I’m glad to see that this is getting some attention again 
I’d like to announce that I will no longer be updating the leaderboards. This is not because I’m lazy (OK, maybe a little) but because I’ve discovered that engine efficiency and car efficiency are not perfectly related, so a less efficient engine may actually result in a more efficient car. So while it’s good in general to strive to build engines that are powerful and efficient, it may actually be counterproductive to try to squeeze out every last drop of efficiency in hopes of getting a higher score.
This thread will remain a place to post your efficient and powerful engines, kind of like those 3000hp threads but actually meaningful 
I’m glad to see that most of you are doing this already, imposing limits on yourself and designing engines that are unique and still very efficient. Keep 'em coming guys! 
I’d also like to encourage you to put your engines up for download if you want. By sharing your designs we can help each other improve, and I may do a review on some engines that I find interesting!
For reference, my engines are available for download in this thread: Inline Designs - open source engines and consulting