A fire piston works on the same principle as a diesel engine - compression ignition. I'm a big fan of this kind of thermodynamics as it matches well to the theory and is very repeatable.

This fire syringe consists of a glass tube with a tightly-fitted piston inside the tube. When the piston is pushed down quickly, the air inside the tube is compressed. The quick compression of the air ...

With the cylinder now mostly filled with fresh air, the piston moves up again for the rest of the 118-mm compression stroke, with fuel injected along the way. A conventional 101-mm power stroke ...