chamber. It uses a reflective wave pulse to push the fuel part of that exhaust back in the chamber. 

In the above GIF, notice a bit of green going out the exhaust then being pushed back in.

Image courtesy Wikipedia. It’s the most concise animation I’ve seen to date on understanding these things.