Regarding the mathematics of the unusual shape and profile of the Wankel engine triangular rotor and combustion chamber housing, I'm reviewing a mathematics demonstration I have just come across but which has been on the internet for a few years but, like me, you may not have come across it before now. "Wankel Rotary Engine: Epitrochoidal Envelopes" by Tony Kelman on the Wolfram Demonstrations Project. http://demonstrations.wolfram.com/WankelRotaryEngineEpitrochoidalEnvelopes Review by Peter Dow If you think this video looks interesting, I highly recommend that you download the Wolfram CDF player software so that you can experiment with the features of Tony Kelman's demonstration. To quote Tony So selecting reference frame = epitrochoid allows the display of the familiar KKM Wankel engine and selecting reference frame = fixed centers shows Wankel's original DKM engine with rotating housing. You can slow the rotation animation down as well.. Looking at eccentricity ratios widely different from what we see in real Wankel engines is quite a revelation too. As if all that wasn't enough, you also get to download and look at Tony's open source code and in particular the maths equations he uses to generate the curves. Tony suggests some extensions to his demonstration. Well I have ideas of my own - I'd like to see computations of the areas between the curves representing the combustion chambers and a calculation of compression ratios for example. Unfortunately, I don't have the Mathematica developers software package which, unlike the free player I got to view the demo, you have to pay - A LOT - for. Excellent demonstration! Can't praise it highly enough!