This is a simple question I have because I am looking at a particular engine cycle, and I can't seem to think of its name...thus it is very difficult to search for discussions of something you don't know the name of. I'll describe the cycle, if any one knows the name of the cycle please let me know, or remind me of what it is called. This is neither the Carnot cycle, nor the Otto Cycle,( aguable even more simlpe minded) In four steps on a Pressure-Volume Diagram it goes 1) Gas in piston (or the likes) expands at a constant pressure P1 2) Heat is allowed to escape, but volume is held fixed at V1 3) Gas in piston contracts at constant lower pressure P2 4) Heat is added while volume is held fixed at V2. (V2<V1) It looks like a square drawn on the P-V diagram. What is it's name?