Algodoo

Keeps getting better!

This engine has 8 HP/kg. 400 HP on a 50 kg package... Also uses only 1 collision layer per cylinder (A, B and C were used).
I've found out that the pistons knocked on the cylinder head, therefore making speed irregular and losing 30 HP. This way it gets to 5000 RPM stably and without any weird peaks before or after.
Maybe the single cylinder has the same problem, I dunno

If you wanna attach something to this engine, make sure to attach it on the counterweight-shaped polygon or on the frontmost circle. Below the circle there's a variable angle ignition circle thingy. If you attach something there you'll get 1 HP at most lol