Useful Fuel Engine Platform by Guaibee

Here I present the 'Useful Fuel Engine Platform', with a bunch of designs that you may hopefully find useful... except under a closer look, some of the designs I've included on this platform is underperforming, so I've decided to leave them on there (not because I'm lazy or anything) as failed experiments, for investigation by interested individuals to hopefully make them work. The main goal of course is to provide a variety of engines for different people with different purposes, power demands and efficiency requirements, though I also hope that this engine platform can provide some insight into building compact and efficient engines as well. I will be updating this platform from time to time, adding in interesting designs I've made/found elsewhere. This platform was originally posted on the official forums. Updates will be specified over there, so pop in if you wish to check them out. The platform is divided into three levels: 'Red zone', where the designs with higher power density but still decent efficiency reside; 'Yellow zone', where the most common efficient engines can be found; and 'Green zone', the environmentalist's wet dream, where ultra efficient designs are displayed. I've also decided to add a 'Grey zone' for educational purposes, where I explain the principle behind all the inline turbos on this platform; 'Magenta zone' for smaller standalone engines that do not fit in the other zones; and a Black section on top of 'Red zone', with some fearsome beasts lurking... whatever would they be? Feel free to use the engines on the platform (until the original creators complain and I have to remove them or something), and give feedback and criticism (unless you want to mock me for doing fuel engines in the age ot steam, in which case go away). Also feel free to show me new engine designs for research and educational purposes.